{-# LANGUAGE CPP                 #-}
{-# LANGUAGE DataKinds           #-}
{-# LANGUAGE FlexibleContexts    #-}
{-# LANGUAGE RankNTypes          #-}
{-# LANGUAGE ScopedTypeVariables #-}
{-# LANGUAGE TypeFamilies        #-}
{-# LANGUAGE ViewPatterns        #-}

{-# OPTIONS_GHC -Wno-incomplete-uni-patterns #-}

{-
(c) The University of Glasgow 2006
(c) The GRASP/AQUA Project, Glasgow University, 1992-1998

-}

-- | Typechecking user-specified @MonoTypes@
module GHC.Tc.Gen.HsType (
        -- Type signatures
        kcClassSigType, tcClassSigType,
        tcHsSigType, tcHsSigWcType,
        tcHsPartialSigType,
        tcStandaloneKindSig,
        funsSigCtxt, addSigCtxt, pprSigCtxt,

        tcHsClsInstType,
        tcHsDeriv, tcDerivStrategy,
        tcHsTypeApp,
        UserTypeCtxt(..),
        bindImplicitTKBndrs_Tv, bindImplicitTKBndrs_Skol,
            bindImplicitTKBndrs_Q_Tv, bindImplicitTKBndrs_Q_Skol,
        bindExplicitTKBndrs_Tv, bindExplicitTKBndrs_Skol,
            bindExplicitTKBndrs_Q_Tv, bindExplicitTKBndrs_Q_Skol,

        bindOuterFamEqnTKBndrs, bindOuterFamEqnTKBndrs_Q_Tv,
        tcOuterTKBndrs, scopedSortOuter,
        bindOuterSigTKBndrs_Tv,
        tcExplicitTKBndrs,
        bindNamedWildCardBinders,

        -- Type checking type and class decls, and instances thereof
        bindTyClTyVars, tcFamTyPats,
        etaExpandAlgTyCon, tcbVisibilities,

          -- tyvars
        zonkAndScopedSort,

        -- Kind-checking types
        -- No kind generalisation, no checkValidType
        InitialKindStrategy(..),
        SAKS_or_CUSK(..),
        ContextKind(..),
        kcDeclHeader,
        tcHsLiftedType,   tcHsOpenType,
        tcHsLiftedTypeNC, tcHsOpenTypeNC,
        tcInferLHsType, tcInferLHsTypeKind, tcInferLHsTypeUnsaturated,
        tcCheckLHsType,
        tcHsContext, tcLHsPredType,

        kindGeneralizeAll, kindGeneralizeSome, kindGeneralizeNone,

        -- Sort-checking kinds
        tcLHsKindSig, checkDataKindSig, DataSort(..),
        checkClassKindSig,

        -- Multiplicity
        tcMult,

        -- Pattern type signatures
        tcHsPatSigType,
        HoleMode(..),

        -- Error messages
        funAppCtxt, addTyConFlavCtxt
   ) where

#include "HsVersions.h"

import GHC.Prelude

import GHC.Hs
import GHC.Rename.Utils
import GHC.Tc.Utils.Monad
import GHC.Tc.Types.Origin
import GHC.Core.Predicate
import GHC.Tc.Types.Constraint
import GHC.Tc.Utils.Env
import GHC.Tc.Utils.TcMType
import GHC.Tc.Validity
import GHC.Tc.Utils.Unify
import GHC.IfaceToCore
import GHC.Tc.Solver
import GHC.Tc.Utils.Zonk
import GHC.Core.TyCo.Rep
import GHC.Core.TyCo.Ppr
import GHC.Tc.Utils.TcType
import GHC.Tc.Utils.Instantiate ( tcInstInvisibleTyBinders, tcInstInvisibleTyBindersN,
                                  tcInstInvisibleTyBinder )
import GHC.Core.Type
import GHC.Builtin.Types.Prim
import GHC.Types.Name.Env
import GHC.Types.Name.Reader( lookupLocalRdrOcc )
import GHC.Types.Var
import GHC.Types.Var.Set
import GHC.Core.TyCon
import GHC.Core.ConLike
import GHC.Core.DataCon
import GHC.Core.Class
import GHC.Types.Name
-- import GHC.Types.Name.Set
import GHC.Types.Var.Env
import GHC.Builtin.Types
import GHC.Types.Basic
import GHC.Types.SrcLoc
import GHC.Types.Unique
import GHC.Types.Unique.FM
import GHC.Types.Unique.Set
import GHC.Utils.Misc
import GHC.Types.Unique.Supply
import GHC.Utils.Outputable
import GHC.Utils.Panic
import GHC.Data.FastString
import GHC.Builtin.Names hiding ( wildCardName )
import GHC.Driver.Session
import qualified GHC.LanguageExtensions as LangExt

import GHC.Data.Maybe
import GHC.Data.Bag( unitBag )
import Data.List ( find )
import Control.Monad

{-
        ----------------------------
                General notes
        ----------------------------

Unlike with expressions, type-checking types both does some checking and
desugars at the same time. This is necessary because we often want to perform
equality checks on the types right away, and it would be incredibly painful
to do this on un-desugared types. Luckily, desugared types are close enough
to HsTypes to make the error messages sane.

During type-checking, we perform as little validity checking as possible.
Generally, after type-checking, you will want to do validity checking, say
with GHC.Tc.Validity.checkValidType.

Validity checking
~~~~~~~~~~~~~~~~~
Some of the validity check could in principle be done by the kind checker,
but not all:

- During desugaring, we normalise by expanding type synonyms.  Only
  after this step can we check things like type-synonym saturation
  e.g.  type T k = k Int
        type S a = a
  Then (T S) is ok, because T is saturated; (T S) expands to (S Int);
  and then S is saturated.  This is a GHC extension.

- Similarly, also a GHC extension, we look through synonyms before complaining
  about the form of a class or instance declaration

- Ambiguity checks involve functional dependencies

Also, in a mutually recursive group of types, we can't look at the TyCon until we've
finished building the loop.  So to keep things simple, we postpone most validity
checking until step (3).

%************************************************************************
%*                                                                      *
              Check types AND do validity checking
*                                                                      *
************************************************************************

Note [Keeping implicitly quantified variables in order]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
When the user implicitly quantifies over variables (say, in a type
signature), we need to come up with some ordering on these variables.
This is done by bumping the TcLevel, bringing the tyvars into scope,
and then type-checking the thing_inside. The constraints are all
wrapped in an implication, which is then solved. Finally, we can
zonk all the binders and then order them with scopedSort.

It's critical to solve before zonking and ordering in order to uncover
any unifications. You might worry that this eager solving could cause
trouble elsewhere. I don't think it will. Because it will solve only
in an increased TcLevel, it can't unify anything that was mentioned
elsewhere. Additionally, we require that the order of implicitly
quantified variables is manifest by the scope of these variables, so
we're not going to learn more information later that will help order
these variables.

Note [Recipe for checking a signature]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Kind-checking a user-written signature requires several steps:

 0. Bump the TcLevel
 1.   Bind any lexically-scoped type variables.
 2.   Generate constraints.
 3. Solve constraints.
 4. Sort any implicitly-bound variables into dependency order
 5. Promote tyvars and/or kind-generalize.
 6. Zonk.
 7. Check validity.

Very similar steps also apply when kind-checking a type or class
declaration.

The general pattern looks something like this.  (But NB every
specific instance varies in one way or another!)

    do { (tclvl, wanted, (spec_tkvs, ty))
              <- pushLevelAndSolveEqualitiesX "tc_top_lhs_type" $
                 bindImplicitTKBndrs_Skol sig_vars              $
                 <kind-check the type>

       ; spec_tkvs <- zonkAndScopedSort spec_tkvs

       ; reportUnsolvedEqualities skol_info spec_tkvs tclvl wanted

       ; let ty1 = mkSpecForAllTys spec_tkvs ty
       ; kvs <- kindGeneralizeAll ty1

       ; final_ty <- zonkTcTypeToType (mkInfForAllTys kvs ty1)

       ; checkValidType final_ty

This pattern is repeated many times in GHC.Tc.Gen.HsType,
GHC.Tc.Gen.Sig, and GHC.Tc.TyCl, with variations.  In more detail:

* pushLevelAndSolveEqualitiesX (Step 0, step 3) bumps the TcLevel,
  calls the thing inside to generate constraints, solves those
  constraints as much as possible, returning the residual unsolved
  constraints in 'wanted'.

* bindImplicitTKBndrs_Skol (Step 1) binds the user-specified type
  variables E.g.  when kind-checking f :: forall a. F a -> a we must
  bring 'a' into scope before kind-checking (F a -> a)

* zonkAndScopedSort (Step 4) puts those user-specified variables in
  the dependency order.  (For "implicit" variables the order is no
  user-specified.  E.g.  forall (a::k1) (b::k2). blah k1 and k2 are
  implicitly brought into scope.

* reportUnsolvedEqualities (Step 3 continued) reports any unsolved
  equalities, carefully wrapping them in an implication that binds the
  skolems.  We can't do that in pushLevelAndSolveEqualitiesX because
  that function doesn't have access to the skolems.

* kindGeneralize (Step 5). See Note [Kind generalisation]

* The final zonkTcTypeToType must happen after promoting/generalizing,
  because promoting and generalizing fill in metavariables.


Doing Step 3 (constraint solving) eagerly (rather than building an
implication constraint and solving later) is necessary for several
reasons:

* Exactly as for Solver.simplifyInfer: when generalising, we solve all
  the constraints we can so that we don't have to quantify over them
  or, since we don't quantify over constraints in kinds, float them
  and inhibit generalisation.

* Most signatures also bring implicitly quantified variables into
  scope, and solving is necessary to get these in the right order
  (Step 4) see Note [Keeping implicitly quantified variables in
  order]).

Note [Kind generalisation]
~~~~~~~~~~~~~~~~~~~~~~~~~~
Step 5 of Note [Recipe for checking a signature], namely
kind-generalisation, is done by
    kindGeneraliseAll
    kindGeneraliseSome
    kindGeneraliseNone

Here, we have to deal with the fact that metatyvars generated in the
type will have a bumped TcLevel, because explicit foralls raise the
TcLevel. To avoid these variables from ever being visible in the
surrounding context, we must obey the following dictum:

  Every metavariable in a type must either be
    (A) generalized, or
    (B) promoted, or        See Note [Promotion in signatures]
    (C) a cause to error    See Note [Naughty quantification candidates]
                            in GHC.Tc.Utils.TcMType

There are three steps (look at kindGeneraliseSome):

1. candidateQTyVarsOfType finds the free variables of the type or kind,
   to generalise

2. filterConstrainedCandidates filters out candidates that appear
   in the unsolved 'wanteds', and promotes the ones that get filtered out
   thereby.

3. quantifyTyVars quantifies the remaining type variables

The kindGeneralize functions do not require pre-zonking; they zonk as they
go.

kindGeneraliseAll specialises for the case where step (2) is vacuous.
kindGeneraliseNone specialises for the case where we do no quantification,
but we must still promote.

If you are actually doing kind-generalization, you need to bump the
level before generating constraints, as we will only generalize
variables with a TcLevel higher than the ambient one.
Hence the "pushLevel" in pushLevelAndSolveEqualities.

Note [Promotion in signatures]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
If an unsolved metavariable in a signature is not generalized
(because we're not generalizing the construct -- e.g., pattern
sig -- or because the metavars are constrained -- see kindGeneralizeSome)
we need to promote to maintain (WantedTvInv) of Note [TcLevel invariants]
in GHC.Tc.Utils.TcType. Note that promotion is identical in effect to generalizing
and the reinstantiating with a fresh metavariable at the current level.
So in some sense, we generalize *all* variables, but then re-instantiate
some of them.

Here is an example of why we must promote:
  foo (x :: forall a. a -> Proxy b) = ...

In the pattern signature, `b` is unbound, and will thus be brought into
scope. We do not know its kind: it will be assigned kappa[2]. Note that
kappa is at TcLevel 2, because it is invented under a forall. (A priori,
the kind kappa might depend on `a`, so kappa rightly has a higher TcLevel
than the surrounding context.) This kappa cannot be solved for while checking
the pattern signature (which is not kind-generalized). When we are checking
the *body* of foo, though, we need to unify the type of x with the argument
type of bar. At this point, the ambient TcLevel is 1, and spotting a
matavariable with level 2 would violate the (WantedTvInv) invariant of
Note [TcLevel invariants]. So, instead of kind-generalizing,
we promote the metavariable to level 1. This is all done in kindGeneralizeNone.

-}

funsSigCtxt :: [LocatedN Name] -> UserTypeCtxt
-- Returns FunSigCtxt, with no redundant-context-reporting,
-- form a list of located names
funsSigCtxt :: [GenLocated SrcSpanAnnN Name] -> UserTypeCtxt
funsSigCtxt (L SrcSpanAnnN
_ Name
name1 : [GenLocated SrcSpanAnnN Name]
_) = Name -> Bool -> UserTypeCtxt
FunSigCtxt Name
name1 Bool
False
funsSigCtxt []              = String -> UserTypeCtxt
forall a. String -> a
panic String
"funSigCtxt"

addSigCtxt :: Outputable hs_ty => UserTypeCtxt -> LocatedA hs_ty -> TcM a -> TcM a
addSigCtxt :: forall hs_ty a.
Outputable hs_ty =>
UserTypeCtxt -> LocatedA hs_ty -> TcM a -> TcM a
addSigCtxt UserTypeCtxt
ctxt LocatedA hs_ty
hs_ty TcM a
thing_inside
  = SrcSpan -> TcM a -> TcM a
forall a. SrcSpan -> TcRn a -> TcRn a
setSrcSpan (LocatedA hs_ty -> SrcSpan
forall a e. GenLocated (SrcSpanAnn' a) e -> SrcSpan
getLocA LocatedA hs_ty
hs_ty) (TcM a -> TcM a) -> TcM a -> TcM a
forall a b. (a -> b) -> a -> b
$
    SDoc -> TcM a -> TcM a
forall a. SDoc -> TcM a -> TcM a
addErrCtxt (UserTypeCtxt -> LocatedA hs_ty -> SDoc
forall hs_ty.
Outputable hs_ty =>
UserTypeCtxt -> LocatedA hs_ty -> SDoc
pprSigCtxt UserTypeCtxt
ctxt LocatedA hs_ty
hs_ty) (TcM a -> TcM a) -> TcM a -> TcM a
forall a b. (a -> b) -> a -> b
$
    TcM a
thing_inside

pprSigCtxt :: Outputable hs_ty => UserTypeCtxt -> LocatedA hs_ty -> SDoc
-- (pprSigCtxt ctxt <extra> <type>)
-- prints    In the type signature for 'f':
--              f :: <type>
-- The <extra> is either empty or "the ambiguity check for"
pprSigCtxt :: forall hs_ty.
Outputable hs_ty =>
UserTypeCtxt -> LocatedA hs_ty -> SDoc
pprSigCtxt UserTypeCtxt
ctxt LocatedA hs_ty
hs_ty
  | Just Name
n <- UserTypeCtxt -> Maybe Name
isSigMaybe UserTypeCtxt
ctxt
  = SDoc -> Arity -> SDoc -> SDoc
hang (String -> SDoc
text String
"In the type signature:")
       Arity
2 (Name -> SDoc
forall a. OutputableBndr a => a -> SDoc
pprPrefixOcc Name
n SDoc -> SDoc -> SDoc
<+> SDoc
dcolon SDoc -> SDoc -> SDoc
<+> LocatedA hs_ty -> SDoc
forall a. Outputable a => a -> SDoc
ppr LocatedA hs_ty
hs_ty)

  | Bool
otherwise
  = SDoc -> Arity -> SDoc -> SDoc
hang (String -> SDoc
text String
"In" SDoc -> SDoc -> SDoc
<+> UserTypeCtxt -> SDoc
pprUserTypeCtxt UserTypeCtxt
ctxt SDoc -> SDoc -> SDoc
<> SDoc
colon)
       Arity
2 (LocatedA hs_ty -> SDoc
forall a. Outputable a => a -> SDoc
ppr LocatedA hs_ty
hs_ty)

tcHsSigWcType :: UserTypeCtxt -> LHsSigWcType GhcRn -> TcM Type
-- This one is used when we have a LHsSigWcType, but in
-- a place where wildcards aren't allowed. The renamer has
-- already checked this, so we can simply ignore it.
tcHsSigWcType :: UserTypeCtxt -> LHsSigWcType GhcRn -> TcM Type
tcHsSigWcType UserTypeCtxt
ctxt LHsSigWcType GhcRn
sig_ty = UserTypeCtxt -> LHsSigType GhcRn -> TcM Type
tcHsSigType UserTypeCtxt
ctxt (LHsSigWcType GhcRn -> LHsSigType GhcRn
forall pass. LHsSigWcType pass -> LHsSigType pass
dropWildCards LHsSigWcType GhcRn
sig_ty)

kcClassSigType :: [LocatedN Name] -> LHsSigType GhcRn -> TcM ()
-- This is a special form of tcClassSigType that is used during the
-- kind-checking phase to infer the kind of class variables. Cf. tc_lhs_sig_type.
-- Importantly, this does *not* kind-generalize. Consider
--   class SC f where
--     meth :: forall a (x :: f a). Proxy x -> ()
-- When instantiating Proxy with kappa, we must unify kappa := f a. But we're
-- still working out the kind of f, and thus f a will have a coercion in it.
-- Coercions block unification (Note [Equalities with incompatible kinds] in
-- TcCanonical) and so we fail to unify. If we try to kind-generalize, we'll
-- end up promoting kappa to the top level (because kind-generalization is
-- normally done right before adding a binding to the context), and then we
-- can't set kappa := f a, because a is local.
kcClassSigType :: [GenLocated SrcSpanAnnN Name] -> LHsSigType GhcRn -> TcM ()
kcClassSigType [GenLocated SrcSpanAnnN Name]
names
    sig_ty :: LHsSigType GhcRn
sig_ty@(L SrcSpanAnnA
_ (HsSig { sig_bndrs :: forall pass. HsSigType pass -> HsOuterSigTyVarBndrs pass
sig_bndrs = HsOuterSigTyVarBndrs GhcRn
hs_outer_bndrs, sig_body :: forall pass. HsSigType pass -> LHsType pass
sig_body = LHsType GhcRn
hs_ty }))
  = UserTypeCtxt
-> GenLocated SrcSpanAnnA (HsSigType GhcRn) -> TcM () -> TcM ()
forall hs_ty a.
Outputable hs_ty =>
UserTypeCtxt -> LocatedA hs_ty -> TcM a -> TcM a
addSigCtxt ([GenLocated SrcSpanAnnN Name] -> UserTypeCtxt
funsSigCtxt [GenLocated SrcSpanAnnN Name]
names) GenLocated SrcSpanAnnA (HsSigType GhcRn)
LHsSigType GhcRn
sig_ty (TcM () -> TcM ()) -> TcM () -> TcM ()
forall a b. (a -> b) -> a -> b
$
    do { (HsOuterTyVarBndrs Specificity GhcTc, Type)
_ <- HsOuterSigTyVarBndrs GhcRn
-> TcM Type -> TcM (HsOuterTyVarBndrs Specificity GhcTc, Type)
forall a.
HsOuterSigTyVarBndrs GhcRn
-> TcM a -> TcM (HsOuterTyVarBndrs Specificity GhcTc, a)
bindOuterSigTKBndrs_Tv HsOuterSigTyVarBndrs GhcRn
hs_outer_bndrs    (TcM Type -> TcM (HsOuterTyVarBndrs Specificity GhcTc, Type))
-> TcM Type -> TcM (HsOuterTyVarBndrs Specificity GhcTc, Type)
forall a b. (a -> b) -> a -> b
$
              LHsType GhcRn -> Type -> TcM Type
tcLHsType LHsType GhcRn
hs_ty Type
liftedTypeKind
       ; () -> TcM ()
forall (m :: * -> *) a. Monad m => a -> m a
return () }

tcClassSigType :: [LocatedN Name] -> LHsSigType GhcRn -> TcM Type
-- Does not do validity checking
tcClassSigType :: [GenLocated SrcSpanAnnN Name] -> LHsSigType GhcRn -> TcM Type
tcClassSigType [GenLocated SrcSpanAnnN Name]
names LHsSigType GhcRn
sig_ty
  = UserTypeCtxt
-> GenLocated SrcSpanAnnA (HsSigType GhcRn) -> TcM Type -> TcM Type
forall hs_ty a.
Outputable hs_ty =>
UserTypeCtxt -> LocatedA hs_ty -> TcM a -> TcM a
addSigCtxt UserTypeCtxt
sig_ctxt GenLocated SrcSpanAnnA (HsSigType GhcRn)
LHsSigType GhcRn
sig_ty (TcM Type -> TcM Type) -> TcM Type -> TcM Type
forall a b. (a -> b) -> a -> b
$
    do { (Implication
implic, Type
ty) <- SkolemInfo
-> LHsSigType GhcRn -> ContextKind -> TcM (Implication, Type)
tc_lhs_sig_type SkolemInfo
skol_info LHsSigType GhcRn
sig_ty (Type -> ContextKind
TheKind Type
liftedTypeKind)
       ; Implication -> TcM ()
emitImplication Implication
implic
       ; Type -> TcM Type
forall (m :: * -> *) a. Monad m => a -> m a
return Type
ty }
       -- Do not zonk-to-Type, nor perform a validity check
       -- We are in a knot with the class and associated types
       -- Zonking and validity checking is done by tcClassDecl
       --
       -- No need to fail here if the type has an error:
       --   If we're in the kind-checking phase, the solveEqualities
       --     in kcTyClGroup catches the error
       --   If we're in the type-checking phase, the solveEqualities
       --     in tcClassDecl1 gets it
       -- Failing fast here degrades the error message in, e.g., tcfail135:
       --   class Foo f where
       --     baa :: f a -> f
       -- If we fail fast, we're told that f has kind `k1` when we wanted `*`.
       -- It should be that f has kind `k2 -> *`, but we never get a chance
       -- to run the solver where the kind of f is touchable. This is
       -- painfully delicate.
  where
    sig_ctxt :: UserTypeCtxt
sig_ctxt = [GenLocated SrcSpanAnnN Name] -> UserTypeCtxt
funsSigCtxt [GenLocated SrcSpanAnnN Name]
names
    skol_info :: SkolemInfo
skol_info = UserTypeCtxt -> SkolemInfo
SigTypeSkol UserTypeCtxt
sig_ctxt

tcHsSigType :: UserTypeCtxt -> LHsSigType GhcRn -> TcM Type
-- Does validity checking
-- See Note [Recipe for checking a signature]
tcHsSigType :: UserTypeCtxt -> LHsSigType GhcRn -> TcM Type
tcHsSigType UserTypeCtxt
ctxt LHsSigType GhcRn
sig_ty
  = UserTypeCtxt
-> GenLocated SrcSpanAnnA (HsSigType GhcRn) -> TcM Type -> TcM Type
forall hs_ty a.
Outputable hs_ty =>
UserTypeCtxt -> LocatedA hs_ty -> TcM a -> TcM a
addSigCtxt UserTypeCtxt
ctxt GenLocated SrcSpanAnnA (HsSigType GhcRn)
LHsSigType GhcRn
sig_ty (TcM Type -> TcM Type) -> TcM Type -> TcM Type
forall a b. (a -> b) -> a -> b
$
    do { String -> SDoc -> TcM ()
traceTc String
"tcHsSigType {" (GenLocated SrcSpanAnnA (HsSigType GhcRn) -> SDoc
forall a. Outputable a => a -> SDoc
ppr GenLocated SrcSpanAnnA (HsSigType GhcRn)
LHsSigType GhcRn
sig_ty)

          -- Generalise here: see Note [Kind generalisation]
       ; (Implication
implic, Type
ty) <- SkolemInfo
-> LHsSigType GhcRn -> ContextKind -> TcM (Implication, Type)
tc_lhs_sig_type SkolemInfo
skol_info LHsSigType GhcRn
sig_ty  (UserTypeCtxt -> ContextKind
expectedKindInCtxt UserTypeCtxt
ctxt)

       -- Float out constraints, failing fast if not possible
       -- See Note [Failure in local type signatures] in GHC.Tc.Solver
       ; String -> SDoc -> TcM ()
traceTc String
"tcHsSigType 2" (Implication -> SDoc
forall a. Outputable a => a -> SDoc
ppr Implication
implic)
       ; WantedConstraints -> TcM ()
simplifyAndEmitFlatConstraints (Bag Implication -> WantedConstraints
mkImplicWC (Implication -> Bag Implication
forall a. a -> Bag a
unitBag Implication
implic))

       ; Type
ty <- Type -> TcM Type
zonkTcType Type
ty
       ; UserTypeCtxt -> Type -> TcM ()
checkValidType UserTypeCtxt
ctxt Type
ty
       ; String -> SDoc -> TcM ()
traceTc String
"end tcHsSigType }" (Type -> SDoc
forall a. Outputable a => a -> SDoc
ppr Type
ty)
       ; Type -> TcM Type
forall (m :: * -> *) a. Monad m => a -> m a
return Type
ty }
  where
    skol_info :: SkolemInfo
skol_info = UserTypeCtxt -> SkolemInfo
SigTypeSkol UserTypeCtxt
ctxt

tc_lhs_sig_type :: SkolemInfo -> LHsSigType GhcRn
               -> ContextKind -> TcM (Implication, TcType)
-- Kind-checks/desugars an 'LHsSigType',
--   solve equalities,
--   and then kind-generalizes.
-- This will never emit constraints, as it uses solveEqualities internally.
-- No validity checking or zonking
-- Returns also an implication for the unsolved constraints
tc_lhs_sig_type :: SkolemInfo
-> LHsSigType GhcRn -> ContextKind -> TcM (Implication, Type)
tc_lhs_sig_type SkolemInfo
skol_info (L SrcSpanAnnA
loc (HsSig { sig_bndrs :: forall pass. HsSigType pass -> HsOuterSigTyVarBndrs pass
sig_bndrs = HsOuterSigTyVarBndrs GhcRn
hs_outer_bndrs
                                       , sig_body :: forall pass. HsSigType pass -> LHsType pass
sig_body = LHsType GhcRn
hs_ty })) ContextKind
ctxt_kind
  = SrcSpanAnnA -> TcM (Implication, Type) -> TcM (Implication, Type)
forall ann a. SrcSpanAnn' ann -> TcRn a -> TcRn a
setSrcSpanA SrcSpanAnnA
loc (TcM (Implication, Type) -> TcM (Implication, Type))
-> TcM (Implication, Type) -> TcM (Implication, Type)
forall a b. (a -> b) -> a -> b
$
    do { (TcLevel
tc_lvl, WantedConstraints
wanted, (HsOuterTyVarBndrs Specificity GhcTc
outer_bndrs, Type
ty))
              <- String
-> TcM (HsOuterTyVarBndrs Specificity GhcTc, Type)
-> TcM
     (TcLevel, WantedConstraints,
      (HsOuterTyVarBndrs Specificity GhcTc, Type))
forall a. String -> TcM a -> TcM (TcLevel, WantedConstraints, a)
pushLevelAndSolveEqualitiesX String
"tc_lhs_sig_type" (TcM (HsOuterTyVarBndrs Specificity GhcTc, Type)
 -> TcM
      (TcLevel, WantedConstraints,
       (HsOuterTyVarBndrs Specificity GhcTc, Type)))
-> TcM (HsOuterTyVarBndrs Specificity GhcTc, Type)
-> TcM
     (TcLevel, WantedConstraints,
      (HsOuterTyVarBndrs Specificity GhcTc, Type))
forall a b. (a -> b) -> a -> b
$
                 -- See Note [Failure in local type signatures]
                 SkolemInfo
-> HsOuterSigTyVarBndrs GhcRn
-> TcM Type
-> TcM (HsOuterTyVarBndrs Specificity GhcTc, Type)
forall flag a.
OutputableBndrFlag flag 'Renamed =>
SkolemInfo
-> HsOuterTyVarBndrs flag GhcRn
-> TcM a
-> TcM (HsOuterTyVarBndrs flag GhcTc, a)
tcOuterTKBndrs SkolemInfo
skol_info HsOuterSigTyVarBndrs GhcRn
hs_outer_bndrs (TcM Type -> TcM (HsOuterTyVarBndrs Specificity GhcTc, Type))
-> TcM Type -> TcM (HsOuterTyVarBndrs Specificity GhcTc, Type)
forall a b. (a -> b) -> a -> b
$
                 do { Type
kind <- ContextKind -> TcM Type
newExpectedKind ContextKind
ctxt_kind
                    ; LHsType GhcRn -> Type -> TcM Type
tcLHsType LHsType GhcRn
hs_ty Type
kind }
       -- Any remaining variables (unsolved in the solveEqualities)
       -- should be in the global tyvars, and therefore won't be quantified

       ; String -> SDoc -> TcM ()
traceTc String
"tc_lhs_sig_type" (HsOuterSigTyVarBndrs GhcRn -> SDoc
forall a. Outputable a => a -> SDoc
ppr HsOuterSigTyVarBndrs GhcRn
hs_outer_bndrs SDoc -> SDoc -> SDoc
$$ HsOuterTyVarBndrs Specificity GhcTc -> SDoc
forall a. Outputable a => a -> SDoc
ppr HsOuterTyVarBndrs Specificity GhcTc
outer_bndrs)
       ; ([InvisTVBinder]
outer_tv_bndrs :: [InvisTVBinder]) <- HsOuterTyVarBndrs Specificity GhcTc -> TcM [InvisTVBinder]
scopedSortOuter HsOuterTyVarBndrs Specificity GhcTc
outer_bndrs

       ; let ty1 :: Type
ty1 = [InvisTVBinder] -> Type -> Type
mkInvisForAllTys [InvisTVBinder]
outer_tv_bndrs Type
ty

       ; [TyVar]
kvs <- WantedConstraints -> Type -> TcM [TyVar]
kindGeneralizeSome WantedConstraints
wanted Type
ty1

       -- Build an implication for any as-yet-unsolved kind equalities
       -- See Note [Skolem escape in type signatures]
       ; Implication
implic <- SkolemInfo
-> [TyVar] -> TcLevel -> WantedConstraints -> TcM Implication
buildTvImplication SkolemInfo
skol_info [TyVar]
kvs TcLevel
tc_lvl WantedConstraints
wanted

       ; (Implication, Type) -> TcM (Implication, Type)
forall (m :: * -> *) a. Monad m => a -> m a
return (Implication
implic, [TyVar] -> Type -> Type
mkInfForAllTys [TyVar]
kvs Type
ty1) }

{- Note [Skolem escape in type signatures]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
tcHsSigType is tricky.  Consider (T11142)
  foo :: forall b. (forall k (a :: k). SameKind a b) -> ()
This is ill-kinded because of a nested skolem-escape.

That will show up as an un-solvable constraint in the implication
returned by buildTvImplication in tc_lhs_sig_type.  See Note [Skolem
escape prevention] in GHC.Tc.Utils.TcType for why it is unsolvable
(the unification variable for b's kind is untouchable).

Then, in GHC.Tc.Solver.simplifyAndEmitFlatConstraints (called from tcHsSigType)
we'll try to float out the constraint, be unable to do so, and fail.
See GHC.Tc.Solver Note [Failure in local type signatures] for more
detail on this.

The separation between tcHsSigType and tc_lhs_sig_type is because
tcClassSigType wants to use the latter, but *not* fail fast, because
there are skolems from the class decl which are in scope; but it's fine
not to because tcClassDecl1 has a solveEqualities wrapped around all
the tcClassSigType calls.

That's why tcHsSigType does simplifyAndEmitFlatConstraints (which
fails fast) but tcClassSigType just does emitImplication (which does
not).  Ugh.

c.f. see also Note [Skolem escape and forall-types]. The difference
is that we don't need to simplify at a forall type, only at the
top level of a signature.
-}

-- Does validity checking and zonking.
tcStandaloneKindSig :: LStandaloneKindSig GhcRn -> TcM (Name, Kind)
tcStandaloneKindSig :: LStandaloneKindSig GhcRn -> TcM (Name, Type)
tcStandaloneKindSig (L SrcSpanAnnA
_ (StandaloneKindSig XStandaloneKindSig GhcRn
_ (L SrcSpanAnnN
_ Name
name) LHsSigType GhcRn
ksig))
  = UserTypeCtxt
-> GenLocated SrcSpanAnnA (HsSigType GhcRn)
-> TcM (Name, Type)
-> TcM (Name, Type)
forall hs_ty a.
Outputable hs_ty =>
UserTypeCtxt -> LocatedA hs_ty -> TcM a -> TcM a
addSigCtxt UserTypeCtxt
ctxt GenLocated SrcSpanAnnA (HsSigType GhcRn)
LHsSigType GhcRn
ksig (TcM (Name, Type) -> TcM (Name, Type))
-> TcM (Name, Type) -> TcM (Name, Type)
forall a b. (a -> b) -> a -> b
$
    do { Type
kind <- TypeOrKind -> UserTypeCtxt -> LHsSigType GhcRn -> TcM Type
tc_top_lhs_type TypeOrKind
KindLevel UserTypeCtxt
ctxt LHsSigType GhcRn
ksig
       ; UserTypeCtxt -> Type -> TcM ()
checkValidType UserTypeCtxt
ctxt Type
kind
       ; (Name, Type) -> TcM (Name, Type)
forall (m :: * -> *) a. Monad m => a -> m a
return (Name
name, Type
kind) }
  where
   ctxt :: UserTypeCtxt
ctxt = Name -> UserTypeCtxt
StandaloneKindSigCtxt Name
name

tcTopLHsType :: UserTypeCtxt -> LHsSigType GhcRn -> TcM Type
tcTopLHsType :: UserTypeCtxt -> LHsSigType GhcRn -> TcM Type
tcTopLHsType UserTypeCtxt
ctxt LHsSigType GhcRn
lsig_ty
  = TypeOrKind -> UserTypeCtxt -> LHsSigType GhcRn -> TcM Type
tc_top_lhs_type TypeOrKind
TypeLevel UserTypeCtxt
ctxt LHsSigType GhcRn
lsig_ty

tc_top_lhs_type :: TypeOrKind -> UserTypeCtxt -> LHsSigType GhcRn -> TcM Type
-- tc_top_lhs_type is used for kind-checking top-level LHsSigTypes where
--   we want to fully solve /all/ equalities, and report errors
-- Does zonking, but not validity checking because it's used
--   for things (like deriving and instances) that aren't
--   ordinary types
-- Used for both types and kinds
tc_top_lhs_type :: TypeOrKind -> UserTypeCtxt -> LHsSigType GhcRn -> TcM Type
tc_top_lhs_type TypeOrKind
tyki UserTypeCtxt
ctxt (L SrcSpanAnnA
loc sig_ty :: HsSigType GhcRn
sig_ty@(HsSig { sig_bndrs :: forall pass. HsSigType pass -> HsOuterSigTyVarBndrs pass
sig_bndrs = HsOuterSigTyVarBndrs GhcRn
hs_outer_bndrs
                                               , sig_body :: forall pass. HsSigType pass -> LHsType pass
sig_body = LHsType GhcRn
body }))
  = SrcSpanAnnA -> TcM Type -> TcM Type
forall ann a. SrcSpanAnn' ann -> TcRn a -> TcRn a
setSrcSpanA SrcSpanAnnA
loc (TcM Type -> TcM Type) -> TcM Type -> TcM Type
forall a b. (a -> b) -> a -> b
$
    do { String -> SDoc -> TcM ()
traceTc String
"tc_top_lhs_type {" (HsSigType GhcRn -> SDoc
forall a. Outputable a => a -> SDoc
ppr HsSigType GhcRn
sig_ty)
       ; (TcLevel
tclvl, WantedConstraints
wanted, (HsOuterTyVarBndrs Specificity GhcTc
outer_bndrs, Type
ty))
              <- String
-> TcM (HsOuterTyVarBndrs Specificity GhcTc, Type)
-> TcM
     (TcLevel, WantedConstraints,
      (HsOuterTyVarBndrs Specificity GhcTc, Type))
forall a. String -> TcM a -> TcM (TcLevel, WantedConstraints, a)
pushLevelAndSolveEqualitiesX String
"tc_top_lhs_type"    (TcM (HsOuterTyVarBndrs Specificity GhcTc, Type)
 -> TcM
      (TcLevel, WantedConstraints,
       (HsOuterTyVarBndrs Specificity GhcTc, Type)))
-> TcM (HsOuterTyVarBndrs Specificity GhcTc, Type)
-> TcM
     (TcLevel, WantedConstraints,
      (HsOuterTyVarBndrs Specificity GhcTc, Type))
forall a b. (a -> b) -> a -> b
$
                 SkolemInfo
-> HsOuterSigTyVarBndrs GhcRn
-> TcM Type
-> TcM (HsOuterTyVarBndrs Specificity GhcTc, Type)
forall flag a.
OutputableBndrFlag flag 'Renamed =>
SkolemInfo
-> HsOuterTyVarBndrs flag GhcRn
-> TcM a
-> TcM (HsOuterTyVarBndrs flag GhcTc, a)
tcOuterTKBndrs SkolemInfo
skol_info HsOuterSigTyVarBndrs GhcRn
hs_outer_bndrs (TcM Type -> TcM (HsOuterTyVarBndrs Specificity GhcTc, Type))
-> TcM Type -> TcM (HsOuterTyVarBndrs Specificity GhcTc, Type)
forall a b. (a -> b) -> a -> b
$
                 do { Type
kind <- ContextKind -> TcM Type
newExpectedKind (UserTypeCtxt -> ContextKind
expectedKindInCtxt UserTypeCtxt
ctxt)
                    ; TcTyMode -> LHsType GhcRn -> Type -> TcM Type
tc_lhs_type (TypeOrKind -> TcTyMode
mkMode TypeOrKind
tyki) LHsType GhcRn
body Type
kind }

       ; [InvisTVBinder]
outer_tv_bndrs <- HsOuterTyVarBndrs Specificity GhcTc -> TcM [InvisTVBinder]
scopedSortOuter HsOuterTyVarBndrs Specificity GhcTc
outer_bndrs
       ; let ty1 :: Type
ty1 = [InvisTVBinder] -> Type -> Type
mkInvisForAllTys [InvisTVBinder]
outer_tv_bndrs Type
ty

       ; [TyVar]
kvs <- Type -> TcM [TyVar]
kindGeneralizeAll Type
ty1  -- "All" because it's a top-level type
       ; SkolemInfo -> [TyVar] -> TcLevel -> WantedConstraints -> TcM ()
reportUnsolvedEqualities SkolemInfo
skol_info [TyVar]
kvs TcLevel
tclvl WantedConstraints
wanted

       ; ZonkEnv
ze       <- ZonkFlexi -> TcM ZonkEnv
mkEmptyZonkEnv ZonkFlexi
NoFlexi
       ; Type
final_ty <- ZonkEnv -> Type -> TcM Type
zonkTcTypeToTypeX ZonkEnv
ze ([TyVar] -> Type -> Type
mkInfForAllTys [TyVar]
kvs Type
ty1)
       ; String -> SDoc -> TcM ()
traceTc String
"tc_top_lhs_type }" ([SDoc] -> SDoc
vcat [HsSigType GhcRn -> SDoc
forall a. Outputable a => a -> SDoc
ppr HsSigType GhcRn
sig_ty, Type -> SDoc
forall a. Outputable a => a -> SDoc
ppr Type
final_ty])
       ; Type -> TcM Type
forall (m :: * -> *) a. Monad m => a -> m a
return Type
final_ty }
  where
    skol_info :: SkolemInfo
skol_info = UserTypeCtxt -> SkolemInfo
SigTypeSkol UserTypeCtxt
ctxt

-----------------
tcHsDeriv :: LHsSigType GhcRn -> TcM ([TyVar], Class, [Type], [Kind])
-- Like tcHsSigType, but for the ...deriving( C t1 ty2 ) clause
-- Returns the C, [ty1, ty2, and the kinds of C's remaining arguments
-- E.g.    class C (a::*) (b::k->k)
--         data T a b = ... deriving( C Int )
--    returns ([k], C, [k, Int], [k->k])
-- Return values are fully zonked
tcHsDeriv :: LHsSigType GhcRn -> TcM ([TyVar], Class, [Type], [Type])
tcHsDeriv LHsSigType GhcRn
hs_ty
  = do { Type
ty <- TcM Type -> TcM Type
forall r. TcM r -> TcM r
checkNoErrs (TcM Type -> TcM Type) -> TcM Type -> TcM Type
forall a b. (a -> b) -> a -> b
$  -- Avoid redundant error report
                              -- with "illegal deriving", below
               UserTypeCtxt -> LHsSigType GhcRn -> TcM Type
tcTopLHsType UserTypeCtxt
DerivClauseCtxt LHsSigType GhcRn
hs_ty
       ; let ([TyVar]
tvs, Type
pred)    = Type -> ([TyVar], Type)
splitForAllTyCoVars Type
ty
             ([Scaled Type]
kind_args, Type
_) = Type -> ([Scaled Type], Type)
splitFunTys (HasDebugCallStack => Type -> Type
Type -> Type
tcTypeKind Type
pred)
       ; case Type -> Maybe (Class, [Type])
getClassPredTys_maybe Type
pred of
           Just (Class
cls, [Type]
tys) -> ([TyVar], Class, [Type], [Type])
-> TcM ([TyVar], Class, [Type], [Type])
forall (m :: * -> *) a. Monad m => a -> m a
return ([TyVar]
tvs, Class
cls, [Type]
tys, (Scaled Type -> Type) -> [Scaled Type] -> [Type]
forall a b. (a -> b) -> [a] -> [b]
map Scaled Type -> Type
forall a. Scaled a -> a
scaledThing [Scaled Type]
kind_args)
           Maybe (Class, [Type])
Nothing -> SDoc -> TcM ([TyVar], Class, [Type], [Type])
forall a. SDoc -> TcM a
failWithTc (String -> SDoc
text String
"Illegal deriving item" SDoc -> SDoc -> SDoc
<+> SDoc -> SDoc
quotes (GenLocated SrcSpanAnnA (HsSigType GhcRn) -> SDoc
forall a. Outputable a => a -> SDoc
ppr GenLocated SrcSpanAnnA (HsSigType GhcRn)
LHsSigType GhcRn
hs_ty)) }

-- | Typecheck a deriving strategy. For most deriving strategies, this is a
-- no-op, but for the @via@ strategy, this requires typechecking the @via@ type.
tcDerivStrategy ::
     Maybe (LDerivStrategy GhcRn)
     -- ^ The deriving strategy
  -> TcM (Maybe (LDerivStrategy GhcTc), [TyVar])
     -- ^ The typechecked deriving strategy and the tyvars that it binds
     -- (if using 'ViaStrategy').
tcDerivStrategy :: Maybe (LDerivStrategy GhcRn)
-> TcM (Maybe (LDerivStrategy GhcTc), [TyVar])
tcDerivStrategy Maybe (LDerivStrategy GhcRn)
mb_lds
  = case Maybe (LDerivStrategy GhcRn)
mb_lds of
      Maybe (LDerivStrategy GhcRn)
Nothing -> Maybe (GenLocated SrcSpan (DerivStrategy GhcTc))
-> TcM (Maybe (GenLocated SrcSpan (DerivStrategy GhcTc)), [TyVar])
forall ds. ds -> TcM (ds, [TyVar])
boring_case Maybe (GenLocated SrcSpan (DerivStrategy GhcTc))
forall a. Maybe a
Nothing
      Just (L SrcSpan
loc DerivStrategy GhcRn
ds) ->
        SrcSpan
-> TcM (Maybe (LDerivStrategy GhcTc), [TyVar])
-> TcM (Maybe (LDerivStrategy GhcTc), [TyVar])
forall a. SrcSpan -> TcRn a -> TcRn a
setSrcSpan SrcSpan
loc (TcM (Maybe (LDerivStrategy GhcTc), [TyVar])
 -> TcM (Maybe (LDerivStrategy GhcTc), [TyVar]))
-> TcM (Maybe (LDerivStrategy GhcTc), [TyVar])
-> TcM (Maybe (LDerivStrategy GhcTc), [TyVar])
forall a b. (a -> b) -> a -> b
$ do
          (DerivStrategy GhcTc
ds', [TyVar]
tvs) <- DerivStrategy GhcRn -> TcM (DerivStrategy GhcTc, [TyVar])
tc_deriv_strategy DerivStrategy GhcRn
ds
          (Maybe (GenLocated SrcSpan (DerivStrategy GhcTc)), [TyVar])
-> TcM (Maybe (GenLocated SrcSpan (DerivStrategy GhcTc)), [TyVar])
forall (f :: * -> *) a. Applicative f => a -> f a
pure (GenLocated SrcSpan (DerivStrategy GhcTc)
-> Maybe (GenLocated SrcSpan (DerivStrategy GhcTc))
forall a. a -> Maybe a
Just (SrcSpan
-> DerivStrategy GhcTc -> GenLocated SrcSpan (DerivStrategy GhcTc)
forall l e. l -> e -> GenLocated l e
L SrcSpan
loc DerivStrategy GhcTc
ds'), [TyVar]
tvs)
  where
    tc_deriv_strategy :: DerivStrategy GhcRn
                      -> TcM (DerivStrategy GhcTc, [TyVar])
    tc_deriv_strategy :: DerivStrategy GhcRn -> TcM (DerivStrategy GhcTc, [TyVar])
tc_deriv_strategy (StockStrategy    XStockStrategy GhcRn
_)
                                     = DerivStrategy GhcTc -> TcM (DerivStrategy GhcTc, [TyVar])
forall ds. ds -> TcM (ds, [TyVar])
boring_case (XStockStrategy GhcTc -> DerivStrategy GhcTc
forall pass. XStockStrategy pass -> DerivStrategy pass
StockStrategy NoExtField
XStockStrategy GhcTc
noExtField)
    tc_deriv_strategy (AnyclassStrategy XAnyClassStrategy GhcRn
_)
                                     = DerivStrategy GhcTc -> TcM (DerivStrategy GhcTc, [TyVar])
forall ds. ds -> TcM (ds, [TyVar])
boring_case (XAnyClassStrategy GhcTc -> DerivStrategy GhcTc
forall pass. XAnyClassStrategy pass -> DerivStrategy pass
AnyclassStrategy NoExtField
XAnyClassStrategy GhcTc
noExtField)
    tc_deriv_strategy (NewtypeStrategy  XNewtypeStrategy GhcRn
_)
                                     = DerivStrategy GhcTc -> TcM (DerivStrategy GhcTc, [TyVar])
forall ds. ds -> TcM (ds, [TyVar])
boring_case (XNewtypeStrategy GhcTc -> DerivStrategy GhcTc
forall pass. XNewtypeStrategy pass -> DerivStrategy pass
NewtypeStrategy NoExtField
XNewtypeStrategy GhcTc
noExtField)
    tc_deriv_strategy (ViaStrategy XViaStrategy GhcRn
ty) = do
      Type
ty' <- TcM Type -> TcM Type
forall r. TcM r -> TcM r
checkNoErrs (TcM Type -> TcM Type) -> TcM Type -> TcM Type
forall a b. (a -> b) -> a -> b
$ UserTypeCtxt -> LHsSigType GhcRn -> TcM Type
tcTopLHsType UserTypeCtxt
DerivClauseCtxt LHsSigType GhcRn
XViaStrategy GhcRn
ty
      let ([TyVar]
via_tvs, Type
via_pred) = Type -> ([TyVar], Type)
splitForAllTyCoVars Type
ty'
      (DerivStrategy GhcTc, [TyVar])
-> TcM (DerivStrategy GhcTc, [TyVar])
forall (f :: * -> *) a. Applicative f => a -> f a
pure (XViaStrategy GhcTc -> DerivStrategy GhcTc
forall pass. XViaStrategy pass -> DerivStrategy pass
ViaStrategy Type
XViaStrategy GhcTc
via_pred, [TyVar]
via_tvs)

    boring_case :: ds -> TcM (ds, [TyVar])
    boring_case :: forall ds. ds -> TcM (ds, [TyVar])
boring_case ds
ds = (ds, [TyVar]) -> IOEnv (Env TcGblEnv TcLclEnv) (ds, [TyVar])
forall (f :: * -> *) a. Applicative f => a -> f a
pure (ds
ds, [])

tcHsClsInstType :: UserTypeCtxt    -- InstDeclCtxt or SpecInstCtxt
                -> LHsSigType GhcRn
                -> TcM Type
-- Like tcHsSigType, but for a class instance declaration
tcHsClsInstType :: UserTypeCtxt -> LHsSigType GhcRn -> TcM Type
tcHsClsInstType UserTypeCtxt
user_ctxt LHsSigType GhcRn
hs_inst_ty
  = SrcSpan -> TcM Type -> TcM Type
forall a. SrcSpan -> TcRn a -> TcRn a
setSrcSpan (GenLocated SrcSpanAnnA (HsSigType GhcRn) -> SrcSpan
forall a e. GenLocated (SrcSpanAnn' a) e -> SrcSpan
getLocA GenLocated SrcSpanAnnA (HsSigType GhcRn)
LHsSigType GhcRn
hs_inst_ty) (TcM Type -> TcM Type) -> TcM Type -> TcM Type
forall a b. (a -> b) -> a -> b
$
    do { -- Fail eagerly if tcTopLHsType fails.  We are at top level so
         -- these constraints will never be solved later. And failing
         -- eagerly avoids follow-on errors when checkValidInstance
         -- sees an unsolved coercion hole
         Type
inst_ty <- TcM Type -> TcM Type
forall r. TcM r -> TcM r
checkNoErrs (TcM Type -> TcM Type) -> TcM Type -> TcM Type
forall a b. (a -> b) -> a -> b
$
                    UserTypeCtxt -> LHsSigType GhcRn -> TcM Type
tcTopLHsType UserTypeCtxt
user_ctxt LHsSigType GhcRn
hs_inst_ty
       ; UserTypeCtxt -> LHsSigType GhcRn -> Type -> TcM ()
checkValidInstance UserTypeCtxt
user_ctxt LHsSigType GhcRn
hs_inst_ty Type
inst_ty
       ; Type -> TcM Type
forall (m :: * -> *) a. Monad m => a -> m a
return Type
inst_ty }

----------------------------------------------
-- | Type-check a visible type application
tcHsTypeApp :: LHsWcType GhcRn -> Kind -> TcM Type
-- See Note [Recipe for checking a signature] in GHC.Tc.Gen.HsType
tcHsTypeApp :: LHsWcType GhcRn -> Type -> TcM Type
tcHsTypeApp LHsWcType GhcRn
wc_ty Type
kind
  | HsWC { hswc_ext :: forall pass thing. HsWildCardBndrs pass thing -> XHsWC pass thing
hswc_ext = XHsWC GhcRn (LHsType GhcRn)
sig_wcs, hswc_body :: forall pass thing. HsWildCardBndrs pass thing -> thing
hswc_body = LHsType GhcRn
hs_ty } <- LHsWcType GhcRn
wc_ty
  = do { TcTyMode
mode <- TypeOrKind -> HoleMode -> TcM TcTyMode
mkHoleMode TypeOrKind
TypeLevel HoleMode
HM_VTA
                 -- HM_VTA: See Note [Wildcards in visible type application]
       ; Type
ty <- LHsType GhcRn -> TcM Type -> TcM Type
forall a. LHsType GhcRn -> TcM a -> TcM a
addTypeCtxt LHsType GhcRn
hs_ty                  (TcM Type -> TcM Type) -> TcM Type -> TcM Type
forall a b. (a -> b) -> a -> b
$
               String -> TcM Type -> TcM Type
forall a. String -> TcM a -> TcM a
solveEqualities String
"tcHsTypeApp" (TcM Type -> TcM Type) -> TcM Type -> TcM Type
forall a b. (a -> b) -> a -> b
$
               -- We are looking at a user-written type, very like a
               -- signature so we want to solve its equalities right now
               HsQTvsRn -> ([(Name, TyVar)] -> TcM Type) -> TcM Type
forall a. HsQTvsRn -> ([(Name, TyVar)] -> TcM a) -> TcM a
bindNamedWildCardBinders HsQTvsRn
XHsWC GhcRn (LHsType GhcRn)
sig_wcs (([(Name, TyVar)] -> TcM Type) -> TcM Type)
-> ([(Name, TyVar)] -> TcM Type) -> TcM Type
forall a b. (a -> b) -> a -> b
$ \ [(Name, TyVar)]
_ ->
               TcTyMode -> LHsType GhcRn -> Type -> TcM Type
tc_lhs_type TcTyMode
mode LHsType GhcRn
hs_ty Type
kind

       -- We do not kind-generalize type applications: we just
       -- instantiate with exactly what the user says.
       -- See Note [No generalization in type application]
       -- We still must call kindGeneralizeNone, though, according
       -- to Note [Recipe for checking a signature]
       ; Type -> TcM ()
kindGeneralizeNone Type
ty
       ; Type
ty <- Type -> TcM Type
zonkTcType Type
ty
       ; UserTypeCtxt -> Type -> TcM ()
checkValidType UserTypeCtxt
TypeAppCtxt Type
ty
       ; Type -> TcM Type
forall (m :: * -> *) a. Monad m => a -> m a
return Type
ty }

{- Note [Wildcards in visible type application]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
A HsWildCardBndrs's hswc_ext now only includes /named/ wildcards, so
any unnamed wildcards stay unchanged in hswc_body.  When called in
tcHsTypeApp, tcCheckLHsType will call emitAnonTypeHole
on these anonymous wildcards. However, this would trigger
error/warning when an anonymous wildcard is passed in as a visible type
argument, which we do not want because users should be able to write
@_ to skip a instantiating a type variable variable without fuss. The
solution is to switch the PartialTypeSignatures flags here to let the
typechecker know that it's checking a '@_' and do not emit hole
constraints on it.  See related Note [Wildcards in visible kind
application] and Note [The wildcard story for types] in GHC.Hs.Type

Ugh!

Note [No generalization in type application]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
We do not kind-generalize type applications. Imagine

  id @(Proxy Nothing)

If we kind-generalized, we would get

  id @(forall {k}. Proxy @(Maybe k) (Nothing @k))

which is very sneakily impredicative instantiation.

There is also the possibility of mentioning a wildcard
(`id @(Proxy _)`), which definitely should not be kind-generalized.

-}

tcFamTyPats :: TyCon
            -> HsTyPats GhcRn                -- Patterns
            -> TcM (TcType, TcKind)          -- (lhs_type, lhs_kind)
-- Check the LHS of a type/data family instance
-- e.g.   type instance F ty1 .. tyn = ...
-- Used for both type and data families
tcFamTyPats :: TyCon -> HsTyPats GhcRn -> TcM (Type, Type)
tcFamTyPats TyCon
fam_tc HsTyPats GhcRn
hs_pats
  = do { String -> SDoc -> TcM ()
traceTc String
"tcFamTyPats {" (SDoc -> TcM ()) -> SDoc -> TcM ()
forall a b. (a -> b) -> a -> b
$
         [SDoc] -> SDoc
vcat [ TyCon -> SDoc
forall a. Outputable a => a -> SDoc
ppr TyCon
fam_tc, String -> SDoc
text String
"arity:" SDoc -> SDoc -> SDoc
<+> Arity -> SDoc
forall a. Outputable a => a -> SDoc
ppr Arity
fam_arity ]

       ; TcTyMode
mode <- TypeOrKind -> HoleMode -> TcM TcTyMode
mkHoleMode TypeOrKind
TypeLevel HoleMode
HM_FamPat
                 -- HM_FamPat: See Note [Wildcards in family instances] in
                 -- GHC.Rename.Module
       ; let fun_ty :: Type
fun_ty = TyCon -> [Type] -> Type
mkTyConApp TyCon
fam_tc []
       ; (Type
fam_app, Type
res_kind) <- TcTyMode
-> LHsType GhcRn -> Type -> HsTyPats GhcRn -> TcM (Type, Type)
tcInferTyApps TcTyMode
mode GenLocated SrcSpanAnnA (HsType GhcRn)
LHsType GhcRn
lhs_fun Type
fun_ty HsTyPats GhcRn
hs_pats

       -- Hack alert: see Note [tcFamTyPats: zonking the result kind]
       ; Type
res_kind <- Type -> TcM Type
zonkTcType Type
res_kind

       ; String -> SDoc -> TcM ()
traceTc String
"End tcFamTyPats }" (SDoc -> TcM ()) -> SDoc -> TcM ()
forall a b. (a -> b) -> a -> b
$
         [SDoc] -> SDoc
vcat [ TyCon -> SDoc
forall a. Outputable a => a -> SDoc
ppr TyCon
fam_tc, String -> SDoc
text String
"res_kind:" SDoc -> SDoc -> SDoc
<+> Type -> SDoc
forall a. Outputable a => a -> SDoc
ppr Type
res_kind ]

       ; (Type, Type) -> TcM (Type, Type)
forall (m :: * -> *) a. Monad m => a -> m a
return (Type
fam_app, Type
res_kind) }
  where
    fam_name :: Name
fam_name  = TyCon -> Name
tyConName TyCon
fam_tc
    fam_arity :: Arity
fam_arity = TyCon -> Arity
tyConArity TyCon
fam_tc
    lhs_fun :: GenLocated SrcSpanAnnA (HsType GhcRn)
lhs_fun   = HsType GhcRn -> GenLocated SrcSpanAnnA (HsType GhcRn)
forall a an. a -> LocatedAn an a
noLocA (XTyVar GhcRn -> PromotionFlag -> LIdP GhcRn -> HsType GhcRn
forall pass.
XTyVar pass -> PromotionFlag -> LIdP pass -> HsType pass
HsTyVar XTyVar GhcRn
forall a. EpAnn a
noAnn PromotionFlag
NotPromoted (Name -> GenLocated SrcSpanAnnN Name
forall a an. a -> LocatedAn an a
noLocA Name
fam_name))

{- Note [tcFamTyPats: zonking the result kind]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Consider (#19250)
    F :: forall k. k -> k
    type instance F (x :: Constraint) = ()

The tricky point is this:
  is that () an empty type tuple (() :: Type), or
  an empty constraint tuple (() :: Constraint)?
We work this out in a hacky way, by looking at the expected kind:
see Note [Inferring tuple kinds].

In this case, we kind-check the RHS using the kind gotten from the LHS:
see the call to tcCheckLHsType in tcTyFamInstEqnGuts in GHC.Tc.Tycl.

But we want the kind from the LHS to be /zonked/, so that when
kind-checking the RHS (tcCheckLHsType) we can "see" what we learned
from kind-checking the LHS (tcFamTyPats).  In our example above, the
type of the LHS is just `kappa` (by instantiating the forall k), but
then we learn (from x::Constraint) that kappa ~ Constraint.  We want
that info when kind-checking the RHS.

Easy solution: just zonk that return kind.  Of course this won't help
if there is lots of type-family reduction to do, but it works fine in
common cases.
-}


{-
************************************************************************
*                                                                      *
            The main kind checker: no validity checks here
*                                                                      *
************************************************************************
-}

---------------------------
tcHsOpenType, tcHsLiftedType,
  tcHsOpenTypeNC, tcHsLiftedTypeNC :: LHsType GhcRn -> TcM TcType
-- Used for type signatures
-- Do not do validity checking
tcHsOpenType :: LHsType GhcRn -> TcM Type
tcHsOpenType   LHsType GhcRn
hs_ty = LHsType GhcRn -> TcM Type -> TcM Type
forall a. LHsType GhcRn -> TcM a -> TcM a
addTypeCtxt LHsType GhcRn
hs_ty (TcM Type -> TcM Type) -> TcM Type -> TcM Type
forall a b. (a -> b) -> a -> b
$ LHsType GhcRn -> TcM Type
tcHsOpenTypeNC LHsType GhcRn
hs_ty
tcHsLiftedType :: LHsType GhcRn -> TcM Type
tcHsLiftedType LHsType GhcRn
hs_ty = LHsType GhcRn -> TcM Type -> TcM Type
forall a. LHsType GhcRn -> TcM a -> TcM a
addTypeCtxt LHsType GhcRn
hs_ty (TcM Type -> TcM Type) -> TcM Type -> TcM Type
forall a b. (a -> b) -> a -> b
$ LHsType GhcRn -> TcM Type
tcHsLiftedTypeNC LHsType GhcRn
hs_ty

tcHsOpenTypeNC :: LHsType GhcRn -> TcM Type
tcHsOpenTypeNC   LHsType GhcRn
hs_ty = do { Type
ek <- TcM Type
newOpenTypeKind; LHsType GhcRn -> Type -> TcM Type
tcLHsType LHsType GhcRn
hs_ty Type
ek }
tcHsLiftedTypeNC :: LHsType GhcRn -> TcM Type
tcHsLiftedTypeNC LHsType GhcRn
hs_ty = LHsType GhcRn -> Type -> TcM Type
tcLHsType LHsType GhcRn
hs_ty Type
liftedTypeKind

-- Like tcHsType, but takes an expected kind
tcCheckLHsType :: LHsType GhcRn -> ContextKind -> TcM TcType
tcCheckLHsType :: LHsType GhcRn -> ContextKind -> TcM Type
tcCheckLHsType LHsType GhcRn
hs_ty ContextKind
exp_kind
  = LHsType GhcRn -> TcM Type -> TcM Type
forall a. LHsType GhcRn -> TcM a -> TcM a
addTypeCtxt LHsType GhcRn
hs_ty (TcM Type -> TcM Type) -> TcM Type -> TcM Type
forall a b. (a -> b) -> a -> b
$
    do { Type
ek <- ContextKind -> TcM Type
newExpectedKind ContextKind
exp_kind
       ; LHsType GhcRn -> Type -> TcM Type
tcLHsType LHsType GhcRn
hs_ty Type
ek }

tcInferLHsType :: LHsType GhcRn -> TcM TcType
tcInferLHsType :: LHsType GhcRn -> TcM Type
tcInferLHsType LHsType GhcRn
hs_ty
  = do { (Type
ty,Type
_kind) <- LHsType GhcRn -> TcM (Type, Type)
tcInferLHsTypeKind LHsType GhcRn
hs_ty
       ; Type -> TcM Type
forall (m :: * -> *) a. Monad m => a -> m a
return Type
ty }

tcInferLHsTypeKind :: LHsType GhcRn -> TcM (TcType, TcKind)
-- Called from outside: set the context
-- Eagerly instantiate any trailing invisible binders
tcInferLHsTypeKind :: LHsType GhcRn -> TcM (Type, Type)
tcInferLHsTypeKind lhs_ty :: LHsType GhcRn
lhs_ty@(L SrcSpanAnnA
loc HsType GhcRn
hs_ty)
  = LHsType GhcRn -> TcM (Type, Type) -> TcM (Type, Type)
forall a. LHsType GhcRn -> TcM a -> TcM a
addTypeCtxt LHsType GhcRn
lhs_ty (TcM (Type, Type) -> TcM (Type, Type))
-> TcM (Type, Type) -> TcM (Type, Type)
forall a b. (a -> b) -> a -> b
$
    SrcSpanAnnA -> TcM (Type, Type) -> TcM (Type, Type)
forall ann a. SrcSpanAnn' ann -> TcRn a -> TcRn a
setSrcSpanA SrcSpanAnnA
loc    (TcM (Type, Type) -> TcM (Type, Type))
-> TcM (Type, Type) -> TcM (Type, Type)
forall a b. (a -> b) -> a -> b
$  -- Cover the tcInstInvisibleTyBinders
    do { (Type
res_ty, Type
res_kind) <- TcTyMode -> HsType GhcRn -> TcM (Type, Type)
tc_infer_hs_type TcTyMode
typeLevelMode HsType GhcRn
hs_ty
       ; Type -> Type -> TcM (Type, Type)
tcInstInvisibleTyBinders Type
res_ty Type
res_kind }
  -- See Note [Do not always instantiate eagerly in types]

-- Used to check the argument of GHCi :kind
-- Allow and report wildcards, e.g. :kind T _
-- Do not saturate family applications: see Note [Dealing with :kind]
-- Does not instantiate eagerly; See Note [Do not always instantiate eagerly in types]
tcInferLHsTypeUnsaturated :: LHsType GhcRn -> TcM (TcType, TcKind)
tcInferLHsTypeUnsaturated :: LHsType GhcRn -> TcM (Type, Type)
tcInferLHsTypeUnsaturated LHsType GhcRn
hs_ty
  = LHsType GhcRn -> TcM (Type, Type) -> TcM (Type, Type)
forall a. LHsType GhcRn -> TcM a -> TcM a
addTypeCtxt LHsType GhcRn
hs_ty (TcM (Type, Type) -> TcM (Type, Type))
-> TcM (Type, Type) -> TcM (Type, Type)
forall a b. (a -> b) -> a -> b
$
    do { TcTyMode
mode <- TypeOrKind -> HoleMode -> TcM TcTyMode
mkHoleMode TypeOrKind
TypeLevel HoleMode
HM_Sig  -- Allow and report holes
       ; case HsType GhcRn -> Maybe (LHsType GhcRn, HsTyPats GhcRn)
splitHsAppTys (GenLocated SrcSpanAnnA (HsType GhcRn) -> HsType GhcRn
forall l e. GenLocated l e -> e
unLoc GenLocated SrcSpanAnnA (HsType GhcRn)
LHsType GhcRn
hs_ty) of
           Just (LHsType GhcRn
hs_fun_ty, HsTyPats GhcRn
hs_args)
              -> do { (Type
fun_ty, Type
_ki) <- TcTyMode -> LHsType GhcRn -> TcM (Type, Type)
tcInferTyAppHead TcTyMode
mode LHsType GhcRn
hs_fun_ty
                    ; TcTyMode
-> LHsType GhcRn -> Type -> HsTyPats GhcRn -> TcM (Type, Type)
tcInferTyApps_nosat TcTyMode
mode LHsType GhcRn
hs_fun_ty Type
fun_ty HsTyPats GhcRn
hs_args }
                      -- Notice the 'nosat'; do not instantiate trailing
                      -- invisible arguments of a type family.
                      -- See Note [Dealing with :kind]
           Maybe (LHsType GhcRn, HsTyPats GhcRn)
Nothing -> TcTyMode -> LHsType GhcRn -> TcM (Type, Type)
tc_infer_lhs_type TcTyMode
mode LHsType GhcRn
hs_ty }

{- Note [Dealing with :kind]
~~~~~~~~~~~~~~~~~~~~~~~~~~~
Consider this GHCi command
  ghci> type family F :: Either j k
  ghci> :kind F
  F :: forall {j,k}. Either j k

We will only get the 'forall' if we /refrain/ from saturating those
invisible binders. But generally we /do/ saturate those invisible
binders (see tcInferTyApps), and we want to do so for nested application
even in GHCi.  Consider for example (#16287)
  ghci> type family F :: k
  ghci> data T :: (forall k. k) -> Type
  ghci> :kind T F
We want to reject this. It's just at the very top level that we want
to switch off saturation.

So tcInferLHsTypeUnsaturated does a little special case for top level
applications.  Actually the common case is a bare variable, as above.

Note [Do not always instantiate eagerly in types]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Terms are eagerly instantiated. This means that if you say

  x = id

then `id` gets instantiated to have type alpha -> alpha. The variable
alpha is then unconstrained and regeneralized. But we cannot do this
in types, as we have no type-level lambda. So, when we are sure
that we will not want to regeneralize later -- because we are done
checking a type, for example -- we can instantiate. But we do not
instantiate at variables, nor do we in tcInferLHsTypeUnsaturated,
which is used by :kind in GHCi.

************************************************************************
*                                                                      *
      Type-checking modes
*                                                                      *
************************************************************************

The kind-checker is parameterised by a TcTyMode, which contains some
information about where we're checking a type.

The renamer issues errors about what it can. All errors issued here must
concern things that the renamer can't handle.

-}

tcMult :: HsArrow GhcRn -> TcM Mult
tcMult :: HsArrow GhcRn -> TcM Type
tcMult HsArrow GhcRn
hc = TcTyMode -> HsArrow GhcRn -> TcM Type
tc_mult TcTyMode
typeLevelMode HsArrow GhcRn
hc

-- | Info about the context in which we're checking a type. Currently,
-- differentiates only between types and kinds, but this will likely
-- grow, at least to include the distinction between patterns and
-- not-patterns.
--
-- To find out where the mode is used, search for 'mode_tyki'
--
-- This data type is purely local, not exported from this module
data TcTyMode
  = TcTyMode { TcTyMode -> TypeOrKind
mode_tyki :: TypeOrKind
             , TcTyMode -> HoleInfo
mode_holes :: HoleInfo   }

-- See Note [Levels for wildcards]
-- Nothing <=> no wildcards expected
type HoleInfo = Maybe (TcLevel, HoleMode)

-- HoleMode says how to treat the occurrences
-- of anonymous wildcards; see tcAnonWildCardOcc
data HoleMode = HM_Sig      -- Partial type signatures: f :: _ -> Int
              | HM_FamPat   -- Family instances: F _ Int = Bool
              | HM_VTA      -- Visible type and kind application:
                            --   f @(Maybe _)
                            --   Maybe @(_ -> _)
              | HM_TyAppPat -- Visible type applications in patterns:
                            --   foo (Con @_ @t x) = ...
                            --   case x of Con @_ @t v -> ...

mkMode :: TypeOrKind -> TcTyMode
mkMode :: TypeOrKind -> TcTyMode
mkMode TypeOrKind
tyki = TcTyMode { mode_tyki :: TypeOrKind
mode_tyki = TypeOrKind
tyki, mode_holes :: HoleInfo
mode_holes = HoleInfo
forall a. Maybe a
Nothing }

typeLevelMode, kindLevelMode :: TcTyMode
-- These modes expect no wildcards (holes) in the type
kindLevelMode :: TcTyMode
kindLevelMode = TypeOrKind -> TcTyMode
mkMode TypeOrKind
KindLevel
typeLevelMode :: TcTyMode
typeLevelMode = TypeOrKind -> TcTyMode
mkMode TypeOrKind
TypeLevel

mkHoleMode :: TypeOrKind -> HoleMode -> TcM TcTyMode
mkHoleMode :: TypeOrKind -> HoleMode -> TcM TcTyMode
mkHoleMode TypeOrKind
tyki HoleMode
hm
  = do { TcLevel
lvl <- TcM TcLevel
getTcLevel
       ; TcTyMode -> TcM TcTyMode
forall (m :: * -> *) a. Monad m => a -> m a
return (TcTyMode { mode_tyki :: TypeOrKind
mode_tyki  = TypeOrKind
tyki
                          , mode_holes :: HoleInfo
mode_holes = (TcLevel, HoleMode) -> HoleInfo
forall a. a -> Maybe a
Just (TcLevel
lvl,HoleMode
hm) }) }

instance Outputable HoleMode where
  ppr :: HoleMode -> SDoc
ppr HoleMode
HM_Sig      = String -> SDoc
text String
"HM_Sig"
  ppr HoleMode
HM_FamPat   = String -> SDoc
text String
"HM_FamPat"
  ppr HoleMode
HM_VTA      = String -> SDoc
text String
"HM_VTA"
  ppr HoleMode
HM_TyAppPat = String -> SDoc
text String
"HM_TyAppPat"

instance Outputable TcTyMode where
  ppr :: TcTyMode -> SDoc
ppr (TcTyMode { mode_tyki :: TcTyMode -> TypeOrKind
mode_tyki = TypeOrKind
tyki, mode_holes :: TcTyMode -> HoleInfo
mode_holes = HoleInfo
hm })
    = String -> SDoc
text String
"TcTyMode" SDoc -> SDoc -> SDoc
<+> SDoc -> SDoc
braces ([SDoc] -> SDoc
sep [ TypeOrKind -> SDoc
forall a. Outputable a => a -> SDoc
ppr TypeOrKind
tyki SDoc -> SDoc -> SDoc
<> SDoc
comma
                                      , HoleInfo -> SDoc
forall a. Outputable a => a -> SDoc
ppr HoleInfo
hm ])

{-
Note [Bidirectional type checking]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
In expressions, whenever we see a polymorphic identifier, say `id`, we are
free to instantiate it with metavariables, knowing that we can always
re-generalize with type-lambdas when necessary. For example:

  rank2 :: (forall a. a -> a) -> ()
  x = rank2 id

When checking the body of `x`, we can instantiate `id` with a metavariable.
Then, when we're checking the application of `rank2`, we notice that we really
need a polymorphic `id`, and then re-generalize over the unconstrained
metavariable.

In types, however, we're not so lucky, because *we cannot re-generalize*!
There is no lambda. So, we must be careful only to instantiate at the last
possible moment, when we're sure we're never going to want the lost polymorphism
again. This is done in calls to tcInstInvisibleTyBinders.

To implement this behavior, we use bidirectional type checking, where we
explicitly think about whether we know the kind of the type we're checking
or not. Note that there is a difference between not knowing a kind and
knowing a metavariable kind: the metavariables are TauTvs, and cannot become
forall-quantified kinds. Previously (before dependent types), there were
no higher-rank kinds, and so we could instantiate early and be sure that
no types would have polymorphic kinds, and so we could always assume that
the kind of a type was a fresh metavariable. Not so anymore, thus the
need for two algorithms.

For HsType forms that can never be kind-polymorphic, we implement only the
"down" direction, where we safely assume a metavariable kind. For HsType forms
that *can* be kind-polymorphic, we implement just the "up" (functions with
"infer" in their name) version, as we gain nothing by also implementing the
"down" version.

Note [Future-proofing the type checker]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
As discussed in Note [Bidirectional type checking], each HsType form is
handled in *either* tc_infer_hs_type *or* tc_hs_type. These functions
are mutually recursive, so that either one can work for any type former.
But, we want to make sure that our pattern-matches are complete. So,
we have a bunch of repetitive code just so that we get warnings if we're
missing any patterns.

-}

------------------------------------------
-- | Check and desugar a type, returning the core type and its
-- possibly-polymorphic kind. Much like 'tcInferRho' at the expression
-- level.
tc_infer_lhs_type :: TcTyMode -> LHsType GhcRn -> TcM (TcType, TcKind)
tc_infer_lhs_type :: TcTyMode -> LHsType GhcRn -> TcM (Type, Type)
tc_infer_lhs_type TcTyMode
mode (L SrcSpanAnnA
span HsType GhcRn
ty)
  = SrcSpanAnnA -> TcM (Type, Type) -> TcM (Type, Type)
forall ann a. SrcSpanAnn' ann -> TcRn a -> TcRn a
setSrcSpanA SrcSpanAnnA
span (TcM (Type, Type) -> TcM (Type, Type))
-> TcM (Type, Type) -> TcM (Type, Type)
forall a b. (a -> b) -> a -> b
$
    TcTyMode -> HsType GhcRn -> TcM (Type, Type)
tc_infer_hs_type TcTyMode
mode HsType GhcRn
ty

---------------------------
-- | Call 'tc_infer_hs_type' and check its result against an expected kind.
tc_infer_hs_type_ek :: HasDebugCallStack => TcTyMode -> HsType GhcRn -> TcKind -> TcM TcType
tc_infer_hs_type_ek :: HasDebugCallStack => TcTyMode -> HsType GhcRn -> Type -> TcM Type
tc_infer_hs_type_ek TcTyMode
mode HsType GhcRn
hs_ty Type
ek
  = do { (Type
ty, Type
k) <- TcTyMode -> HsType GhcRn -> TcM (Type, Type)
tc_infer_hs_type TcTyMode
mode HsType GhcRn
hs_ty
       ; HasDebugCallStack =>
HsType GhcRn -> Type -> Type -> Type -> TcM Type
HsType GhcRn -> Type -> Type -> Type -> TcM Type
checkExpectedKind HsType GhcRn
hs_ty Type
ty Type
k Type
ek }

---------------------------
-- | Infer the kind of a type and desugar. This is the "up" type-checker,
-- as described in Note [Bidirectional type checking]
tc_infer_hs_type :: TcTyMode -> HsType GhcRn -> TcM (TcType, TcKind)

tc_infer_hs_type :: TcTyMode -> HsType GhcRn -> TcM (Type, Type)
tc_infer_hs_type TcTyMode
mode (HsParTy XParTy GhcRn
_ LHsType GhcRn
t)
  = TcTyMode -> LHsType GhcRn -> TcM (Type, Type)
tc_infer_lhs_type TcTyMode
mode LHsType GhcRn
t

tc_infer_hs_type TcTyMode
mode HsType GhcRn
ty
  | Just (LHsType GhcRn
hs_fun_ty, HsTyPats GhcRn
hs_args) <- HsType GhcRn -> Maybe (LHsType GhcRn, HsTyPats GhcRn)
splitHsAppTys HsType GhcRn
ty
  = do { (Type
fun_ty, Type
_ki) <- TcTyMode -> LHsType GhcRn -> TcM (Type, Type)
tcInferTyAppHead TcTyMode
mode LHsType GhcRn
hs_fun_ty
       ; TcTyMode
-> LHsType GhcRn -> Type -> HsTyPats GhcRn -> TcM (Type, Type)
tcInferTyApps TcTyMode
mode LHsType GhcRn
hs_fun_ty Type
fun_ty HsTyPats GhcRn
hs_args }

tc_infer_hs_type TcTyMode
mode (HsKindSig XKindSig GhcRn
_ LHsType GhcRn
ty LHsType GhcRn
sig)
  = do { let mode' :: TcTyMode
mode' = TcTyMode
mode { mode_tyki :: TypeOrKind
mode_tyki = TypeOrKind
KindLevel }
       ; Type
sig' <- TcTyMode -> UserTypeCtxt -> LHsType GhcRn -> TcM Type
tc_lhs_kind_sig TcTyMode
mode' UserTypeCtxt
KindSigCtxt LHsType GhcRn
sig
                 -- We must typecheck the kind signature, and solve all
                 -- its equalities etc; from this point on we may do
                 -- things like instantiate its foralls, so it needs
                 -- to be fully determined (#14904)
       ; String -> SDoc -> TcM ()
traceTc String
"tc_infer_hs_type:sig" (GenLocated SrcSpanAnnA (HsType GhcRn) -> SDoc
forall a. Outputable a => a -> SDoc
ppr GenLocated SrcSpanAnnA (HsType GhcRn)
LHsType GhcRn
ty SDoc -> SDoc -> SDoc
$$ Type -> SDoc
forall a. Outputable a => a -> SDoc
ppr Type
sig')
       ; Type
ty' <- TcTyMode -> LHsType GhcRn -> Type -> TcM Type
tc_lhs_type TcTyMode
mode LHsType GhcRn
ty Type
sig'
       ; (Type, Type) -> TcM (Type, Type)
forall (m :: * -> *) a. Monad m => a -> m a
return (Type
ty', Type
sig') }

-- HsSpliced is an annotation produced by 'GHC.Rename.Splice.rnSpliceType' to communicate
-- the splice location to the typechecker. Here we skip over it in order to have
-- the same kind inferred for a given expression whether it was produced from
-- splices or not.
--
-- See Note [Delaying modFinalizers in untyped splices].
tc_infer_hs_type TcTyMode
mode (HsSpliceTy XSpliceTy GhcRn
_ (HsSpliced XSpliced GhcRn
_ ThModFinalizers
_ (HsSplicedTy HsType GhcRn
ty)))
  = TcTyMode -> HsType GhcRn -> TcM (Type, Type)
tc_infer_hs_type TcTyMode
mode HsType GhcRn
ty

tc_infer_hs_type TcTyMode
mode (HsDocTy XDocTy GhcRn
_ LHsType GhcRn
ty LHsDocString
_) = TcTyMode -> LHsType GhcRn -> TcM (Type, Type)
tc_infer_lhs_type TcTyMode
mode LHsType GhcRn
ty

-- See Note [Typechecking HsCoreTys]
tc_infer_hs_type TcTyMode
_ (XHsType XXType GhcRn
ty)
  = do TcLclEnv
env <- TcRnIf TcGblEnv TcLclEnv TcLclEnv
forall gbl lcl. TcRnIf gbl lcl lcl
getLclEnv
       -- Raw uniques since we go from NameEnv to TvSubstEnv.
       let subst_prs :: [(Unique, TcTyVar)]
           subst_prs :: [(Unique, TyVar)]
subst_prs = [ (Name -> Unique
forall a. Uniquable a => a -> Unique
getUnique Name
nm, TyVar
tv)
                       | ATyVar Name
nm TyVar
tv <- NameEnv TcTyThing -> [TcTyThing]
forall a. NameEnv a -> [a]
nameEnvElts (TcLclEnv -> NameEnv TcTyThing
tcl_env TcLclEnv
env) ]
           subst :: TCvSubst
subst = InScopeSet -> TvSubstEnv -> TCvSubst
mkTvSubst
                     (VarSet -> InScopeSet
mkInScopeSet (VarSet -> InScopeSet) -> VarSet -> InScopeSet
forall a b. (a -> b) -> a -> b
$ [TyVar] -> VarSet
mkVarSet ([TyVar] -> VarSet) -> [TyVar] -> VarSet
forall a b. (a -> b) -> a -> b
$ ((Unique, TyVar) -> TyVar) -> [(Unique, TyVar)] -> [TyVar]
forall a b. (a -> b) -> [a] -> [b]
map (Unique, TyVar) -> TyVar
forall a b. (a, b) -> b
snd [(Unique, TyVar)]
subst_prs)
                     ([(Unique, Type)] -> TvSubstEnv
forall elt key. [(Unique, elt)] -> UniqFM key elt
listToUFM_Directly ([(Unique, Type)] -> TvSubstEnv) -> [(Unique, Type)] -> TvSubstEnv
forall a b. (a -> b) -> a -> b
$ ((Unique, TyVar) -> (Unique, Type))
-> [(Unique, TyVar)] -> [(Unique, Type)]
forall a b. (a -> b) -> [a] -> [b]
map ((TyVar -> Type) -> (Unique, TyVar) -> (Unique, Type)
forall a b c. (a -> b) -> (c, a) -> (c, b)
liftSnd TyVar -> Type
mkTyVarTy) [(Unique, TyVar)]
subst_prs)
           ty' :: Type
ty' = HasCallStack => TCvSubst -> Type -> Type
TCvSubst -> Type -> Type
substTy TCvSubst
subst Type
XXType GhcRn
ty
       (Type, Type) -> TcM (Type, Type)
forall (m :: * -> *) a. Monad m => a -> m a
return (Type
ty', HasDebugCallStack => Type -> Type
Type -> Type
tcTypeKind Type
ty')

tc_infer_hs_type TcTyMode
_ (HsExplicitListTy XExplicitListTy GhcRn
_ PromotionFlag
_ [LHsType GhcRn]
tys)
  | [GenLocated SrcSpanAnnA (HsType GhcRn)] -> Bool
forall (t :: * -> *) a. Foldable t => t a -> Bool
null [GenLocated SrcSpanAnnA (HsType GhcRn)]
[LHsType GhcRn]
tys  -- this is so that we can use visible kind application with '[]
              -- e.g ... '[] @Bool
  = (Type, Type) -> TcM (Type, Type)
forall (m :: * -> *) a. Monad m => a -> m a
return (TyCon -> Type
mkTyConTy TyCon
promotedNilDataCon,
            [TyVar] -> Type -> Type
mkSpecForAllTys [TyVar
alphaTyVar] (Type -> Type) -> Type -> Type
forall a b. (a -> b) -> a -> b
$ Type -> Type
mkListTy Type
alphaTy)

tc_infer_hs_type TcTyMode
mode HsType GhcRn
other_ty
  = do { Type
kv <- TcM Type
newMetaKindVar
       ; Type
ty' <- TcTyMode -> HsType GhcRn -> Type -> TcM Type
tc_hs_type TcTyMode
mode HsType GhcRn
other_ty Type
kv
       ; (Type, Type) -> TcM (Type, Type)
forall (m :: * -> *) a. Monad m => a -> m a
return (Type
ty', Type
kv) }

{-
Note [Typechecking HsCoreTys]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
HsCoreTy is an escape hatch that allows embedding Core Types in HsTypes.
As such, there's not much to be done in order to typecheck an HsCoreTy,
since it's already been typechecked to some extent. There is one thing that
we must do, however: we must substitute the type variables from the tcl_env.
To see why, consider GeneralizedNewtypeDeriving, which is one of the main
clients of HsCoreTy (example adapted from #14579):

  newtype T a = MkT a deriving newtype Eq

This will produce an InstInfo GhcPs that looks roughly like this:

  instance forall a_1. Eq a_1 => Eq (T a_1) where
    (==) = coerce @(  a_1 ->   a_1 -> Bool) -- The type within @(...) is an HsCoreTy
                  @(T a_1 -> T a_1 -> Bool) -- So is this
                  (==)

This is then fed into the renamer. Since all of the type variables in this
InstInfo use Exact RdrNames, the resulting InstInfo GhcRn looks basically
identical. Things get more interesting when the InstInfo is fed into the
typechecker, however. GHC will first generate fresh skolems to instantiate
the instance-bound type variables with. In the example above, we might generate
the skolem a_2 and use that to instantiate a_1, which extends the local type
environment (tcl_env) with [a_1 :-> a_2]. This gives us:

  instance forall a_2. Eq a_2 => Eq (T a_2) where ...

To ensure that the body of this instance is well scoped, every occurrence of
the `a` type variable should refer to a_2, the new skolem. However, the
HsCoreTys mention a_1, not a_2. Luckily, the tcl_env provides exactly the
substitution we need ([a_1 :-> a_2]) to fix up the scoping. We apply this
substitution to each HsCoreTy and all is well:

  instance forall a_2. Eq a_2 => Eq (T a_2) where
    (==) = coerce @(  a_2 ->   a_2 -> Bool)
                  @(T a_2 -> T a_2 -> Bool)
                  (==)
-}

------------------------------------------
tcLHsType :: LHsType GhcRn -> TcKind -> TcM TcType
tcLHsType :: LHsType GhcRn -> Type -> TcM Type
tcLHsType LHsType GhcRn
hs_ty Type
exp_kind
  = TcTyMode -> LHsType GhcRn -> Type -> TcM Type
tc_lhs_type TcTyMode
typeLevelMode LHsType GhcRn
hs_ty Type
exp_kind

tc_lhs_type :: TcTyMode -> LHsType GhcRn -> TcKind -> TcM TcType
tc_lhs_type :: TcTyMode -> LHsType GhcRn -> Type -> TcM Type
tc_lhs_type TcTyMode
mode (L SrcSpanAnnA
span HsType GhcRn
ty) Type
exp_kind
  = SrcSpanAnnA -> TcM Type -> TcM Type
forall ann a. SrcSpanAnn' ann -> TcRn a -> TcRn a
setSrcSpanA SrcSpanAnnA
span (TcM Type -> TcM Type) -> TcM Type -> TcM Type
forall a b. (a -> b) -> a -> b
$
    TcTyMode -> HsType GhcRn -> Type -> TcM Type
tc_hs_type TcTyMode
mode HsType GhcRn
ty Type
exp_kind

tc_hs_type :: TcTyMode -> HsType GhcRn -> TcKind -> TcM TcType
-- See Note [Bidirectional type checking]

tc_hs_type :: TcTyMode -> HsType GhcRn -> Type -> TcM Type
tc_hs_type TcTyMode
mode (HsParTy XParTy GhcRn
_ LHsType GhcRn
ty)   Type
exp_kind = TcTyMode -> LHsType GhcRn -> Type -> TcM Type
tc_lhs_type TcTyMode
mode LHsType GhcRn
ty Type
exp_kind
tc_hs_type TcTyMode
mode (HsDocTy XDocTy GhcRn
_ LHsType GhcRn
ty LHsDocString
_) Type
exp_kind = TcTyMode -> LHsType GhcRn -> Type -> TcM Type
tc_lhs_type TcTyMode
mode LHsType GhcRn
ty Type
exp_kind
tc_hs_type TcTyMode
_ ty :: HsType GhcRn
ty@(HsBangTy XBangTy GhcRn
_ HsSrcBang
bang LHsType GhcRn
_) Type
_
    -- While top-level bangs at this point are eliminated (eg !(Maybe Int)),
    -- other kinds of bangs are not (eg ((!Maybe) Int)). These kinds of
    -- bangs are invalid, so fail. (#7210, #14761)
    = do { let bangError :: String -> TcM Type
bangError String
err = SDoc -> TcM Type
forall a. SDoc -> TcM a
failWith (SDoc -> TcM Type) -> SDoc -> TcM Type
forall a b. (a -> b) -> a -> b
$
                 String -> SDoc
text String
"Unexpected" SDoc -> SDoc -> SDoc
<+> String -> SDoc
text String
err SDoc -> SDoc -> SDoc
<+> String -> SDoc
text String
"annotation:" SDoc -> SDoc -> SDoc
<+> HsType GhcRn -> SDoc
forall a. Outputable a => a -> SDoc
ppr HsType GhcRn
ty SDoc -> SDoc -> SDoc
$$
                 String -> SDoc
text String
err SDoc -> SDoc -> SDoc
<+> String -> SDoc
text String
"annotation cannot appear nested inside a type"
         ; case HsSrcBang
bang of
             HsSrcBang SourceText
_ SrcUnpackedness
SrcUnpack SrcStrictness
_           -> String -> TcM Type
bangError String
"UNPACK"
             HsSrcBang SourceText
_ SrcUnpackedness
SrcNoUnpack SrcStrictness
_         -> String -> TcM Type
bangError String
"NOUNPACK"
             HsSrcBang SourceText
_ SrcUnpackedness
NoSrcUnpack SrcStrictness
SrcLazy   -> String -> TcM Type
bangError String
"laziness"
             HsSrcBang SourceText
_ SrcUnpackedness
_ SrcStrictness
_                   -> String -> TcM Type
bangError String
"strictness" }
tc_hs_type TcTyMode
_ ty :: HsType GhcRn
ty@(HsRecTy {})      Type
_
      -- Record types (which only show up temporarily in constructor
      -- signatures) should have been removed by now
    = SDoc -> TcM Type
forall a. SDoc -> TcM a
failWithTc (String -> SDoc
text String
"Record syntax is illegal here:" SDoc -> SDoc -> SDoc
<+> HsType GhcRn -> SDoc
forall a. Outputable a => a -> SDoc
ppr HsType GhcRn
ty)

-- HsSpliced is an annotation produced by 'GHC.Rename.Splice.rnSpliceType'.
-- Here we get rid of it and add the finalizers to the global environment
-- while capturing the local environment.
--
-- See Note [Delaying modFinalizers in untyped splices].
tc_hs_type TcTyMode
mode (HsSpliceTy XSpliceTy GhcRn
_ (HsSpliced XSpliced GhcRn
_ ThModFinalizers
mod_finalizers (HsSplicedTy HsType GhcRn
ty)))
           Type
exp_kind
  = do ThModFinalizers -> TcM ()
addModFinalizersWithLclEnv ThModFinalizers
mod_finalizers
       TcTyMode -> HsType GhcRn -> Type -> TcM Type
tc_hs_type TcTyMode
mode HsType GhcRn
ty Type
exp_kind

-- This should never happen; type splices are expanded by the renamer
tc_hs_type TcTyMode
_ ty :: HsType GhcRn
ty@(HsSpliceTy {}) Type
_exp_kind
  = SDoc -> TcM Type
forall a. SDoc -> TcM a
failWithTc (String -> SDoc
text String
"Unexpected type splice:" SDoc -> SDoc -> SDoc
<+> HsType GhcRn -> SDoc
forall a. Outputable a => a -> SDoc
ppr HsType GhcRn
ty)

---------- Functions and applications
tc_hs_type TcTyMode
mode (HsFunTy XFunTy GhcRn
_ HsArrow GhcRn
mult LHsType GhcRn
ty1 LHsType GhcRn
ty2) Type
exp_kind
  = TcTyMode
-> HsArrow GhcRn
-> LHsType GhcRn
-> LHsType GhcRn
-> Type
-> TcM Type
tc_fun_type TcTyMode
mode HsArrow GhcRn
mult LHsType GhcRn
ty1 LHsType GhcRn
ty2 Type
exp_kind

tc_hs_type TcTyMode
mode (HsOpTy XOpTy GhcRn
_ LHsType GhcRn
ty1 (L SrcSpanAnnN
_ Name
op) LHsType GhcRn
ty2) Type
exp_kind
  | Name
op Name -> Unique -> Bool
forall a. Uniquable a => a -> Unique -> Bool
`hasKey` Unique
funTyConKey
  = TcTyMode
-> HsArrow GhcRn
-> LHsType GhcRn
-> LHsType GhcRn
-> Type
-> TcM Type
tc_fun_type TcTyMode
mode (IsUnicodeSyntax -> HsArrow GhcRn
forall pass. IsUnicodeSyntax -> HsArrow pass
HsUnrestrictedArrow IsUnicodeSyntax
NormalSyntax) LHsType GhcRn
ty1 LHsType GhcRn
ty2 Type
exp_kind

--------- Foralls
tc_hs_type TcTyMode
mode (HsForAllTy { hst_tele :: forall pass. HsType pass -> HsForAllTelescope pass
hst_tele = HsForAllTelescope GhcRn
tele, hst_body :: forall pass. HsType pass -> LHsType pass
hst_body = LHsType GhcRn
ty }) Type
exp_kind
  = do { ([TcTyVarBinder]
tv_bndrs, Type
ty') <- TcTyMode
-> HsForAllTelescope GhcRn
-> TcM Type
-> TcM ([TcTyVarBinder], Type)
forall a.
TcTyMode
-> HsForAllTelescope GhcRn -> TcM a -> TcM ([TcTyVarBinder], a)
tcTKTelescope TcTyMode
mode HsForAllTelescope GhcRn
tele (TcM Type -> TcM ([TcTyVarBinder], Type))
-> TcM Type -> TcM ([TcTyVarBinder], Type)
forall a b. (a -> b) -> a -> b
$
                            TcTyMode -> LHsType GhcRn -> Type -> TcM Type
tc_lhs_type TcTyMode
mode LHsType GhcRn
ty Type
exp_kind
                 -- Pass on the mode from the type, to any wildcards
                 -- in kind signatures on the forall'd variables
                 -- e.g.      f :: _ -> Int -> forall (a :: _). blah
                 -- Why exp_kind?  See Note [Body kind of HsForAllTy]

       -- Do not kind-generalise here!  See Note [Kind generalisation]

       ; Type -> TcM Type
forall (m :: * -> *) a. Monad m => a -> m a
return ([TcTyVarBinder] -> Type -> Type
mkForAllTys [TcTyVarBinder]
tv_bndrs Type
ty') }

tc_hs_type TcTyMode
mode (HsQualTy { hst_ctxt :: forall pass. HsType pass -> Maybe (LHsContext pass)
hst_ctxt = Maybe (LHsContext GhcRn)
ctxt, hst_body :: forall pass. HsType pass -> LHsType pass
hst_body = LHsType GhcRn
rn_ty }) Type
exp_kind
  | [GenLocated SrcSpanAnnA (HsType GhcRn)] -> Bool
forall (t :: * -> *) a. Foldable t => t a -> Bool
null (Maybe (LHsContext GhcRn) -> [LHsType GhcRn]
forall (p :: Pass).
Maybe (LHsContext (GhcPass p)) -> HsContext (GhcPass p)
fromMaybeContext Maybe (LHsContext GhcRn)
ctxt)
  = TcTyMode -> LHsType GhcRn -> Type -> TcM Type
tc_lhs_type TcTyMode
mode LHsType GhcRn
rn_ty Type
exp_kind

  -- See Note [Body kind of a HsQualTy]
  | Type -> Bool
tcIsConstraintKind Type
exp_kind
  = do { [Type]
ctxt' <- TcTyMode -> Maybe (LHsContext GhcRn) -> TcM [Type]
tc_hs_context TcTyMode
mode Maybe (LHsContext GhcRn)
ctxt
       ; Type
ty'   <- TcTyMode -> LHsType GhcRn -> Type -> TcM Type
tc_lhs_type TcTyMode
mode LHsType GhcRn
rn_ty Type
constraintKind
       ; Type -> TcM Type
forall (m :: * -> *) a. Monad m => a -> m a
return ([Type] -> Type -> Type
mkPhiTy [Type]
ctxt' Type
ty') }

  | Bool
otherwise
  = do { [Type]
ctxt' <- TcTyMode -> Maybe (LHsContext GhcRn) -> TcM [Type]
tc_hs_context TcTyMode
mode Maybe (LHsContext GhcRn)
ctxt

       ; Type
ek <- TcM Type
newOpenTypeKind  -- The body kind (result of the function) can
                                -- be TYPE r, for any r, hence newOpenTypeKind
       ; Type
ty' <- TcTyMode -> LHsType GhcRn -> Type -> TcM Type
tc_lhs_type TcTyMode
mode LHsType GhcRn
rn_ty Type
ek
       ; HasDebugCallStack =>
HsType GhcRn -> Type -> Type -> Type -> TcM Type
HsType GhcRn -> Type -> Type -> Type -> TcM Type
checkExpectedKind (GenLocated SrcSpanAnnA (HsType GhcRn) -> HsType GhcRn
forall l e. GenLocated l e -> e
unLoc GenLocated SrcSpanAnnA (HsType GhcRn)
LHsType GhcRn
rn_ty) ([Type] -> Type -> Type
mkPhiTy [Type]
ctxt' Type
ty')
                           Type
liftedTypeKind Type
exp_kind }

--------- Lists, arrays, and tuples
tc_hs_type TcTyMode
mode rn_ty :: HsType GhcRn
rn_ty@(HsListTy XListTy GhcRn
_ LHsType GhcRn
elt_ty) Type
exp_kind
  = do { Type
tau_ty <- TcTyMode -> LHsType GhcRn -> Type -> TcM Type
tc_lhs_type TcTyMode
mode LHsType GhcRn
elt_ty Type
liftedTypeKind
       ; TyCon -> TcM ()
checkWiredInTyCon TyCon
listTyCon
       ; HasDebugCallStack =>
HsType GhcRn -> Type -> Type -> Type -> TcM Type
HsType GhcRn -> Type -> Type -> Type -> TcM Type
checkExpectedKind HsType GhcRn
rn_ty (Type -> Type
mkListTy Type
tau_ty) Type
liftedTypeKind Type
exp_kind }

-- See Note [Distinguishing tuple kinds] in GHC.Hs.Type
-- See Note [Inferring tuple kinds]
tc_hs_type TcTyMode
mode rn_ty :: HsType GhcRn
rn_ty@(HsTupleTy XTupleTy GhcRn
_ HsTupleSort
HsBoxedOrConstraintTuple [LHsType GhcRn]
hs_tys) Type
exp_kind
     -- (NB: not zonking before looking at exp_k, to avoid left-right bias)
  | Just TupleSort
tup_sort <- Type -> Maybe TupleSort
tupKindSort_maybe Type
exp_kind
  = String -> SDoc -> TcM ()
traceTc String
"tc_hs_type tuple" ([GenLocated SrcSpanAnnA (HsType GhcRn)] -> SDoc
forall a. Outputable a => a -> SDoc
ppr [GenLocated SrcSpanAnnA (HsType GhcRn)]
[LHsType GhcRn]
hs_tys) TcM () -> TcM Type -> TcM Type
forall (m :: * -> *) a b. Monad m => m a -> m b -> m b
>>
    HsType GhcRn
-> TcTyMode -> TupleSort -> [LHsType GhcRn] -> Type -> TcM Type
tc_tuple HsType GhcRn
rn_ty TcTyMode
mode TupleSort
tup_sort [LHsType GhcRn]
hs_tys Type
exp_kind
  | Bool
otherwise
  = do { String -> SDoc -> TcM ()
traceTc String
"tc_hs_type tuple 2" ([GenLocated SrcSpanAnnA (HsType GhcRn)] -> SDoc
forall a. Outputable a => a -> SDoc
ppr [GenLocated SrcSpanAnnA (HsType GhcRn)]
[LHsType GhcRn]
hs_tys)
       ; ([Type]
tys, [Type]
kinds) <- (GenLocated SrcSpanAnnA (HsType GhcRn) -> TcM (Type, Type))
-> [GenLocated SrcSpanAnnA (HsType GhcRn)]
-> IOEnv (Env TcGblEnv TcLclEnv) ([Type], [Type])
forall (m :: * -> *) a b c.
Applicative m =>
(a -> m (b, c)) -> [a] -> m ([b], [c])
mapAndUnzipM (TcTyMode -> LHsType GhcRn -> TcM (Type, Type)
tc_infer_lhs_type TcTyMode
mode) [GenLocated SrcSpanAnnA (HsType GhcRn)]
[LHsType GhcRn]
hs_tys
       ; [Type]
kinds <- (Type -> TcM Type) -> [Type] -> TcM [Type]
forall (t :: * -> *) (m :: * -> *) a b.
(Traversable t, Monad m) =>
(a -> m b) -> t a -> m (t b)
mapM Type -> TcM Type
zonkTcType [Type]
kinds
           -- Infer each arg type separately, because errors can be
           -- confusing if we give them a shared kind.  Eg #7410
           -- (Either Int, Int), we do not want to get an error saying
           -- "the second argument of a tuple should have kind *->*"

       ; let (Type
arg_kind, TupleSort
tup_sort)
               = case [ (Type
k,TupleSort
s) | Type
k <- [Type]
kinds
                              , Just TupleSort
s <- [Type -> Maybe TupleSort
tupKindSort_maybe Type
k] ] of
                    ((Type
k,TupleSort
s) : [(Type, TupleSort)]
_) -> (Type
k,TupleSort
s)
                    [] -> (Type
liftedTypeKind, TupleSort
BoxedTuple)
         -- In the [] case, it's not clear what the kind is, so guess *

       ; [Type]
tys' <- [TcM Type] -> TcM [Type]
forall (t :: * -> *) (m :: * -> *) a.
(Traversable t, Monad m) =>
t (m a) -> m (t a)
sequence [ SrcSpanAnnA -> TcM Type -> TcM Type
forall ann a. SrcSpanAnn' ann -> TcRn a -> TcRn a
setSrcSpanA SrcSpanAnnA
loc (TcM Type -> TcM Type) -> TcM Type -> TcM Type
forall a b. (a -> b) -> a -> b
$
                            HasDebugCallStack =>
HsType GhcRn -> Type -> Type -> Type -> TcM Type
HsType GhcRn -> Type -> Type -> Type -> TcM Type
checkExpectedKind HsType GhcRn
hs_ty Type
ty Type
kind Type
arg_kind
                          | ((L SrcSpanAnnA
loc HsType GhcRn
hs_ty),Type
ty,Type
kind) <- [GenLocated SrcSpanAnnA (HsType GhcRn)]
-> [Type]
-> [Type]
-> [(GenLocated SrcSpanAnnA (HsType GhcRn), Type, Type)]
forall a b c. [a] -> [b] -> [c] -> [(a, b, c)]
zip3 [GenLocated SrcSpanAnnA (HsType GhcRn)]
[LHsType GhcRn]
hs_tys [Type]
tys [Type]
kinds ]

       ; HsType GhcRn -> TupleSort -> [Type] -> [Type] -> Type -> TcM Type
finish_tuple HsType GhcRn
rn_ty TupleSort
tup_sort [Type]
tys' ((Type -> Type) -> [Type] -> [Type]
forall a b. (a -> b) -> [a] -> [b]
map (Type -> Type -> Type
forall a b. a -> b -> a
const Type
arg_kind) [Type]
tys') Type
exp_kind }


tc_hs_type TcTyMode
mode rn_ty :: HsType GhcRn
rn_ty@(HsTupleTy XTupleTy GhcRn
_ HsTupleSort
HsUnboxedTuple [LHsType GhcRn]
tys) Type
exp_kind
  = HsType GhcRn
-> TcTyMode -> TupleSort -> [LHsType GhcRn] -> Type -> TcM Type
tc_tuple HsType GhcRn
rn_ty TcTyMode
mode TupleSort
UnboxedTuple [LHsType GhcRn]
tys Type
exp_kind

tc_hs_type TcTyMode
mode rn_ty :: HsType GhcRn
rn_ty@(HsSumTy XSumTy GhcRn
_ [LHsType GhcRn]
hs_tys) Type
exp_kind
  = do { let arity :: Arity
arity = [GenLocated SrcSpanAnnA (HsType GhcRn)] -> Arity
forall (t :: * -> *) a. Foldable t => t a -> Arity
length [GenLocated SrcSpanAnnA (HsType GhcRn)]
[LHsType GhcRn]
hs_tys
       ; [Type]
arg_kinds <- (GenLocated SrcSpanAnnA (HsType GhcRn) -> TcM Type)
-> [GenLocated SrcSpanAnnA (HsType GhcRn)] -> TcM [Type]
forall (t :: * -> *) (m :: * -> *) a b.
(Traversable t, Monad m) =>
(a -> m b) -> t a -> m (t b)
mapM (\GenLocated SrcSpanAnnA (HsType GhcRn)
_ -> TcM Type
newOpenTypeKind) [GenLocated SrcSpanAnnA (HsType GhcRn)]
[LHsType GhcRn]
hs_tys
       ; [Type]
tau_tys   <- (GenLocated SrcSpanAnnA (HsType GhcRn) -> Type -> TcM Type)
-> [GenLocated SrcSpanAnnA (HsType GhcRn)] -> [Type] -> TcM [Type]
forall (m :: * -> *) a b c.
Applicative m =>
(a -> b -> m c) -> [a] -> [b] -> m [c]
zipWithM (TcTyMode -> LHsType GhcRn -> Type -> TcM Type
tc_lhs_type TcTyMode
mode) [GenLocated SrcSpanAnnA (HsType GhcRn)]
[LHsType GhcRn]
hs_tys [Type]
arg_kinds
       ; let arg_reps :: [Type]
arg_reps = (Type -> Type) -> [Type] -> [Type]
forall a b. (a -> b) -> [a] -> [b]
map HasDebugCallStack => Type -> Type
Type -> Type
kindRep [Type]
arg_kinds
             arg_tys :: [Type]
arg_tys  = [Type]
arg_reps [Type] -> [Type] -> [Type]
forall a. [a] -> [a] -> [a]
++ [Type]
tau_tys
             sum_ty :: Type
sum_ty   = TyCon -> [Type] -> Type
mkTyConApp (Arity -> TyCon
sumTyCon Arity
arity) [Type]
arg_tys
             sum_kind :: Type
sum_kind = [Type] -> Type
unboxedSumKind [Type]
arg_reps
       ; HasDebugCallStack =>
HsType GhcRn -> Type -> Type -> Type -> TcM Type
HsType GhcRn -> Type -> Type -> Type -> TcM Type
checkExpectedKind HsType GhcRn
rn_ty Type
sum_ty Type
sum_kind Type
exp_kind
       }

--------- Promoted lists and tuples
tc_hs_type TcTyMode
mode rn_ty :: HsType GhcRn
rn_ty@(HsExplicitListTy XExplicitListTy GhcRn
_ PromotionFlag
_ [LHsType GhcRn]
tys) Type
exp_kind
  = do { [(Type, Type)]
tks <- (GenLocated SrcSpanAnnA (HsType GhcRn) -> TcM (Type, Type))
-> [GenLocated SrcSpanAnnA (HsType GhcRn)]
-> IOEnv (Env TcGblEnv TcLclEnv) [(Type, Type)]
forall (t :: * -> *) (m :: * -> *) a b.
(Traversable t, Monad m) =>
(a -> m b) -> t a -> m (t b)
mapM (TcTyMode -> LHsType GhcRn -> TcM (Type, Type)
tc_infer_lhs_type TcTyMode
mode) [GenLocated SrcSpanAnnA (HsType GhcRn)]
[LHsType GhcRn]
tys
       ; ([Type]
taus', Type
kind) <- [LHsType GhcRn] -> [(Type, Type)] -> TcM ([Type], Type)
unifyKinds [LHsType GhcRn]
tys [(Type, Type)]
tks
       ; let ty :: Type
ty = ((Type -> Type -> Type) -> Type -> [Type] -> Type
forall (t :: * -> *) a b.
Foldable t =>
(a -> b -> b) -> b -> t a -> b
foldr (Type -> Type -> Type -> Type
mk_cons Type
kind) (Type -> Type
mk_nil Type
kind) [Type]
taus')
       ; HasDebugCallStack =>
HsType GhcRn -> Type -> Type -> Type -> TcM Type
HsType GhcRn -> Type -> Type -> Type -> TcM Type
checkExpectedKind HsType GhcRn
rn_ty Type
ty (Type -> Type
mkListTy Type
kind) Type
exp_kind }
  where
    mk_cons :: Type -> Type -> Type -> Type
mk_cons Type
k Type
a Type
b = TyCon -> [Type] -> Type
mkTyConApp (DataCon -> TyCon
promoteDataCon DataCon
consDataCon) [Type
k, Type
a, Type
b]
    mk_nil :: Type -> Type
mk_nil  Type
k     = TyCon -> [Type] -> Type
mkTyConApp (DataCon -> TyCon
promoteDataCon DataCon
nilDataCon) [Type
k]

tc_hs_type TcTyMode
mode rn_ty :: HsType GhcRn
rn_ty@(HsExplicitTupleTy XExplicitTupleTy GhcRn
_ [LHsType GhcRn]
tys) Type
exp_kind
  -- using newMetaKindVar means that we force instantiations of any polykinded
  -- types. At first, I just used tc_infer_lhs_type, but that led to #11255.
  = do { [Type]
ks   <- Arity -> TcM Type -> TcM [Type]
forall (m :: * -> *) a. Applicative m => Arity -> m a -> m [a]
replicateM Arity
arity TcM Type
newMetaKindVar
       ; [Type]
taus <- (GenLocated SrcSpanAnnA (HsType GhcRn) -> Type -> TcM Type)
-> [GenLocated SrcSpanAnnA (HsType GhcRn)] -> [Type] -> TcM [Type]
forall (m :: * -> *) a b c.
Applicative m =>
(a -> b -> m c) -> [a] -> [b] -> m [c]
zipWithM (TcTyMode -> LHsType GhcRn -> Type -> TcM Type
tc_lhs_type TcTyMode
mode) [GenLocated SrcSpanAnnA (HsType GhcRn)]
[LHsType GhcRn]
tys [Type]
ks
       ; let kind_con :: TyCon
kind_con   = Boxity -> Arity -> TyCon
tupleTyCon           Boxity
Boxed Arity
arity
             ty_con :: TyCon
ty_con     = Boxity -> Arity -> TyCon
promotedTupleDataCon Boxity
Boxed Arity
arity
             tup_k :: Type
tup_k      = TyCon -> [Type] -> Type
mkTyConApp TyCon
kind_con [Type]
ks
       ; Arity -> TcM ()
checkTupSize Arity
arity
       ; HasDebugCallStack =>
HsType GhcRn -> Type -> Type -> Type -> TcM Type
HsType GhcRn -> Type -> Type -> Type -> TcM Type
checkExpectedKind HsType GhcRn
rn_ty (TyCon -> [Type] -> Type
mkTyConApp TyCon
ty_con ([Type]
ks [Type] -> [Type] -> [Type]
forall a. [a] -> [a] -> [a]
++ [Type]
taus)) Type
tup_k Type
exp_kind }
  where
    arity :: Arity
arity = [GenLocated SrcSpanAnnA (HsType GhcRn)] -> Arity
forall (t :: * -> *) a. Foldable t => t a -> Arity
length [GenLocated SrcSpanAnnA (HsType GhcRn)]
[LHsType GhcRn]
tys

--------- Constraint types
tc_hs_type TcTyMode
mode rn_ty :: HsType GhcRn
rn_ty@(HsIParamTy XIParamTy GhcRn
_ (L SrcSpan
_ HsIPName
n) LHsType GhcRn
ty) Type
exp_kind
  = do { MASSERT( isTypeLevel (mode_tyki mode) )
       ; Type
ty' <- TcTyMode -> LHsType GhcRn -> Type -> TcM Type
tc_lhs_type TcTyMode
mode LHsType GhcRn
ty Type
liftedTypeKind
       ; let n' :: Type
n' = FastString -> Type
mkStrLitTy (FastString -> Type) -> FastString -> Type
forall a b. (a -> b) -> a -> b
$ HsIPName -> FastString
hsIPNameFS HsIPName
n
       ; Class
ipClass <- Name -> TcM Class
tcLookupClass Name
ipClassName
       ; HasDebugCallStack =>
HsType GhcRn -> Type -> Type -> Type -> TcM Type
HsType GhcRn -> Type -> Type -> Type -> TcM Type
checkExpectedKind HsType GhcRn
rn_ty (Class -> [Type] -> Type
mkClassPred Class
ipClass [Type
n',Type
ty'])
                           Type
constraintKind Type
exp_kind }

tc_hs_type TcTyMode
_ rn_ty :: HsType GhcRn
rn_ty@(HsStarTy XStarTy GhcRn
_ Bool
_) Type
exp_kind
  -- Desugaring 'HsStarTy' to 'Data.Kind.Type' here means that we don't have to
  -- handle it in 'coreView' and 'tcView'.
  = HasDebugCallStack =>
HsType GhcRn -> Type -> Type -> Type -> TcM Type
HsType GhcRn -> Type -> Type -> Type -> TcM Type
checkExpectedKind HsType GhcRn
rn_ty Type
liftedTypeKind Type
liftedTypeKind Type
exp_kind

--------- Literals
tc_hs_type TcTyMode
_ rn_ty :: HsType GhcRn
rn_ty@(HsTyLit XTyLit GhcRn
_ (HsNumTy SourceText
_ Integer
n)) Type
exp_kind
  = do { TyCon -> TcM ()
checkWiredInTyCon TyCon
naturalTyCon
       ; HasDebugCallStack =>
HsType GhcRn -> Type -> Type -> Type -> TcM Type
HsType GhcRn -> Type -> Type -> Type -> TcM Type
checkExpectedKind HsType GhcRn
rn_ty (Integer -> Type
mkNumLitTy Integer
n) Type
naturalTy Type
exp_kind }

tc_hs_type TcTyMode
_ rn_ty :: HsType GhcRn
rn_ty@(HsTyLit XTyLit GhcRn
_ (HsStrTy SourceText
_ FastString
s)) Type
exp_kind
  = do { TyCon -> TcM ()
checkWiredInTyCon TyCon
typeSymbolKindCon
       ; HasDebugCallStack =>
HsType GhcRn -> Type -> Type -> Type -> TcM Type
HsType GhcRn -> Type -> Type -> Type -> TcM Type
checkExpectedKind HsType GhcRn
rn_ty (FastString -> Type
mkStrLitTy FastString
s) Type
typeSymbolKind Type
exp_kind }
tc_hs_type TcTyMode
_ rn_ty :: HsType GhcRn
rn_ty@(HsTyLit XTyLit GhcRn
_ (HsCharTy SourceText
_ Char
c)) Type
exp_kind
  = do { TyCon -> TcM ()
checkWiredInTyCon TyCon
charTyCon
       ; HasDebugCallStack =>
HsType GhcRn -> Type -> Type -> Type -> TcM Type
HsType GhcRn -> Type -> Type -> Type -> TcM Type
checkExpectedKind HsType GhcRn
rn_ty (Char -> Type
mkCharLitTy Char
c) Type
charTy Type
exp_kind }

--------- Wildcards

tc_hs_type TcTyMode
mode ty :: HsType GhcRn
ty@(HsWildCardTy XWildCardTy GhcRn
_)        Type
ek
  = IsExtraConstraint -> TcTyMode -> HsType GhcRn -> Type -> TcM Type
tcAnonWildCardOcc IsExtraConstraint
NoExtraConstraint TcTyMode
mode HsType GhcRn
ty Type
ek

--------- Potentially kind-polymorphic types: call the "up" checker
-- See Note [Future-proofing the type checker]
tc_hs_type TcTyMode
mode ty :: HsType GhcRn
ty@(HsTyVar {})            Type
ek = HasDebugCallStack => TcTyMode -> HsType GhcRn -> Type -> TcM Type
TcTyMode -> HsType GhcRn -> Type -> TcM Type
tc_infer_hs_type_ek TcTyMode
mode HsType GhcRn
ty Type
ek
tc_hs_type TcTyMode
mode ty :: HsType GhcRn
ty@(HsAppTy {})            Type
ek = HasDebugCallStack => TcTyMode -> HsType GhcRn -> Type -> TcM Type
TcTyMode -> HsType GhcRn -> Type -> TcM Type
tc_infer_hs_type_ek TcTyMode
mode HsType GhcRn
ty Type
ek
tc_hs_type TcTyMode
mode ty :: HsType GhcRn
ty@(HsAppKindTy{})         Type
ek = HasDebugCallStack => TcTyMode -> HsType GhcRn -> Type -> TcM Type
TcTyMode -> HsType GhcRn -> Type -> TcM Type
tc_infer_hs_type_ek TcTyMode
mode HsType GhcRn
ty Type
ek
tc_hs_type TcTyMode
mode ty :: HsType GhcRn
ty@(HsOpTy {})             Type
ek = HasDebugCallStack => TcTyMode -> HsType GhcRn -> Type -> TcM Type
TcTyMode -> HsType GhcRn -> Type -> TcM Type
tc_infer_hs_type_ek TcTyMode
mode HsType GhcRn
ty Type
ek
tc_hs_type TcTyMode
mode ty :: HsType GhcRn
ty@(HsKindSig {})          Type
ek = HasDebugCallStack => TcTyMode -> HsType GhcRn -> Type -> TcM Type
TcTyMode -> HsType GhcRn -> Type -> TcM Type
tc_infer_hs_type_ek TcTyMode
mode HsType GhcRn
ty Type
ek
tc_hs_type TcTyMode
mode ty :: HsType GhcRn
ty@(XHsType {})            Type
ek = HasDebugCallStack => TcTyMode -> HsType GhcRn -> Type -> TcM Type
TcTyMode -> HsType GhcRn -> Type -> TcM Type
tc_infer_hs_type_ek TcTyMode
mode HsType GhcRn
ty Type
ek

{-
Note [Variable Specificity and Forall Visibility]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
A HsForAllTy contains an HsForAllTelescope to denote the visibility of the forall
binder. Furthermore, each invisible type variable binder also has a
Specificity. Together, these determine the variable binders (ArgFlag) for each
variable in the generated ForAllTy type.

This table summarises this relation:
----------------------------------------------------------------------------
| User-written type         HsForAllTelescope   Specificity        ArgFlag
|---------------------------------------------------------------------------
| f :: forall a. type       HsForAllInvis       SpecifiedSpec      Specified
| f :: forall {a}. type     HsForAllInvis       InferredSpec       Inferred
| f :: forall a -> type     HsForAllVis         SpecifiedSpec      Required
| f :: forall {a} -> type   HsForAllVis         InferredSpec       /
|   This last form is non-sensical and is thus rejected.
----------------------------------------------------------------------------

For more information regarding the interpretation of the resulting ArgFlag, see
Note [VarBndrs, TyCoVarBinders, TyConBinders, and visibility] in "GHC.Core.TyCo.Rep".
-}

------------------------------------------
tc_mult :: TcTyMode -> HsArrow GhcRn -> TcM Mult
tc_mult :: TcTyMode -> HsArrow GhcRn -> TcM Type
tc_mult TcTyMode
mode HsArrow GhcRn
ty = TcTyMode -> LHsType GhcRn -> Type -> TcM Type
tc_lhs_type TcTyMode
mode (HsArrow GhcRn -> LHsType GhcRn
arrowToHsType HsArrow GhcRn
ty) Type
multiplicityTy
------------------------------------------
tc_fun_type :: TcTyMode -> HsArrow GhcRn -> LHsType GhcRn -> LHsType GhcRn -> TcKind
            -> TcM TcType
tc_fun_type :: TcTyMode
-> HsArrow GhcRn
-> LHsType GhcRn
-> LHsType GhcRn
-> Type
-> TcM Type
tc_fun_type TcTyMode
mode HsArrow GhcRn
mult LHsType GhcRn
ty1 LHsType GhcRn
ty2 Type
exp_kind = case TcTyMode -> TypeOrKind
mode_tyki TcTyMode
mode of
  TypeOrKind
TypeLevel ->
    do { Type
arg_k <- TcM Type
newOpenTypeKind
       ; Type
res_k <- TcM Type
newOpenTypeKind
       ; Type
ty1' <- TcTyMode -> LHsType GhcRn -> Type -> TcM Type
tc_lhs_type TcTyMode
mode LHsType GhcRn
ty1 Type
arg_k
       ; Type
ty2' <- TcTyMode -> LHsType GhcRn -> Type -> TcM Type
tc_lhs_type TcTyMode
mode LHsType GhcRn
ty2 Type
res_k
       ; Type
mult' <- TcTyMode -> HsArrow GhcRn -> TcM Type
tc_mult TcTyMode
mode HsArrow GhcRn
mult
       ; HasDebugCallStack =>
HsType GhcRn -> Type -> Type -> Type -> TcM Type
HsType GhcRn -> Type -> Type -> Type -> TcM Type
checkExpectedKind (XFunTy GhcRn
-> HsArrow GhcRn -> LHsType GhcRn -> LHsType GhcRn -> HsType GhcRn
forall pass.
XFunTy pass
-> HsArrow pass -> LHsType pass -> LHsType pass -> HsType pass
HsFunTy XFunTy GhcRn
forall a. EpAnn a
noAnn HsArrow GhcRn
mult LHsType GhcRn
ty1 LHsType GhcRn
ty2) (Type -> Type -> Type -> Type
mkVisFunTy Type
mult' Type
ty1' Type
ty2')
                           Type
liftedTypeKind Type
exp_kind }
  TypeOrKind
KindLevel ->  -- no representation polymorphism in kinds. yet.
    do { Type
ty1' <- TcTyMode -> LHsType GhcRn -> Type -> TcM Type
tc_lhs_type TcTyMode
mode LHsType GhcRn
ty1 Type
liftedTypeKind
       ; Type
ty2' <- TcTyMode -> LHsType GhcRn -> Type -> TcM Type
tc_lhs_type TcTyMode
mode LHsType GhcRn
ty2 Type
liftedTypeKind
       ; Type
mult' <- TcTyMode -> HsArrow GhcRn -> TcM Type
tc_mult TcTyMode
mode HsArrow GhcRn
mult
       ; HasDebugCallStack =>
HsType GhcRn -> Type -> Type -> Type -> TcM Type
HsType GhcRn -> Type -> Type -> Type -> TcM Type
checkExpectedKind (XFunTy GhcRn
-> HsArrow GhcRn -> LHsType GhcRn -> LHsType GhcRn -> HsType GhcRn
forall pass.
XFunTy pass
-> HsArrow pass -> LHsType pass -> LHsType pass -> HsType pass
HsFunTy XFunTy GhcRn
forall a. EpAnn a
noAnn HsArrow GhcRn
mult LHsType GhcRn
ty1 LHsType GhcRn
ty2) (Type -> Type -> Type -> Type
mkVisFunTy Type
mult' Type
ty1' Type
ty2')
                           Type
liftedTypeKind Type
exp_kind }

{- Note [Skolem escape and forall-types]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
See also Note [Checking telescopes].

Consider
  f :: forall a. (forall kb (b :: kb). Proxy '[a, b]) -> ()

The Proxy '[a,b] forces a and b to have the same kind.  But a's
kind must be bound outside the 'forall a', and hence escapes.
We discover this by building an implication constraint for
each forall.  So the inner implication constraint will look like
    forall kb (b::kb).  kb ~ ka
where ka is a's kind.  We can't unify these two, /even/ if ka is
unification variable, because it would be untouchable inside
this inner implication.

That's what the pushLevelAndCaptureConstraints, plus subsequent
buildTvImplication/emitImplication is all about, when kind-checking
HsForAllTy.

Note that

* We don't need to /simplify/ the constraints here
  because we aren't generalising. We just capture them.

* We can't use emitResidualTvConstraint, because that has a fast-path
  for empty constraints.  We can't take that fast path here, because
  we must do the bad-telescope check even if there are no inner wanted
  constraints. See Note [Checking telescopes] in
  GHC.Tc.Types.Constraint.  Lacking this check led to #16247.
-}

{- *********************************************************************
*                                                                      *
                Tuples
*                                                                      *
********************************************************************* -}

---------------------------
tupKindSort_maybe :: TcKind -> Maybe TupleSort
tupKindSort_maybe :: Type -> Maybe TupleSort
tupKindSort_maybe Type
k
  | Just (Type
k', Coercion
_) <- Type -> Maybe (Type, Coercion)
splitCastTy_maybe Type
k = Type -> Maybe TupleSort
tupKindSort_maybe Type
k'
  | Just Type
k'      <- Type -> Maybe Type
tcView Type
k            = Type -> Maybe TupleSort
tupKindSort_maybe Type
k'
  | Type -> Bool
tcIsConstraintKind Type
k = TupleSort -> Maybe TupleSort
forall a. a -> Maybe a
Just TupleSort
ConstraintTuple
  | Type -> Bool
tcIsLiftedTypeKind Type
k   = TupleSort -> Maybe TupleSort
forall a. a -> Maybe a
Just TupleSort
BoxedTuple
  | Bool
otherwise            = Maybe TupleSort
forall a. Maybe a
Nothing

tc_tuple :: HsType GhcRn -> TcTyMode -> TupleSort -> [LHsType GhcRn] -> TcKind -> TcM TcType
tc_tuple :: HsType GhcRn
-> TcTyMode -> TupleSort -> [LHsType GhcRn] -> Type -> TcM Type
tc_tuple HsType GhcRn
rn_ty TcTyMode
mode TupleSort
tup_sort [LHsType GhcRn]
tys Type
exp_kind
  = do { [Type]
arg_kinds <- case TupleSort
tup_sort of
           TupleSort
BoxedTuple      -> [Type] -> TcM [Type]
forall (m :: * -> *) a. Monad m => a -> m a
return (Arity -> Type -> [Type]
forall a. Arity -> a -> [a]
replicate Arity
arity Type
liftedTypeKind)
           TupleSort
UnboxedTuple    -> Arity -> TcM Type -> TcM [Type]
forall (m :: * -> *) a. Applicative m => Arity -> m a -> m [a]
replicateM Arity
arity TcM Type
newOpenTypeKind
           TupleSort
ConstraintTuple -> [Type] -> TcM [Type]
forall (m :: * -> *) a. Monad m => a -> m a
return (Arity -> Type -> [Type]
forall a. Arity -> a -> [a]
replicate Arity
arity Type
constraintKind)
       ; [Type]
tau_tys <- (GenLocated SrcSpanAnnA (HsType GhcRn) -> Type -> TcM Type)
-> [GenLocated SrcSpanAnnA (HsType GhcRn)] -> [Type] -> TcM [Type]
forall (m :: * -> *) a b c.
Applicative m =>
(a -> b -> m c) -> [a] -> [b] -> m [c]
zipWithM (TcTyMode -> LHsType GhcRn -> Type -> TcM Type
tc_lhs_type TcTyMode
mode) [GenLocated SrcSpanAnnA (HsType GhcRn)]
[LHsType GhcRn]
tys [Type]
arg_kinds
       ; HsType GhcRn -> TupleSort -> [Type] -> [Type] -> Type -> TcM Type
finish_tuple HsType GhcRn
rn_ty TupleSort
tup_sort [Type]
tau_tys [Type]
arg_kinds Type
exp_kind }
  where
    arity :: Arity
arity   = [GenLocated SrcSpanAnnA (HsType GhcRn)] -> Arity
forall (t :: * -> *) a. Foldable t => t a -> Arity
length [GenLocated SrcSpanAnnA (HsType GhcRn)]
[LHsType GhcRn]
tys

finish_tuple :: HsType GhcRn
             -> TupleSort
             -> [TcType]    -- ^ argument types
             -> [TcKind]    -- ^ of these kinds
             -> TcKind      -- ^ expected kind of the whole tuple
             -> TcM TcType
finish_tuple :: HsType GhcRn -> TupleSort -> [Type] -> [Type] -> Type -> TcM Type
finish_tuple HsType GhcRn
rn_ty TupleSort
tup_sort [Type]
tau_tys [Type]
tau_kinds Type
exp_kind = do
  String -> SDoc -> TcM ()
traceTc String
"finish_tuple" (TupleSort -> SDoc
forall a. Outputable a => a -> SDoc
ppr TupleSort
tup_sort SDoc -> SDoc -> SDoc
$$ [Type] -> SDoc
forall a. Outputable a => a -> SDoc
ppr [Type]
tau_kinds SDoc -> SDoc -> SDoc
$$ Type -> SDoc
forall a. Outputable a => a -> SDoc
ppr Type
exp_kind)
  case TupleSort
tup_sort of
    TupleSort
ConstraintTuple
      |  [Type
tau_ty] <- [Type]
tau_tys
         -- Drop any uses of 1-tuple constraints here.
         -- See Note [Ignore unary constraint tuples]
      -> Type -> Type -> TcM Type
check_expected_kind Type
tau_ty Type
constraintKind
      |  Bool
otherwise
      -> do let tycon :: TyCon
tycon = Arity -> TyCon
cTupleTyCon Arity
arity
            Arity -> TcM ()
checkCTupSize Arity
arity
            Type -> Type -> TcM Type
check_expected_kind (TyCon -> [Type] -> Type
mkTyConApp TyCon
tycon [Type]
tau_tys) Type
constraintKind
    TupleSort
BoxedTuple -> do
      let tycon :: TyCon
tycon = Boxity -> Arity -> TyCon
tupleTyCon Boxity
Boxed Arity
arity
      Arity -> TcM ()
checkTupSize Arity
arity
      TyCon -> TcM ()
checkWiredInTyCon TyCon
tycon
      Type -> Type -> TcM Type
check_expected_kind (TyCon -> [Type] -> Type
mkTyConApp TyCon
tycon [Type]
tau_tys) Type
liftedTypeKind
    TupleSort
UnboxedTuple -> do
      let tycon :: TyCon
tycon    = Boxity -> Arity -> TyCon
tupleTyCon Boxity
Unboxed Arity
arity
          tau_reps :: [Type]
tau_reps = (Type -> Type) -> [Type] -> [Type]
forall a b. (a -> b) -> [a] -> [b]
map HasDebugCallStack => Type -> Type
Type -> Type
kindRep [Type]
tau_kinds
          -- See also Note [Unboxed tuple RuntimeRep vars] in GHC.Core.TyCon
          arg_tys :: [Type]
arg_tys  = [Type]
tau_reps [Type] -> [Type] -> [Type]
forall a. [a] -> [a] -> [a]
++ [Type]
tau_tys
          res_kind :: Type
res_kind = [Type] -> Type
unboxedTupleKind [Type]
tau_reps
      Arity -> TcM ()
checkTupSize Arity
arity
      Type -> Type -> TcM Type
check_expected_kind (TyCon -> [Type] -> Type
mkTyConApp TyCon
tycon [Type]
arg_tys) Type
res_kind
  where
    arity :: Arity
arity = [Type] -> Arity
forall (t :: * -> *) a. Foldable t => t a -> Arity
length [Type]
tau_tys
    check_expected_kind :: Type -> Type -> TcM Type
check_expected_kind Type
ty Type
act_kind =
      HasDebugCallStack =>
HsType GhcRn -> Type -> Type -> Type -> TcM Type
HsType GhcRn -> Type -> Type -> Type -> TcM Type
checkExpectedKind HsType GhcRn
rn_ty Type
ty Type
act_kind Type
exp_kind

{-
Note [Ignore unary constraint tuples]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
GHC provides unary tuples and unboxed tuples (see Note [One-tuples] in
GHC.Builtin.Types) but does *not* provide unary constraint tuples. Why? First,
recall the definition of a unary tuple data type:

  data Solo a = Solo a

Note that `Solo a` is *not* the same thing as `a`, since Solo is boxed and
lazy. Therefore, the presence of `Solo` matters semantically. On the other
hand, suppose we had a unary constraint tuple:

  class a => Solo% a

This compiles down a newtype (i.e., a cast) in Core, so `Solo% a` is
semantically equivalent to `a`. Therefore, a 1-tuple constraint would have
no user-visible impact, nor would it allow you to express anything that
you couldn't otherwise.

We could simply add Solo% for consistency with tuples (Solo) and unboxed
tuples (Solo#), but that would require even more magic to wire in another
magical class, so we opt not to do so. We must be careful, however, since
one can try to sneak in uses of unary constraint tuples through Template
Haskell, such as in this program (from #17511):

  f :: $(pure (ForallT [] [TupleT 1 `AppT` (ConT ''Show `AppT` ConT ''Int)]
                       (ConT ''String)))
  -- f :: Solo% (Show Int) => String
  f = "abc"

This use of `TupleT 1` will produce an HsBoxedOrConstraintTuple of arity 1,
and since it is used in a Constraint position, GHC will attempt to treat
it as thought it were a constraint tuple, which can potentially lead to
trouble if one attempts to look up the name of a constraint tuple of arity
1 (as it won't exist). To avoid this trouble, we simply take any unary
constraint tuples discovered when typechecking and drop them—i.e., treat
"Solo% a" as though the user had written "a". This is always safe to do
since the two constraints should be semantically equivalent.
-}

{- *********************************************************************
*                                                                      *
                Type applications
*                                                                      *
********************************************************************* -}

splitHsAppTys :: HsType GhcRn -> Maybe (LHsType GhcRn, [LHsTypeArg GhcRn])
splitHsAppTys :: HsType GhcRn -> Maybe (LHsType GhcRn, HsTyPats GhcRn)
splitHsAppTys HsType GhcRn
hs_ty
  | HsType GhcRn -> Bool
is_app HsType GhcRn
hs_ty = (GenLocated SrcSpanAnnA (HsType GhcRn),
 [HsArg
    (GenLocated SrcSpanAnnA (HsType GhcRn))
    (GenLocated SrcSpanAnnA (HsType GhcRn))])
-> Maybe
     (GenLocated SrcSpanAnnA (HsType GhcRn),
      [HsArg
         (GenLocated SrcSpanAnnA (HsType GhcRn))
         (GenLocated SrcSpanAnnA (HsType GhcRn))])
forall a. a -> Maybe a
Just (LHsType GhcRn -> HsTyPats GhcRn -> (LHsType GhcRn, HsTyPats GhcRn)
go (HsType GhcRn -> GenLocated SrcSpanAnnA (HsType GhcRn)
forall a an. a -> LocatedAn an a
noLocA HsType GhcRn
hs_ty) [])
  | Bool
otherwise    = Maybe (LHsType GhcRn, HsTyPats GhcRn)
forall a. Maybe a
Nothing
  where
    is_app :: HsType GhcRn -> Bool
    is_app :: HsType GhcRn -> Bool
is_app (HsAppKindTy {})        = Bool
True
    is_app (HsAppTy {})            = Bool
True
    is_app (HsOpTy XOpTy GhcRn
_ LHsType GhcRn
_ (L SrcSpanAnnN
_ Name
op) LHsType GhcRn
_) = Bool -> Bool
not (Name
op Name -> Unique -> Bool
forall a. Uniquable a => a -> Unique -> Bool
`hasKey` Unique
funTyConKey)
      -- I'm not sure why this funTyConKey test is necessary
      -- Can it even happen?  Perhaps for   t1 `(->)` t2
      -- but then maybe it's ok to treat that like a normal
      -- application rather than using the special rule for HsFunTy
    is_app (HsTyVar {})            = Bool
True
    is_app (HsParTy XParTy GhcRn
_ (L SrcSpanAnnA
_ HsType GhcRn
ty))    = HsType GhcRn -> Bool
is_app HsType GhcRn
ty
    is_app HsType GhcRn
_                       = Bool
False

    go :: LHsType GhcRn
       -> [HsArg (LHsType GhcRn) (LHsKind GhcRn)]
       -> (LHsType GhcRn,
           [HsArg (LHsType GhcRn) (LHsKind GhcRn)]) -- AZ temp
    go :: LHsType GhcRn -> HsTyPats GhcRn -> (LHsType GhcRn, HsTyPats GhcRn)
go (L SrcSpanAnnA
_  (HsAppTy XAppTy GhcRn
_ LHsType GhcRn
f LHsType GhcRn
a))      HsTyPats GhcRn
as = LHsType GhcRn -> HsTyPats GhcRn -> (LHsType GhcRn, HsTyPats GhcRn)
go LHsType GhcRn
f (GenLocated SrcSpanAnnA (HsType GhcRn)
-> HsArg
     (GenLocated SrcSpanAnnA (HsType GhcRn))
     (GenLocated SrcSpanAnnA (HsType GhcRn))
forall tm ty. tm -> HsArg tm ty
HsValArg GenLocated SrcSpanAnnA (HsType GhcRn)
LHsType GhcRn
a HsArg
  (GenLocated SrcSpanAnnA (HsType GhcRn))
  (GenLocated SrcSpanAnnA (HsType GhcRn))
-> [HsArg
      (GenLocated SrcSpanAnnA (HsType GhcRn))
      (GenLocated SrcSpanAnnA (HsType GhcRn))]
-> [HsArg
      (GenLocated SrcSpanAnnA (HsType GhcRn))
      (GenLocated SrcSpanAnnA (HsType GhcRn))]
forall a. a -> [a] -> [a]
: [HsArg
   (GenLocated SrcSpanAnnA (HsType GhcRn))
   (GenLocated SrcSpanAnnA (HsType GhcRn))]
HsTyPats GhcRn
as)
    go (L SrcSpanAnnA
_  (HsAppKindTy XAppKindTy GhcRn
l LHsType GhcRn
ty LHsType GhcRn
k)) HsTyPats GhcRn
as = LHsType GhcRn -> HsTyPats GhcRn -> (LHsType GhcRn, HsTyPats GhcRn)
go LHsType GhcRn
ty (SrcSpan
-> GenLocated SrcSpanAnnA (HsType GhcRn)
-> HsArg
     (GenLocated SrcSpanAnnA (HsType GhcRn))
     (GenLocated SrcSpanAnnA (HsType GhcRn))
forall tm ty. SrcSpan -> ty -> HsArg tm ty
HsTypeArg SrcSpan
XAppKindTy GhcRn
l GenLocated SrcSpanAnnA (HsType GhcRn)
LHsType GhcRn
k HsArg
  (GenLocated SrcSpanAnnA (HsType GhcRn))
  (GenLocated SrcSpanAnnA (HsType GhcRn))
-> [HsArg
      (GenLocated SrcSpanAnnA (HsType GhcRn))
      (GenLocated SrcSpanAnnA (HsType GhcRn))]
-> [HsArg
      (GenLocated SrcSpanAnnA (HsType GhcRn))
      (GenLocated SrcSpanAnnA (HsType GhcRn))]
forall a. a -> [a] -> [a]
: [HsArg
   (GenLocated SrcSpanAnnA (HsType GhcRn))
   (GenLocated SrcSpanAnnA (HsType GhcRn))]
HsTyPats GhcRn
as)
    go (L SrcSpanAnnA
sp (HsParTy XParTy GhcRn
_ LHsType GhcRn
f))        HsTyPats GhcRn
as = LHsType GhcRn -> HsTyPats GhcRn -> (LHsType GhcRn, HsTyPats GhcRn)
go LHsType GhcRn
f (SrcSpan
-> HsArg
     (GenLocated SrcSpanAnnA (HsType GhcRn))
     (GenLocated SrcSpanAnnA (HsType GhcRn))
forall tm ty. SrcSpan -> HsArg tm ty
HsArgPar (SrcSpanAnnA -> SrcSpan
forall a. SrcSpanAnn' a -> SrcSpan
locA SrcSpanAnnA
sp) HsArg
  (GenLocated SrcSpanAnnA (HsType GhcRn))
  (GenLocated SrcSpanAnnA (HsType GhcRn))
-> [HsArg
      (GenLocated SrcSpanAnnA (HsType GhcRn))
      (GenLocated SrcSpanAnnA (HsType GhcRn))]
-> [HsArg
      (GenLocated SrcSpanAnnA (HsType GhcRn))
      (GenLocated SrcSpanAnnA (HsType GhcRn))]
forall a. a -> [a] -> [a]
: [HsArg
   (GenLocated SrcSpanAnnA (HsType GhcRn))
   (GenLocated SrcSpanAnnA (HsType GhcRn))]
HsTyPats GhcRn
as)
    go (L SrcSpanAnnA
_  (HsOpTy XOpTy GhcRn
_ LHsType GhcRn
l op :: LIdP GhcRn
op@(L SrcSpanAnnN
sp Name
_) LHsType GhcRn
r)) HsTyPats GhcRn
as
      = ( SrcSpanAnnA
-> HsType GhcRn -> GenLocated SrcSpanAnnA (HsType GhcRn)
forall l e. l -> e -> GenLocated l e
L (SrcSpanAnnN -> SrcSpanAnnA
forall a ann. SrcSpanAnn' a -> SrcAnn ann
na2la SrcSpanAnnN
sp) (XTyVar GhcRn -> PromotionFlag -> LIdP GhcRn -> HsType GhcRn
forall pass.
XTyVar pass -> PromotionFlag -> LIdP pass -> HsType pass
HsTyVar XTyVar GhcRn
forall a. EpAnn a
noAnn PromotionFlag
NotPromoted LIdP GhcRn
op)
        , GenLocated SrcSpanAnnA (HsType GhcRn)
-> HsArg
     (GenLocated SrcSpanAnnA (HsType GhcRn))
     (GenLocated SrcSpanAnnA (HsType GhcRn))
forall tm ty. tm -> HsArg tm ty
HsValArg GenLocated SrcSpanAnnA (HsType GhcRn)
LHsType GhcRn
l HsArg
  (GenLocated SrcSpanAnnA (HsType GhcRn))
  (GenLocated SrcSpanAnnA (HsType GhcRn))
-> [HsArg
      (GenLocated SrcSpanAnnA (HsType GhcRn))
      (GenLocated SrcSpanAnnA (HsType GhcRn))]
-> [HsArg
      (GenLocated SrcSpanAnnA (HsType GhcRn))
      (GenLocated SrcSpanAnnA (HsType GhcRn))]
forall a. a -> [a] -> [a]
: GenLocated SrcSpanAnnA (HsType GhcRn)
-> HsArg
     (GenLocated SrcSpanAnnA (HsType GhcRn))
     (GenLocated SrcSpanAnnA (HsType GhcRn))
forall tm ty. tm -> HsArg tm ty
HsValArg GenLocated SrcSpanAnnA (HsType GhcRn)
LHsType GhcRn
r HsArg
  (GenLocated SrcSpanAnnA (HsType GhcRn))
  (GenLocated SrcSpanAnnA (HsType GhcRn))
-> [HsArg
      (GenLocated SrcSpanAnnA (HsType GhcRn))
      (GenLocated SrcSpanAnnA (HsType GhcRn))]
-> [HsArg
      (GenLocated SrcSpanAnnA (HsType GhcRn))
      (GenLocated SrcSpanAnnA (HsType GhcRn))]
forall a. a -> [a] -> [a]
: [HsArg
   (GenLocated SrcSpanAnnA (HsType GhcRn))
   (GenLocated SrcSpanAnnA (HsType GhcRn))]
HsTyPats GhcRn
as )
    go LHsType GhcRn
f HsTyPats GhcRn
as = (LHsType GhcRn
f, HsTyPats GhcRn
as)

---------------------------
tcInferTyAppHead :: TcTyMode -> LHsType GhcRn -> TcM (TcType, TcKind)
-- Version of tc_infer_lhs_type specialised for the head of an
-- application. In particular, for a HsTyVar (which includes type
-- constructors, it does not zoom off into tcInferTyApps and family
-- saturation
tcInferTyAppHead :: TcTyMode -> LHsType GhcRn -> TcM (Type, Type)
tcInferTyAppHead TcTyMode
mode (L SrcSpanAnnA
_ (HsTyVar XTyVar GhcRn
_ PromotionFlag
_ (L SrcSpanAnnN
_ Name
tv)))
  = TcTyMode -> Name -> TcM (Type, Type)
tcTyVar TcTyMode
mode Name
tv
tcInferTyAppHead TcTyMode
mode LHsType GhcRn
ty
  = TcTyMode -> LHsType GhcRn -> TcM (Type, Type)
tc_infer_lhs_type TcTyMode
mode LHsType GhcRn
ty

---------------------------
-- | Apply a type of a given kind to a list of arguments. This instantiates
-- invisible parameters as necessary. Always consumes all the arguments,
-- using matchExpectedFunKind as necessary.
-- This takes an optional @VarEnv Kind@ which maps kind variables to kinds.-
-- These kinds should be used to instantiate invisible kind variables;
-- they come from an enclosing class for an associated type/data family.
--
-- tcInferTyApps also arranges to saturate any trailing invisible arguments
--   of a type-family application, which is usually the right thing to do
-- tcInferTyApps_nosat does not do this saturation; it is used only
--   by ":kind" in GHCi
tcInferTyApps, tcInferTyApps_nosat
    :: TcTyMode
    -> LHsType GhcRn        -- ^ Function (for printing only)
    -> TcType               -- ^ Function
    -> [LHsTypeArg GhcRn]   -- ^ Args
    -> TcM (TcType, TcKind) -- ^ (f args, args, result kind)
tcInferTyApps :: TcTyMode
-> LHsType GhcRn -> Type -> HsTyPats GhcRn -> TcM (Type, Type)
tcInferTyApps TcTyMode
mode LHsType GhcRn
hs_ty Type
fun HsTyPats GhcRn
hs_args
  = do { (Type
f_args, Type
res_k) <- TcTyMode
-> LHsType GhcRn -> Type -> HsTyPats GhcRn -> TcM (Type, Type)
tcInferTyApps_nosat TcTyMode
mode LHsType GhcRn
hs_ty Type
fun HsTyPats GhcRn
hs_args
       ; Type -> Type -> TcM (Type, Type)
saturateFamApp Type
f_args Type
res_k }

tcInferTyApps_nosat :: TcTyMode
-> LHsType GhcRn -> Type -> HsTyPats GhcRn -> TcM (Type, Type)
tcInferTyApps_nosat TcTyMode
mode LHsType GhcRn
orig_hs_ty Type
fun HsTyPats GhcRn
orig_hs_args
  = do { String -> SDoc -> TcM ()
traceTc String
"tcInferTyApps {" (GenLocated SrcSpanAnnA (HsType GhcRn) -> SDoc
forall a. Outputable a => a -> SDoc
ppr GenLocated SrcSpanAnnA (HsType GhcRn)
LHsType GhcRn
orig_hs_ty SDoc -> SDoc -> SDoc
$$ [HsArg
   (GenLocated SrcSpanAnnA (HsType GhcRn))
   (GenLocated SrcSpanAnnA (HsType GhcRn))]
-> SDoc
forall a. Outputable a => a -> SDoc
ppr [HsArg
   (GenLocated SrcSpanAnnA (HsType GhcRn))
   (GenLocated SrcSpanAnnA (HsType GhcRn))]
HsTyPats GhcRn
orig_hs_args)
       ; (Type
f_args, Type
res_k) <- Arity
-> Type
-> [HsArg
      (GenLocated SrcSpanAnnA (HsType GhcRn))
      (GenLocated SrcSpanAnnA (HsType GhcRn))]
-> TcM (Type, Type)
go_init Arity
1 Type
fun [HsArg
   (GenLocated SrcSpanAnnA (HsType GhcRn))
   (GenLocated SrcSpanAnnA (HsType GhcRn))]
HsTyPats GhcRn
orig_hs_args
       ; String -> SDoc -> TcM ()
traceTc String
"tcInferTyApps }" (Type -> SDoc
forall a. Outputable a => a -> SDoc
ppr Type
f_args SDoc -> SDoc -> SDoc
<+> SDoc
dcolon SDoc -> SDoc -> SDoc
<+> Type -> SDoc
forall a. Outputable a => a -> SDoc
ppr Type
res_k)
       ; (Type, Type) -> TcM (Type, Type)
forall (m :: * -> *) a. Monad m => a -> m a
return (Type
f_args, Type
res_k) }
  where

    -- go_init just initialises the auxiliary
    -- arguments of the 'go' loop
    go_init :: Arity
-> Type
-> [HsArg
      (GenLocated SrcSpanAnnA (HsType GhcRn))
      (GenLocated SrcSpanAnnA (HsType GhcRn))]
-> TcM (Type, Type)
go_init Arity
n Type
fun [HsArg
   (GenLocated SrcSpanAnnA (HsType GhcRn))
   (GenLocated SrcSpanAnnA (HsType GhcRn))]
all_args
      = Arity
-> Type -> TCvSubst -> Type -> HsTyPats GhcRn -> TcM (Type, Type)
go Arity
n Type
fun TCvSubst
empty_subst Type
fun_ki [HsArg
   (GenLocated SrcSpanAnnA (HsType GhcRn))
   (GenLocated SrcSpanAnnA (HsType GhcRn))]
HsTyPats GhcRn
all_args
      where
        fun_ki :: Type
fun_ki = HasDebugCallStack => Type -> Type
Type -> Type
tcTypeKind Type
fun
           -- We do (tcTypeKind fun) here, even though the caller
           -- knows the function kind, to absolutely guarantee
           -- INVARIANT for 'go'
           -- Note that in a typical application (F t1 t2 t3),
           -- the 'fun' is just a TyCon, so tcTypeKind is fast

        empty_subst :: TCvSubst
empty_subst = InScopeSet -> TCvSubst
mkEmptyTCvSubst (InScopeSet -> TCvSubst) -> InScopeSet -> TCvSubst
forall a b. (a -> b) -> a -> b
$ VarSet -> InScopeSet
mkInScopeSet (VarSet -> InScopeSet) -> VarSet -> InScopeSet
forall a b. (a -> b) -> a -> b
$
                      Type -> VarSet
tyCoVarsOfType Type
fun_ki

    go :: Int             -- The # of the next argument
       -> TcType          -- Function applied to some args
       -> TCvSubst        -- Applies to function kind
       -> TcKind          -- Function kind
       -> [LHsTypeArg GhcRn]    -- Un-type-checked args
       -> TcM (TcType, TcKind)  -- Result type and its kind
    -- INVARIANT: in any call (go n fun subst fun_ki args)
    --               tcTypeKind fun  =  subst(fun_ki)
    -- So the 'subst' and 'fun_ki' arguments are simply
    -- there to avoid repeatedly calling tcTypeKind.
    --
    -- Reason for INVARIANT: to support the Purely Kinded Type Invariant
    -- it's important that if fun_ki has a forall, then so does
    -- (tcTypeKind fun), because the next thing we are going to do
    -- is apply 'fun' to an argument type.

    -- Dispatch on all_args first, for performance reasons
    go :: Arity
-> Type -> TCvSubst -> Type -> HsTyPats GhcRn -> TcM (Type, Type)
go Arity
n Type
fun TCvSubst
subst Type
fun_ki HsTyPats GhcRn
all_args = case ([HsArg
   (GenLocated SrcSpanAnnA (HsType GhcRn))
   (GenLocated SrcSpanAnnA (HsType GhcRn))]
HsTyPats GhcRn
all_args, Type -> Maybe (TyBinder, Type)
tcSplitPiTy_maybe Type
fun_ki) of

      ---------------- No user-written args left. We're done!
      ([], Maybe (TyBinder, Type)
_) -> (Type, Type) -> TcM (Type, Type)
forall (m :: * -> *) a. Monad m => a -> m a
return (Type
fun, HasCallStack => TCvSubst -> Type -> Type
TCvSubst -> Type -> Type
substTy TCvSubst
subst Type
fun_ki)

      ---------------- HsArgPar: We don't care about parens here
      (HsArgPar SrcSpan
_ : [HsArg
   (GenLocated SrcSpanAnnA (HsType GhcRn))
   (GenLocated SrcSpanAnnA (HsType GhcRn))]
args, Maybe (TyBinder, Type)
_) -> Arity
-> Type -> TCvSubst -> Type -> HsTyPats GhcRn -> TcM (Type, Type)
go Arity
n Type
fun TCvSubst
subst Type
fun_ki [HsArg
   (GenLocated SrcSpanAnnA (HsType GhcRn))
   (GenLocated SrcSpanAnnA (HsType GhcRn))]
HsTyPats GhcRn
args

      ---------------- HsTypeArg: a kind application (fun @ki)
      (HsTypeArg SrcSpan
_ GenLocated SrcSpanAnnA (HsType GhcRn)
hs_ki_arg : [HsArg
   (GenLocated SrcSpanAnnA (HsType GhcRn))
   (GenLocated SrcSpanAnnA (HsType GhcRn))]
hs_args, Just (TyBinder
ki_binder, Type
inner_ki)) ->
        case TyBinder
ki_binder of

        -- FunTy with PredTy on LHS, or ForAllTy with Inferred
        Named (Bndr TyVar
_ ArgFlag
Inferred) -> TyBinder -> Type -> TcM (Type, Type)
instantiate TyBinder
ki_binder Type
inner_ki
        Anon AnonArgFlag
InvisArg Scaled Type
_         -> TyBinder -> Type -> TcM (Type, Type)
instantiate TyBinder
ki_binder Type
inner_ki

        Named (Bndr TyVar
_ ArgFlag
Specified) ->  -- Visible kind application
          do { String -> SDoc -> TcM ()
traceTc String
"tcInferTyApps (vis kind app)"
                       ([SDoc] -> SDoc
vcat [ TyBinder -> SDoc
forall a. Outputable a => a -> SDoc
ppr TyBinder
ki_binder, GenLocated SrcSpanAnnA (HsType GhcRn) -> SDoc
forall a. Outputable a => a -> SDoc
ppr GenLocated SrcSpanAnnA (HsType GhcRn)
hs_ki_arg
                             , Type -> SDoc
forall a. Outputable a => a -> SDoc
ppr (TyBinder -> Type
tyBinderType TyBinder
ki_binder)
                             , TCvSubst -> SDoc
forall a. Outputable a => a -> SDoc
ppr TCvSubst
subst ])

             ; let exp_kind :: Type
exp_kind = HasCallStack => TCvSubst -> Type -> Type
TCvSubst -> Type -> Type
substTy TCvSubst
subst (Type -> Type) -> Type -> Type
forall a b. (a -> b) -> a -> b
$ TyBinder -> Type
tyBinderType TyBinder
ki_binder
             ; TcTyMode
arg_mode <- TypeOrKind -> HoleMode -> TcM TcTyMode
mkHoleMode TypeOrKind
KindLevel HoleMode
HM_VTA
                   -- HM_VKA: see Note [Wildcards in visible kind application]
             ; Type
ki_arg <- SDoc -> TcM Type -> TcM Type
forall a. SDoc -> TcM a -> TcM a
addErrCtxt (GenLocated SrcSpanAnnA (HsType GhcRn)
-> GenLocated SrcSpanAnnA (HsType GhcRn) -> Arity -> SDoc
forall fun arg.
(Outputable fun, Outputable arg) =>
fun -> arg -> Arity -> SDoc
funAppCtxt GenLocated SrcSpanAnnA (HsType GhcRn)
LHsType GhcRn
orig_hs_ty GenLocated SrcSpanAnnA (HsType GhcRn)
hs_ki_arg Arity
n) (TcM Type -> TcM Type) -> TcM Type -> TcM Type
forall a b. (a -> b) -> a -> b
$
                         TcTyMode -> LHsType GhcRn -> Type -> TcM Type
tc_lhs_type TcTyMode
arg_mode GenLocated SrcSpanAnnA (HsType GhcRn)
LHsType GhcRn
hs_ki_arg Type
exp_kind

             ; String -> SDoc -> TcM ()
traceTc String
"tcInferTyApps (vis kind app)" (Type -> SDoc
forall a. Outputable a => a -> SDoc
ppr Type
exp_kind)
             ; (TCvSubst
subst', Type
fun') <- TCvSubst -> Type -> TyBinder -> Type -> TcM (TCvSubst, Type)
mkAppTyM TCvSubst
subst Type
fun TyBinder
ki_binder Type
ki_arg
             ; Arity
-> Type -> TCvSubst -> Type -> HsTyPats GhcRn -> TcM (Type, Type)
go (Arity
nArity -> Arity -> Arity
forall a. Num a => a -> a -> a
+Arity
1) Type
fun' TCvSubst
subst' Type
inner_ki [HsArg
   (GenLocated SrcSpanAnnA (HsType GhcRn))
   (GenLocated SrcSpanAnnA (HsType GhcRn))]
HsTyPats GhcRn
hs_args }

        -- Attempted visible kind application (fun @ki), but fun_ki is
        --   forall k -> blah   or   k1 -> k2
        -- So we need a normal application.  Error.
        TyBinder
_ -> GenLocated SrcSpanAnnA (HsType GhcRn) -> Type -> TcM (Type, Type)
forall {a} {a} {a}.
(Outputable a, Outputable a) =>
a -> a -> TcRn a
ty_app_err GenLocated SrcSpanAnnA (HsType GhcRn)
hs_ki_arg (Type -> TcM (Type, Type)) -> Type -> TcM (Type, Type)
forall a b. (a -> b) -> a -> b
$ HasCallStack => TCvSubst -> Type -> Type
TCvSubst -> Type -> Type
substTy TCvSubst
subst Type
fun_ki

      -- No binder; try applying the substitution, or fail if that's not possible
      (HsTypeArg SrcSpan
_ GenLocated SrcSpanAnnA (HsType GhcRn)
ki_arg : [HsArg
   (GenLocated SrcSpanAnnA (HsType GhcRn))
   (GenLocated SrcSpanAnnA (HsType GhcRn))]
_, Maybe (TyBinder, Type)
Nothing) -> TcM (Type, Type) -> TcM (Type, Type)
try_again_after_substing_or (TcM (Type, Type) -> TcM (Type, Type))
-> TcM (Type, Type) -> TcM (Type, Type)
forall a b. (a -> b) -> a -> b
$
                                           GenLocated SrcSpanAnnA (HsType GhcRn) -> Type -> TcM (Type, Type)
forall {a} {a} {a}.
(Outputable a, Outputable a) =>
a -> a -> TcRn a
ty_app_err GenLocated SrcSpanAnnA (HsType GhcRn)
ki_arg Type
substed_fun_ki

      ---------------- HsValArg: a normal argument (fun ty)
      (HsValArg GenLocated SrcSpanAnnA (HsType GhcRn)
arg : [HsArg
   (GenLocated SrcSpanAnnA (HsType GhcRn))
   (GenLocated SrcSpanAnnA (HsType GhcRn))]
args, Just (TyBinder
ki_binder, Type
inner_ki))
        -- next binder is invisible; need to instantiate it
        | TyBinder -> Bool
isInvisibleBinder TyBinder
ki_binder   -- FunTy with InvisArg on LHS;
                                        -- or ForAllTy with Inferred or Specified
         -> TyBinder -> Type -> TcM (Type, Type)
instantiate TyBinder
ki_binder Type
inner_ki

        -- "normal" case
        | Bool
otherwise
         -> do { String -> SDoc -> TcM ()
traceTc String
"tcInferTyApps (vis normal app)"
                          ([SDoc] -> SDoc
vcat [ TyBinder -> SDoc
forall a. Outputable a => a -> SDoc
ppr TyBinder
ki_binder
                                , GenLocated SrcSpanAnnA (HsType GhcRn) -> SDoc
forall a. Outputable a => a -> SDoc
ppr GenLocated SrcSpanAnnA (HsType GhcRn)
arg
                                , Type -> SDoc
forall a. Outputable a => a -> SDoc
ppr (TyBinder -> Type
tyBinderType TyBinder
ki_binder)
                                , TCvSubst -> SDoc
forall a. Outputable a => a -> SDoc
ppr TCvSubst
subst ])
                ; let exp_kind :: Type
exp_kind = HasCallStack => TCvSubst -> Type -> Type
TCvSubst -> Type -> Type
substTy TCvSubst
subst (Type -> Type) -> Type -> Type
forall a b. (a -> b) -> a -> b
$ TyBinder -> Type
tyBinderType TyBinder
ki_binder
                ; Type
arg' <- SDoc -> TcM Type -> TcM Type
forall a. SDoc -> TcM a -> TcM a
addErrCtxt (GenLocated SrcSpanAnnA (HsType GhcRn)
-> GenLocated SrcSpanAnnA (HsType GhcRn) -> Arity -> SDoc
forall fun arg.
(Outputable fun, Outputable arg) =>
fun -> arg -> Arity -> SDoc
funAppCtxt GenLocated SrcSpanAnnA (HsType GhcRn)
LHsType GhcRn
orig_hs_ty GenLocated SrcSpanAnnA (HsType GhcRn)
arg Arity
n) (TcM Type -> TcM Type) -> TcM Type -> TcM Type
forall a b. (a -> b) -> a -> b
$
                          TcTyMode -> LHsType GhcRn -> Type -> TcM Type
tc_lhs_type TcTyMode
mode GenLocated SrcSpanAnnA (HsType GhcRn)
LHsType GhcRn
arg Type
exp_kind
                ; String -> SDoc -> TcM ()
traceTc String
"tcInferTyApps (vis normal app) 2" (Type -> SDoc
forall a. Outputable a => a -> SDoc
ppr Type
exp_kind)
                ; (TCvSubst
subst', Type
fun') <- TCvSubst -> Type -> TyBinder -> Type -> TcM (TCvSubst, Type)
mkAppTyM TCvSubst
subst Type
fun TyBinder
ki_binder Type
arg'
                ; Arity
-> Type -> TCvSubst -> Type -> HsTyPats GhcRn -> TcM (Type, Type)
go (Arity
nArity -> Arity -> Arity
forall a. Num a => a -> a -> a
+Arity
1) Type
fun' TCvSubst
subst' Type
inner_ki [HsArg
   (GenLocated SrcSpanAnnA (HsType GhcRn))
   (GenLocated SrcSpanAnnA (HsType GhcRn))]
HsTyPats GhcRn
args }

          -- no binder; try applying the substitution, or infer another arrow in fun kind
      (HsValArg GenLocated SrcSpanAnnA (HsType GhcRn)
_ : [HsArg
   (GenLocated SrcSpanAnnA (HsType GhcRn))
   (GenLocated SrcSpanAnnA (HsType GhcRn))]
_, Maybe (TyBinder, Type)
Nothing)
        -> TcM (Type, Type) -> TcM (Type, Type)
try_again_after_substing_or (TcM (Type, Type) -> TcM (Type, Type))
-> TcM (Type, Type) -> TcM (Type, Type)
forall a b. (a -> b) -> a -> b
$
           do { let arrows_needed :: Arity
arrows_needed = [HsArg
   (GenLocated SrcSpanAnnA (HsType GhcRn))
   (GenLocated SrcSpanAnnA (HsType GhcRn))]
-> Arity
forall tm ty. [HsArg tm ty] -> Arity
n_initial_val_args [HsArg
   (GenLocated SrcSpanAnnA (HsType GhcRn))
   (GenLocated SrcSpanAnnA (HsType GhcRn))]
HsTyPats GhcRn
all_args
              ; Coercion
co <- GenLocated SrcSpanAnnA (HsType GhcRn)
-> Arity -> Type -> TcM Coercion
forall fun. Outputable fun => fun -> Arity -> Type -> TcM Coercion
matchExpectedFunKind GenLocated SrcSpanAnnA (HsType GhcRn)
LHsType GhcRn
hs_ty Arity
arrows_needed Type
substed_fun_ki

              ; Type
fun' <- Type -> TcM Type
zonkTcType (Type
fun Type -> Coercion -> Type
`mkTcCastTy` Coercion
co)
                     -- This zonk is essential, to expose the fruits
                     -- of matchExpectedFunKind to the 'go' loop

              ; String -> SDoc -> TcM ()
traceTc String
"tcInferTyApps (no binder)" (SDoc -> TcM ()) -> SDoc -> TcM ()
forall a b. (a -> b) -> a -> b
$
                   [SDoc] -> SDoc
vcat [ Type -> SDoc
forall a. Outputable a => a -> SDoc
ppr Type
fun SDoc -> SDoc -> SDoc
<+> SDoc
dcolon SDoc -> SDoc -> SDoc
<+> Type -> SDoc
forall a. Outputable a => a -> SDoc
ppr Type
fun_ki
                        , Arity -> SDoc
forall a. Outputable a => a -> SDoc
ppr Arity
arrows_needed
                        , Coercion -> SDoc
forall a. Outputable a => a -> SDoc
ppr Coercion
co
                        , Type -> SDoc
forall a. Outputable a => a -> SDoc
ppr Type
fun' SDoc -> SDoc -> SDoc
<+> SDoc
dcolon SDoc -> SDoc -> SDoc
<+> Type -> SDoc
forall a. Outputable a => a -> SDoc
ppr (HasDebugCallStack => Type -> Type
Type -> Type
tcTypeKind Type
fun')]
              ; Arity
-> Type
-> [HsArg
      (GenLocated SrcSpanAnnA (HsType GhcRn))
      (GenLocated SrcSpanAnnA (HsType GhcRn))]
-> TcM (Type, Type)
go_init Arity
n Type
fun' [HsArg
   (GenLocated SrcSpanAnnA (HsType GhcRn))
   (GenLocated SrcSpanAnnA (HsType GhcRn))]
HsTyPats GhcRn
all_args }
                -- Use go_init to establish go's INVARIANT
      where
        instantiate :: TyBinder -> Type -> TcM (Type, Type)
instantiate TyBinder
ki_binder Type
inner_ki
          = do { String -> SDoc -> TcM ()
traceTc String
"tcInferTyApps (need to instantiate)"
                         ([SDoc] -> SDoc
vcat [ TyBinder -> SDoc
forall a. Outputable a => a -> SDoc
ppr TyBinder
ki_binder, TCvSubst -> SDoc
forall a. Outputable a => a -> SDoc
ppr TCvSubst
subst])
               ; (TCvSubst
subst', Type
arg') <- TCvSubst -> TyBinder -> TcM (TCvSubst, Type)
tcInstInvisibleTyBinder TCvSubst
subst TyBinder
ki_binder
               ; Arity
-> Type -> TCvSubst -> Type -> HsTyPats GhcRn -> TcM (Type, Type)
go Arity
n (Type -> Type -> Type
mkAppTy Type
fun Type
arg') TCvSubst
subst' Type
inner_ki HsTyPats GhcRn
all_args }
                 -- Because tcInvisibleTyBinder instantiate ki_binder,
                 -- the kind of arg' will have the same shape as the kind
                 -- of ki_binder.  So we don't need mkAppTyM here.

        try_again_after_substing_or :: TcM (Type, Type) -> TcM (Type, Type)
try_again_after_substing_or TcM (Type, Type)
fallthrough
          | Bool -> Bool
not (TCvSubst -> Bool
isEmptyTCvSubst TCvSubst
subst)
          = Arity
-> Type -> TCvSubst -> Type -> HsTyPats GhcRn -> TcM (Type, Type)
go Arity
n Type
fun TCvSubst
zapped_subst Type
substed_fun_ki HsTyPats GhcRn
all_args
          | Bool
otherwise
          = TcM (Type, Type)
fallthrough

        zapped_subst :: TCvSubst
zapped_subst   = TCvSubst -> TCvSubst
zapTCvSubst TCvSubst
subst
        substed_fun_ki :: Type
substed_fun_ki = HasCallStack => TCvSubst -> Type -> Type
TCvSubst -> Type -> Type
substTy TCvSubst
subst Type
fun_ki
        hs_ty :: LHsType GhcRn
hs_ty          = LHsType GhcRn -> HsTyPats GhcRn -> LHsType GhcRn
appTypeToArg LHsType GhcRn
orig_hs_ty (Arity
-> [HsArg
      (GenLocated SrcSpanAnnA (HsType GhcRn))
      (GenLocated SrcSpanAnnA (HsType GhcRn))]
-> [HsArg
      (GenLocated SrcSpanAnnA (HsType GhcRn))
      (GenLocated SrcSpanAnnA (HsType GhcRn))]
forall a. Arity -> [a] -> [a]
take (Arity
nArity -> Arity -> Arity
forall a. Num a => a -> a -> a
-Arity
1) [HsArg
   (GenLocated SrcSpanAnnA (HsType GhcRn))
   (GenLocated SrcSpanAnnA (HsType GhcRn))]
HsTyPats GhcRn
orig_hs_args)

    n_initial_val_args :: [HsArg tm ty] -> Arity
    -- Count how many leading HsValArgs we have
    n_initial_val_args :: forall tm ty. [HsArg tm ty] -> Arity
n_initial_val_args (HsValArg {} : [HsArg tm ty]
args) = Arity
1 Arity -> Arity -> Arity
forall a. Num a => a -> a -> a
+ [HsArg tm ty] -> Arity
forall tm ty. [HsArg tm ty] -> Arity
n_initial_val_args [HsArg tm ty]
args
    n_initial_val_args (HsArgPar {} : [HsArg tm ty]
args) = [HsArg tm ty] -> Arity
forall tm ty. [HsArg tm ty] -> Arity
n_initial_val_args [HsArg tm ty]
args
    n_initial_val_args [HsArg tm ty]
_                    = Arity
0

    ty_app_err :: a -> a -> TcRn a
ty_app_err a
arg a
ty
      = SDoc -> TcRn a
forall a. SDoc -> TcM a
failWith (SDoc -> TcRn a) -> SDoc -> TcRn a
forall a b. (a -> b) -> a -> b
$ String -> SDoc
text String
"Cannot apply function of kind" SDoc -> SDoc -> SDoc
<+> SDoc -> SDoc
quotes (a -> SDoc
forall a. Outputable a => a -> SDoc
ppr a
ty)
                SDoc -> SDoc -> SDoc
$$ String -> SDoc
text String
"to visible kind argument" SDoc -> SDoc -> SDoc
<+> SDoc -> SDoc
quotes (a -> SDoc
forall a. Outputable a => a -> SDoc
ppr a
arg)


mkAppTyM :: TCvSubst
         -> TcType -> TyCoBinder    -- fun, plus its top-level binder
         -> TcType                  -- arg
         -> TcM (TCvSubst, TcType)  -- Extended subst, plus (fun arg)
-- Precondition: the application (fun arg) is well-kinded after zonking
--               That is, the application makes sense
--
-- Precondition: for (mkAppTyM subst fun bndr arg)
--       tcTypeKind fun  =  Pi bndr. body
--  That is, fun always has a ForAllTy or FunTy at the top
--           and 'bndr' is fun's pi-binder
--
-- Postcondition: if fun and arg satisfy (PKTI), the purely-kinded type
--                invariant, then so does the result type (fun arg)
--
-- We do not require that
--    tcTypeKind arg = tyVarKind (binderVar bndr)
-- This must be true after zonking (precondition 1), but it's not
-- required for the (PKTI).
mkAppTyM :: TCvSubst -> Type -> TyBinder -> Type -> TcM (TCvSubst, Type)
mkAppTyM TCvSubst
subst Type
fun TyBinder
ki_binder Type
arg
  | -- See Note [mkAppTyM]: Nasty case 2
    TyConApp TyCon
tc [Type]
args <- Type
fun
  , TyCon -> Bool
isTypeSynonymTyCon TyCon
tc
  , [Type]
args [Type] -> Arity -> Bool
forall a. [a] -> Arity -> Bool
`lengthIs` (TyCon -> Arity
tyConArity TyCon
tc Arity -> Arity -> Arity
forall a. Num a => a -> a -> a
- Arity
1)
  , (TyVar -> Bool) -> [TyVar] -> Bool
forall (t :: * -> *) a. Foldable t => (a -> Bool) -> t a -> Bool
any TyVar -> Bool
isTrickyTvBinder (TyCon -> [TyVar]
tyConTyVars TyCon
tc) -- We could cache this in the synonym
  = do { Type
arg'  <- Type -> TcM Type
zonkTcType  Type
arg
       ; [Type]
args' <- [Type] -> TcM [Type]
zonkTcTypes [Type]
args
       ; let subst' :: TCvSubst
subst' = case TyBinder
ki_binder of
                        Anon {}           -> TCvSubst
subst
                        Named (Bndr TyVar
tv ArgFlag
_) -> TCvSubst -> TyVar -> Type -> TCvSubst
extendTvSubstAndInScope TCvSubst
subst TyVar
tv Type
arg'
       ; (TCvSubst, Type) -> TcM (TCvSubst, Type)
forall (m :: * -> *) a. Monad m => a -> m a
return (TCvSubst
subst', TyCon -> [Type] -> Type
mkTyConApp TyCon
tc ([Type]
args' [Type] -> [Type] -> [Type]
forall a. [a] -> [a] -> [a]
++ [Type
arg'])) }


mkAppTyM TCvSubst
subst Type
fun (Anon {}) Type
arg
   = (TCvSubst, Type) -> TcM (TCvSubst, Type)
forall (m :: * -> *) a. Monad m => a -> m a
return (TCvSubst
subst, Type -> Type -> Type
mk_app_ty Type
fun Type
arg)

mkAppTyM TCvSubst
subst Type
fun (Named (Bndr TyVar
tv ArgFlag
_)) Type
arg
  = do { Type
arg' <- if TyVar -> Bool
isTrickyTvBinder TyVar
tv
                 then -- See Note [mkAppTyM]: Nasty case 1
                      Type -> TcM Type
zonkTcType Type
arg
                 else Type -> TcM Type
forall (m :: * -> *) a. Monad m => a -> m a
return     Type
arg
       ; (TCvSubst, Type) -> TcM (TCvSubst, Type)
forall (m :: * -> *) a. Monad m => a -> m a
return ( TCvSubst -> TyVar -> Type -> TCvSubst
extendTvSubstAndInScope TCvSubst
subst TyVar
tv Type
arg'
                , Type -> Type -> Type
mk_app_ty Type
fun Type
arg' ) }

mk_app_ty :: TcType -> TcType -> TcType
-- This function just adds an ASSERT for mkAppTyM's precondition
mk_app_ty :: Type -> Type -> Type
mk_app_ty Type
fun Type
arg
  = ASSERT2( isPiTy fun_kind
           ,  ppr fun <+> dcolon <+> ppr fun_kind $$ ppr arg )
    Type -> Type -> Type
mkAppTy Type
fun Type
arg
  where
    fun_kind :: Type
fun_kind = HasDebugCallStack => Type -> Type
Type -> Type
tcTypeKind Type
fun

isTrickyTvBinder :: TcTyVar -> Bool
-- NB: isTrickyTvBinder is just an optimisation
-- It would be absolutely sound to return True always
isTrickyTvBinder :: TyVar -> Bool
isTrickyTvBinder TyVar
tv = Type -> Bool
isPiTy (TyVar -> Type
tyVarKind TyVar
tv)

{- Note [The Purely Kinded Type Invariant (PKTI)]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
During type inference, we maintain this invariant

 (PKTI) It is legal to call 'tcTypeKind' on any Type ty,
        on any sub-term of ty, /without/ zonking ty

        Moreover, any such returned kind
        will itself satisfy (PKTI)

By "legal to call tcTypeKind" we mean "tcTypeKind will not crash".
The way in which tcTypeKind can crash is in applications
    (a t1 t2 .. tn)
if 'a' is a type variable whose kind doesn't have enough arrows
or foralls.  (The crash is in piResultTys.)

The loop in tcInferTyApps has to be very careful to maintain the (PKTI).
For example, suppose
    kappa is a unification variable
    We have already unified kappa := Type
      yielding    co :: Refl (Type -> Type)
    a :: kappa
then consider the type
    (a Int)
If we call tcTypeKind on that, we'll crash, because the (un-zonked)
kind of 'a' is just kappa, not an arrow kind.  So we must zonk first.

So the type inference engine is very careful when building applications.
This happens in tcInferTyApps. Suppose we are kind-checking the type (a Int),
where (a :: kappa).  Then in tcInferApps we'll run out of binders on
a's kind, so we'll call matchExpectedFunKind, and unify
   kappa := kappa1 -> kappa2,  with evidence co :: kappa ~ (kappa1 ~ kappa2)
At this point we must zonk the function type to expose the arrrow, so
that (a Int) will satisfy (PKTI).

The absence of this caused #14174 and #14520.

The calls to mkAppTyM is the other place we are very careful.

Note [mkAppTyM]
~~~~~~~~~~~~~~~
mkAppTyM is trying to guarantee the Purely Kinded Type Invariant
(PKTI) for its result type (fun arg).  There are two ways it can go wrong:

* Nasty case 1: forall types (polykinds/T14174a)
    T :: forall (p :: *->*). p Int -> p Bool
  Now kind-check (T x), where x::kappa.
  Well, T and x both satisfy the PKTI, but
     T x :: x Int -> x Bool
  and (x Int) does /not/ satisfy the PKTI.

* Nasty case 2: type synonyms
    type S f a = f a
  Even though (S ff aa) would satisfy the (PKTI) if S was a data type
  (i.e. nasty case 1 is dealt with), it might still not satisfy (PKTI)
  if S is a type synonym, because the /expansion/ of (S ff aa) is
  (ff aa), and /that/ does not satisfy (PKTI).  E.g. perhaps
  (ff :: kappa), where 'kappa' has already been unified with (*->*).

  We check for nasty case 2 on the final argument of a type synonym.

Notice that in both cases the trickiness only happens if the
bound variable has a pi-type.  Hence isTrickyTvBinder.
-}


saturateFamApp :: TcType -> TcKind -> TcM (TcType, TcKind)
-- Precondition for (saturateFamApp ty kind):
--     tcTypeKind ty = kind
--
-- If 'ty' is an unsaturated family application with trailing
-- invisible arguments, instantiate them.
-- See Note [saturateFamApp]

saturateFamApp :: Type -> Type -> TcM (Type, Type)
saturateFamApp Type
ty Type
kind
  | Just (TyCon
tc, [Type]
args) <- HasCallStack => Type -> Maybe (TyCon, [Type])
Type -> Maybe (TyCon, [Type])
tcSplitTyConApp_maybe Type
ty
  , TyCon -> Bool
mustBeSaturated TyCon
tc
  , let n_to_inst :: Arity
n_to_inst = TyCon -> Arity
tyConArity TyCon
tc Arity -> Arity -> Arity
forall a. Num a => a -> a -> a
- [Type] -> Arity
forall (t :: * -> *) a. Foldable t => t a -> Arity
length [Type]
args
  = do { ([Type]
extra_args, Type
ki') <- Arity -> Type -> TcM ([Type], Type)
tcInstInvisibleTyBindersN Arity
n_to_inst Type
kind
       ; (Type, Type) -> TcM (Type, Type)
forall (m :: * -> *) a. Monad m => a -> m a
return (Type
ty Type -> [Type] -> Type
`mkTcAppTys` [Type]
extra_args, Type
ki') }
  | Bool
otherwise
  = (Type, Type) -> TcM (Type, Type)
forall (m :: * -> *) a. Monad m => a -> m a
return (Type
ty, Type
kind)

{- Note [saturateFamApp]
~~~~~~~~~~~~~~~~~~~~~~~~
Consider
   type family F :: Either j k
   type instance F @Type = Right Maybe
   type instance F @Type = Right Either```

Then F :: forall {j,k}. Either j k

The two type instances do a visible kind application that instantiates
'j' but not 'k'.  But we want to end up with instances that look like
  type instance F @Type @(*->*) = Right @Type @(*->*) Maybe

so that F has arity 2.  We must instantiate that trailing invisible
binder. In general, Invisible binders precede Specified and Required,
so this is only going to bite for apparently-nullary families.

Note that
  type family F2 :: forall k. k -> *
is quite different and really does have arity 0.

It's not just type instances where we need to saturate those
unsaturated arguments: see #11246.  Hence doing this in tcInferApps.
-}

appTypeToArg :: LHsType GhcRn -> [LHsTypeArg GhcRn] -> LHsType GhcRn
appTypeToArg :: LHsType GhcRn -> HsTyPats GhcRn -> LHsType GhcRn
appTypeToArg LHsType GhcRn
f []                       = LHsType GhcRn
f
appTypeToArg LHsType GhcRn
f (HsValArg LHsType GhcRn
arg    : HsTyPats GhcRn
args) = LHsType GhcRn -> HsTyPats GhcRn -> LHsType GhcRn
appTypeToArg (LHsType GhcRn -> LHsType GhcRn -> LHsType GhcRn
forall (p :: Pass).
LHsType (GhcPass p) -> LHsType (GhcPass p) -> LHsType (GhcPass p)
mkHsAppTy LHsType GhcRn
f LHsType GhcRn
arg) HsTyPats GhcRn
args
appTypeToArg LHsType GhcRn
f (HsArgPar SrcSpan
_      : HsTyPats GhcRn
args) = LHsType GhcRn -> HsTyPats GhcRn -> LHsType GhcRn
appTypeToArg LHsType GhcRn
f                 HsTyPats GhcRn
args
appTypeToArg LHsType GhcRn
f (HsTypeArg SrcSpan
l LHsType GhcRn
arg : HsTyPats GhcRn
args)
  = LHsType GhcRn -> HsTyPats GhcRn -> LHsType GhcRn
appTypeToArg (XAppKindTy GhcRn -> LHsType GhcRn -> LHsType GhcRn -> LHsType GhcRn
forall (p :: Pass).
XAppKindTy (GhcPass p)
-> LHsType (GhcPass p)
-> LHsType (GhcPass p)
-> LHsType (GhcPass p)
mkHsAppKindTy SrcSpan
XAppKindTy GhcRn
l LHsType GhcRn
f LHsType GhcRn
arg) HsTyPats GhcRn
args


{- *********************************************************************
*                                                                      *
                checkExpectedKind
*                                                                      *
********************************************************************* -}

-- | This instantiates invisible arguments for the type being checked if it must
-- be saturated and is not yet saturated. It then calls and uses the result
-- from checkExpectedKindX to build the final type
checkExpectedKind :: HasDebugCallStack
                  => HsType GhcRn       -- ^ type we're checking (for printing)
                  -> TcType             -- ^ type we're checking
                  -> TcKind             -- ^ the known kind of that type
                  -> TcKind             -- ^ the expected kind
                  -> TcM TcType
-- Just a convenience wrapper to save calls to 'ppr'
checkExpectedKind :: HasDebugCallStack =>
HsType GhcRn -> Type -> Type -> Type -> TcM Type
checkExpectedKind HsType GhcRn
hs_ty Type
ty Type
act_kind Type
exp_kind
  = do { String -> SDoc -> TcM ()
traceTc String
"checkExpectedKind" (Type -> SDoc
forall a. Outputable a => a -> SDoc
ppr Type
ty SDoc -> SDoc -> SDoc
$$ Type -> SDoc
forall a. Outputable a => a -> SDoc
ppr Type
act_kind)

       ; ([Type]
new_args, Type
act_kind') <- Arity -> Type -> TcM ([Type], Type)
tcInstInvisibleTyBindersN Arity
n_to_inst Type
act_kind

       ; let origin :: CtOrigin
origin = TypeEqOrigin { uo_actual :: Type
uo_actual   = Type
act_kind'
                                   , uo_expected :: Type
uo_expected = Type
exp_kind
                                   , uo_thing :: Maybe SDoc
uo_thing    = SDoc -> Maybe SDoc
forall a. a -> Maybe a
Just (HsType GhcRn -> SDoc
forall a. Outputable a => a -> SDoc
ppr HsType GhcRn
hs_ty)
                                   , uo_visible :: Bool
uo_visible  = Bool
True } -- the hs_ty is visible

       ; String -> SDoc -> TcM ()
traceTc String
"checkExpectedKindX" (SDoc -> TcM ()) -> SDoc -> TcM ()
forall a b. (a -> b) -> a -> b
$
         [SDoc] -> SDoc
vcat [ HsType GhcRn -> SDoc
forall a. Outputable a => a -> SDoc
ppr HsType GhcRn
hs_ty
              , String -> SDoc
text String
"act_kind':" SDoc -> SDoc -> SDoc
<+> Type -> SDoc
forall a. Outputable a => a -> SDoc
ppr Type
act_kind'
              , String -> SDoc
text String
"exp_kind:" SDoc -> SDoc -> SDoc
<+> Type -> SDoc
forall a. Outputable a => a -> SDoc
ppr Type
exp_kind ]

       ; let res_ty :: Type
res_ty = Type
ty Type -> [Type] -> Type
`mkTcAppTys` [Type]
new_args

       ; if Type
act_kind' HasDebugCallStack => Type -> Type -> Bool
Type -> Type -> Bool
`tcEqType` Type
exp_kind
         then Type -> TcM Type
forall (m :: * -> *) a. Monad m => a -> m a
return Type
res_ty  -- This is very common
         else do { Coercion
co_k <- TypeOrKind -> CtOrigin -> Type -> Type -> TcM Coercion
uType TypeOrKind
KindLevel CtOrigin
origin Type
act_kind' Type
exp_kind
                 ; String -> SDoc -> TcM ()
traceTc String
"checkExpectedKind" ([SDoc] -> SDoc
vcat [ Type -> SDoc
forall a. Outputable a => a -> SDoc
ppr Type
act_kind
                                                     , Type -> SDoc
forall a. Outputable a => a -> SDoc
ppr Type
exp_kind
                                                     , Coercion -> SDoc
forall a. Outputable a => a -> SDoc
ppr Coercion
co_k ])
                ; Type -> TcM Type
forall (m :: * -> *) a. Monad m => a -> m a
return (Type
res_ty Type -> Coercion -> Type
`mkTcCastTy` Coercion
co_k) } }
    where
      -- We need to make sure that both kinds have the same number of implicit
      -- foralls out front. If the actual kind has more, instantiate accordingly.
      -- Otherwise, just pass the type & kind through: the errors are caught
      -- in unifyType.
      n_exp_invis_bndrs :: Arity
n_exp_invis_bndrs = Type -> Arity
invisibleTyBndrCount Type
exp_kind
      n_act_invis_bndrs :: Arity
n_act_invis_bndrs = Type -> Arity
invisibleTyBndrCount Type
act_kind
      n_to_inst :: Arity
n_to_inst         = Arity
n_act_invis_bndrs Arity -> Arity -> Arity
forall a. Num a => a -> a -> a
- Arity
n_exp_invis_bndrs

---------------------------

tcHsContext :: Maybe (LHsContext GhcRn) -> TcM [PredType]
tcHsContext :: Maybe (LHsContext GhcRn) -> TcM [Type]
tcHsContext Maybe (LHsContext GhcRn)
cxt = TcTyMode -> Maybe (LHsContext GhcRn) -> TcM [Type]
tc_hs_context TcTyMode
typeLevelMode Maybe (LHsContext GhcRn)
cxt

tcLHsPredType :: LHsType GhcRn -> TcM PredType
tcLHsPredType :: LHsType GhcRn -> TcM Type
tcLHsPredType LHsType GhcRn
pred = TcTyMode -> LHsType GhcRn -> TcM Type
tc_lhs_pred TcTyMode
typeLevelMode LHsType GhcRn
pred

tc_hs_context :: TcTyMode -> Maybe (LHsContext GhcRn) -> TcM [PredType]
tc_hs_context :: TcTyMode -> Maybe (LHsContext GhcRn) -> TcM [Type]
tc_hs_context TcTyMode
_ Maybe (LHsContext GhcRn)
Nothing = [Type] -> TcM [Type]
forall (m :: * -> *) a. Monad m => a -> m a
return []
tc_hs_context TcTyMode
mode (Just LHsContext GhcRn
ctxt) = (GenLocated SrcSpanAnnA (HsType GhcRn) -> TcM Type)
-> [GenLocated SrcSpanAnnA (HsType GhcRn)] -> TcM [Type]
forall (t :: * -> *) (m :: * -> *) a b.
(Traversable t, Monad m) =>
(a -> m b) -> t a -> m (t b)
mapM (TcTyMode -> LHsType GhcRn -> TcM Type
tc_lhs_pred TcTyMode
mode) (GenLocated SrcSpanAnnC [GenLocated SrcSpanAnnA (HsType GhcRn)]
-> [GenLocated SrcSpanAnnA (HsType GhcRn)]
forall l e. GenLocated l e -> e
unLoc GenLocated SrcSpanAnnC [GenLocated SrcSpanAnnA (HsType GhcRn)]
LHsContext GhcRn
ctxt)

tc_lhs_pred :: TcTyMode -> LHsType GhcRn -> TcM PredType
tc_lhs_pred :: TcTyMode -> LHsType GhcRn -> TcM Type
tc_lhs_pred TcTyMode
mode LHsType GhcRn
pred = TcTyMode -> LHsType GhcRn -> Type -> TcM Type
tc_lhs_type TcTyMode
mode LHsType GhcRn
pred Type
constraintKind

---------------------------
tcTyVar :: TcTyMode -> Name -> TcM (TcType, TcKind)
-- See Note [Type checking recursive type and class declarations]
-- in GHC.Tc.TyCl
-- This does not instantiate. See Note [Do not always instantiate eagerly in types]
tcTyVar :: TcTyMode -> Name -> TcM (Type, Type)
tcTyVar TcTyMode
mode Name
name         -- Could be a tyvar, a tycon, or a datacon
  = do { String -> SDoc -> TcM ()
traceTc String
"lk1" (Name -> SDoc
forall a. Outputable a => a -> SDoc
ppr Name
name)
       ; TcTyThing
thing <- Name -> TcM TcTyThing
tcLookup Name
name
       ; case TcTyThing
thing of
           ATyVar Name
_ TyVar
tv -> (Type, Type) -> TcM (Type, Type)
forall (m :: * -> *) a. Monad m => a -> m a
return (TyVar -> Type
mkTyVarTy TyVar
tv, TyVar -> Type
tyVarKind TyVar
tv)

           -- See Note [Recursion through the kinds]
           ATcTyCon TyCon
tc_tc
             -> do { TyCon -> TcM ()
check_tc TyCon
tc_tc
                   ; (Type, Type) -> TcM (Type, Type)
forall (m :: * -> *) a. Monad m => a -> m a
return (TyCon -> Type
mkTyConTy TyCon
tc_tc, TyCon -> Type
tyConKind TyCon
tc_tc) }

           AGlobal (ATyCon TyCon
tc)
             -> do { TyCon -> TcM ()
check_tc TyCon
tc
                   ; (Type, Type) -> TcM (Type, Type)
forall (m :: * -> *) a. Monad m => a -> m a
return (TyCon -> Type
mkTyConTy TyCon
tc, TyCon -> Type
tyConKind TyCon
tc) }

           AGlobal (AConLike (RealDataCon DataCon
dc))
             -> do { Bool
data_kinds <- Extension -> TcRnIf TcGblEnv TcLclEnv Bool
forall gbl lcl. Extension -> TcRnIf gbl lcl Bool
xoptM Extension
LangExt.DataKinds
                   ; Bool -> TcM () -> TcM ()
forall (f :: * -> *). Applicative f => Bool -> f () -> f ()
unless (Bool
data_kinds Bool -> Bool -> Bool
|| DataCon -> Bool
specialPromotedDc DataCon
dc) (TcM () -> TcM ()) -> TcM () -> TcM ()
forall a b. (a -> b) -> a -> b
$
                       Name -> PromotionErr -> TcM ()
forall a. Name -> PromotionErr -> TcM a
promotionErr Name
name PromotionErr
NoDataKindsDC
                   ; Bool -> TcM () -> TcM ()
forall (f :: * -> *). Applicative f => Bool -> f () -> f ()
when (TyCon -> Bool
isFamInstTyCon (DataCon -> TyCon
dataConTyCon DataCon
dc)) (TcM () -> TcM ()) -> TcM () -> TcM ()
forall a b. (a -> b) -> a -> b
$
                       -- see #15245
                       Name -> PromotionErr -> TcM ()
forall a. Name -> PromotionErr -> TcM a
promotionErr Name
name PromotionErr
FamDataConPE
                   ; let ([TyVar]
_, [TyVar]
_, [EqSpec]
_, [Type]
theta, [Scaled Type]
_, Type
_) = DataCon
-> ([TyVar], [TyVar], [EqSpec], [Type], [Scaled Type], Type)
dataConFullSig DataCon
dc
                   ; String -> SDoc -> TcM ()
traceTc String
"tcTyVar" (DataCon -> SDoc
forall a. Outputable a => a -> SDoc
ppr DataCon
dc SDoc -> SDoc -> SDoc
<+> [Type] -> SDoc
forall a. Outputable a => a -> SDoc
ppr [Type]
theta SDoc -> SDoc -> SDoc
$$ Maybe Type -> SDoc
forall a. Outputable a => a -> SDoc
ppr ([Type] -> Maybe Type
dc_theta_illegal_constraint [Type]
theta))
                   ; case [Type] -> Maybe Type
dc_theta_illegal_constraint [Type]
theta of
                       Just Type
pred -> Name -> PromotionErr -> TcM ()
forall a. Name -> PromotionErr -> TcM a
promotionErr Name
name (PromotionErr -> TcM ()) -> PromotionErr -> TcM ()
forall a b. (a -> b) -> a -> b
$
                                    Type -> PromotionErr
ConstrainedDataConPE Type
pred
                       Maybe Type
Nothing   -> () -> TcM ()
forall (f :: * -> *) a. Applicative f => a -> f a
pure ()
                   ; let tc :: TyCon
tc = DataCon -> TyCon
promoteDataCon DataCon
dc
                   ; (Type, Type) -> TcM (Type, Type)
forall (m :: * -> *) a. Monad m => a -> m a
return (TyCon -> [Type] -> Type
mkTyConApp TyCon
tc [], TyCon -> Type
tyConKind TyCon
tc) }

           APromotionErr PromotionErr
err -> Name -> PromotionErr -> TcM (Type, Type)
forall a. Name -> PromotionErr -> TcM a
promotionErr Name
name PromotionErr
err

           TcTyThing
_  -> String -> TcTyThing -> Name -> TcM (Type, Type)
forall a. String -> TcTyThing -> Name -> TcM a
wrongThingErr String
"type" TcTyThing
thing Name
name }
  where
    check_tc :: TyCon -> TcM ()
    check_tc :: TyCon -> TcM ()
check_tc TyCon
tc = do { Bool
data_kinds   <- Extension -> TcRnIf TcGblEnv TcLclEnv Bool
forall gbl lcl. Extension -> TcRnIf gbl lcl Bool
xoptM Extension
LangExt.DataKinds
                     ; Bool -> TcM () -> TcM ()
forall (f :: * -> *). Applicative f => Bool -> f () -> f ()
unless (TypeOrKind -> Bool
isTypeLevel (TcTyMode -> TypeOrKind
mode_tyki TcTyMode
mode) Bool -> Bool -> Bool
||
                               Bool
data_kinds Bool -> Bool -> Bool
||
                               TyCon -> Bool
isKindTyCon TyCon
tc) (TcM () -> TcM ()) -> TcM () -> TcM ()
forall a b. (a -> b) -> a -> b
$
                       Name -> PromotionErr -> TcM ()
forall a. Name -> PromotionErr -> TcM a
promotionErr Name
name PromotionErr
NoDataKindsTC }

    -- We cannot promote a data constructor with a context that contains
    -- constraints other than equalities, so error if we find one.
    -- See Note [Constraints in kinds] in GHC.Core.TyCo.Rep
    dc_theta_illegal_constraint :: ThetaType -> Maybe PredType
    dc_theta_illegal_constraint :: [Type] -> Maybe Type
dc_theta_illegal_constraint = (Type -> Bool) -> [Type] -> Maybe Type
forall (t :: * -> *) a. Foldable t => (a -> Bool) -> t a -> Maybe a
find (Bool -> Bool
not (Bool -> Bool) -> (Type -> Bool) -> Type -> Bool
forall b c a. (b -> c) -> (a -> b) -> a -> c
. Type -> Bool
isEqPred)

{-
Note [Recursion through the kinds]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Consider these examples

Ticket #11554:
  data P (x :: k) = Q
  data A :: Type where
    MkA :: forall (a :: A). P a -> A

Ticket #12174
  data V a
  data T = forall (a :: T). MkT (V a)

The type is recursive (which is fine) but it is recursive /through the
kinds/.  In earlier versions of GHC this caused a loop in the compiler
(to do with knot-tying) but there is nothing fundamentally wrong with
the code (kinds are types, and the recursive declarations are OK). But
it's hard to distinguish "recursion through the kinds" from "recursion
through the types". Consider this (also #11554):

  data PB k (x :: k) = Q
  data B :: Type where
    MkB :: P B a -> B

Here the occurrence of B is not obviously in a kind position.

So now GHC allows all these programs.  #12081 and #15942 are other
examples.

Note [Body kind of a HsForAllTy]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
The body of a forall is usually a type, but in principle
there's no reason to prohibit *unlifted* types.
In fact, GHC can itself construct a function with an
unboxed tuple inside a for-all (via CPR analysis; see
typecheck/should_compile/tc170).

Moreover in instance heads we get forall-types with
kind Constraint.

It's tempting to check that the body kind is either * or #. But this is
wrong. For example:

  class C a b
  newtype N = Mk Foo deriving (C a)

We're doing newtype-deriving for C. But notice how `a` isn't in scope in
the predicate `C a`. So we quantify, yielding `forall a. C a` even though
`C a` has kind `* -> Constraint`. The `forall a. C a` is a bit cheeky, but
convenient. Bottom line: don't check for * or # here.

Note [Body kind of a HsQualTy]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
If ctxt is non-empty, the HsQualTy really is a /function/, so the
kind of the result really is '*', and in that case the kind of the
body-type can be lifted or unlifted.

However, consider
    instance Eq a => Eq [a] where ...
or
    f :: (Eq a => Eq [a]) => blah
Here both body-kind of the HsQualTy is Constraint rather than *.
Rather crudely we tell the difference by looking at exp_kind. It's
very convenient to typecheck instance types like any other HsSigType.

Admittedly the '(Eq a => Eq [a]) => blah' case is erroneous, but it's
better to reject in checkValidType.  If we say that the body kind
should be '*' we risk getting TWO error messages, one saying that Eq
[a] doesn't have kind '*', and one saying that we need a Constraint to
the left of the outer (=>).

How do we figure out the right body kind?  Well, it's a bit of a
kludge: I just look at the expected kind.  If it's Constraint, we
must be in this instance situation context. It's a kludge because it
wouldn't work if any unification was involved to compute that result
kind -- but it isn't.  (The true way might be to use the 'mode'
parameter, but that seemed like a sledgehammer to crack a nut.)

Note [Inferring tuple kinds]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Give a tuple type (a,b,c), which the parser labels as HsBoxedOrConstraintTuple,
we try to figure out whether it's a tuple of kind * or Constraint.
  Step 1: look at the expected kind
  Step 2: infer argument kinds

If after Step 2 it's not clear from the arguments that it's
Constraint, then it must be *.  Once having decided that we re-check
the arguments to give good error messages in
  e.g.  (Maybe, Maybe)

Note that we will still fail to infer the correct kind in this case:

  type T a = ((a,a), D a)
  type family D :: Constraint -> Constraint

While kind checking T, we do not yet know the kind of D, so we will default the
kind of T to * -> *. It works if we annotate `a` with kind `Constraint`.

Note [Desugaring types]
~~~~~~~~~~~~~~~~~~~~~~~
The type desugarer is phase 2 of dealing with HsTypes.  Specifically:

  * It transforms from HsType to Type

  * It zonks any kinds.  The returned type should have no mutable kind
    or type variables (hence returning Type not TcType):
      - any unconstrained kind variables are defaulted to (Any *) just
        as in GHC.Tc.Utils.Zonk.
      - there are no mutable type variables because we are
        kind-checking a type
    Reason: the returned type may be put in a TyCon or DataCon where
    it will never subsequently be zonked.

You might worry about nested scopes:
        ..a:kappa in scope..
            let f :: forall b. T '[a,b] -> Int
In this case, f's type could have a mutable kind variable kappa in it;
and we might then default it to (Any *) when dealing with f's type
signature.  But we don't expect this to happen because we can't get a
lexically scoped type variable with a mutable kind variable in it.  A
delicate point, this.  If it becomes an issue we might need to
distinguish top-level from nested uses.

Moreover
  * it cannot fail,
  * it does no unifications
  * it does no validity checking, except for structural matters, such as
        (a) spurious ! annotations.
        (b) a class used as a type

Note [Kind of a type splice]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Consider these terms, each with TH type splice inside:
     [| e1 :: Maybe $(..blah..) |]
     [| e2 :: $(..blah..) |]
When kind-checking the type signature, we'll kind-check the splice
$(..blah..); we want to give it a kind that can fit in any context,
as if $(..blah..) :: forall k. k.

In the e1 example, the context of the splice fixes kappa to *.  But
in the e2 example, we'll desugar the type, zonking the kind unification
variables as we go.  When we encounter the unconstrained kappa, we
want to default it to '*', not to (Any *).

-}

addTypeCtxt :: LHsType GhcRn -> TcM a -> TcM a
        -- Wrap a context around only if we want to show that contexts.
        -- Omit invisible ones and ones user's won't grok
addTypeCtxt :: forall a. LHsType GhcRn -> TcM a -> TcM a
addTypeCtxt (L SrcSpanAnnA
_ (HsWildCardTy XWildCardTy GhcRn
_)) TcM a
thing = TcM a
thing   -- "In the type '_'" just isn't helpful.
addTypeCtxt (L SrcSpanAnnA
_ HsType GhcRn
ty) TcM a
thing
  = SDoc -> TcM a -> TcM a
forall a. SDoc -> TcM a -> TcM a
addErrCtxt SDoc
doc TcM a
thing
  where
    doc :: SDoc
doc = String -> SDoc
text String
"In the type" SDoc -> SDoc -> SDoc
<+> SDoc -> SDoc
quotes (HsType GhcRn -> SDoc
forall a. Outputable a => a -> SDoc
ppr HsType GhcRn
ty)


{- *********************************************************************
*                                                                      *
                Type-variable binders
*                                                                      *
********************************************************************* -}

bindNamedWildCardBinders :: [Name]
                         -> ([(Name, TcTyVar)] -> TcM a)
                         -> TcM a
-- Bring into scope the /named/ wildcard binders.  Remember that
-- plain wildcards _ are anonymous and dealt with by HsWildCardTy
-- Soe Note [The wildcard story for types] in GHC.Hs.Type
bindNamedWildCardBinders :: forall a. HsQTvsRn -> ([(Name, TyVar)] -> TcM a) -> TcM a
bindNamedWildCardBinders HsQTvsRn
wc_names [(Name, TyVar)] -> TcM a
thing_inside
  = do { [TyVar]
wcs <- (Name -> IOEnv (Env TcGblEnv TcLclEnv) TyVar)
-> HsQTvsRn -> TcM [TyVar]
forall (t :: * -> *) (m :: * -> *) a b.
(Traversable t, Monad m) =>
(a -> m b) -> t a -> m (t b)
mapM Name -> IOEnv (Env TcGblEnv TcLclEnv) TyVar
newNamedWildTyVar HsQTvsRn
wc_names
       ; let wc_prs :: [(Name, TyVar)]
wc_prs = HsQTvsRn
wc_names HsQTvsRn -> [TyVar] -> [(Name, TyVar)]
forall a b. [a] -> [b] -> [(a, b)]
`zip` [TyVar]
wcs
       ; [(Name, TyVar)] -> TcM a -> TcM a
forall r. [(Name, TyVar)] -> TcM r -> TcM r
tcExtendNameTyVarEnv [(Name, TyVar)]
wc_prs (TcM a -> TcM a) -> TcM a -> TcM a
forall a b. (a -> b) -> a -> b
$
         [(Name, TyVar)] -> TcM a
thing_inside [(Name, TyVar)]
wc_prs }

newNamedWildTyVar :: Name -> TcM TcTyVar
-- ^ New unification variable '_' for a wildcard
newNamedWildTyVar :: Name -> IOEnv (Env TcGblEnv TcLclEnv) TyVar
newNamedWildTyVar Name
_name   -- Currently ignoring the "_x" wildcard name used in the type
  = do { Type
kind <- TcM Type
newMetaKindVar
       ; TcTyVarDetails
details <- MetaInfo -> TcM TcTyVarDetails
newMetaDetails MetaInfo
TauTv
       ; Name
wc_name <- FastString -> TcM Name
newMetaTyVarName (String -> FastString
fsLit String
"w")   -- See Note [Wildcard names]
       ; let tyvar :: TyVar
tyvar = Name -> Type -> TcTyVarDetails -> TyVar
mkTcTyVar Name
wc_name Type
kind TcTyVarDetails
details
       ; String -> SDoc -> TcM ()
traceTc String
"newWildTyVar" (TyVar -> SDoc
forall a. Outputable a => a -> SDoc
ppr TyVar
tyvar)
       ; TyVar -> IOEnv (Env TcGblEnv TcLclEnv) TyVar
forall (m :: * -> *) a. Monad m => a -> m a
return TyVar
tyvar }

---------------------------
tcAnonWildCardOcc :: IsExtraConstraint
                  -> TcTyMode -> HsType GhcRn -> Kind -> TcM TcType
tcAnonWildCardOcc :: IsExtraConstraint -> TcTyMode -> HsType GhcRn -> Type -> TcM Type
tcAnonWildCardOcc IsExtraConstraint
is_extra (TcTyMode { mode_holes :: TcTyMode -> HoleInfo
mode_holes = Just (TcLevel
hole_lvl, HoleMode
hole_mode) })
                  HsType GhcRn
ty Type
exp_kind
    -- hole_lvl: see Note [Checking partial type signatures]
    --           esp the bullet on nested forall types
  = do { TcTyVarDetails
kv_details <- TcLevel -> TcM TcTyVarDetails
newTauTvDetailsAtLevel TcLevel
hole_lvl
       ; Name
kv_name    <- FastString -> TcM Name
newMetaTyVarName (String -> FastString
fsLit String
"k")
       ; TcTyVarDetails
wc_details <- TcLevel -> TcM TcTyVarDetails
newTauTvDetailsAtLevel TcLevel
hole_lvl
       ; Name
wc_name    <- FastString -> TcM Name
newMetaTyVarName (String -> FastString
fsLit String
wc_nm)
       ; let kv :: TyVar
kv      = Name -> Type -> TcTyVarDetails -> TyVar
mkTcTyVar Name
kv_name Type
liftedTypeKind TcTyVarDetails
kv_details
             wc_kind :: Type
wc_kind = TyVar -> Type
mkTyVarTy TyVar
kv
             wc_tv :: TyVar
wc_tv   = Name -> Type -> TcTyVarDetails -> TyVar
mkTcTyVar Name
wc_name Type
wc_kind TcTyVarDetails
wc_details

       ; String -> SDoc -> TcM ()
traceTc String
"tcAnonWildCardOcc" (TcLevel -> SDoc
forall a. Outputable a => a -> SDoc
ppr TcLevel
hole_lvl SDoc -> SDoc -> SDoc
<+> Bool -> SDoc
forall a. Outputable a => a -> SDoc
ppr Bool
emit_holes)
       ; Bool -> TcM () -> TcM ()
forall (f :: * -> *). Applicative f => Bool -> f () -> f ()
when Bool
emit_holes (TcM () -> TcM ()) -> TcM () -> TcM ()
forall a b. (a -> b) -> a -> b
$
         IsExtraConstraint -> TyVar -> TcM ()
emitAnonTypeHole IsExtraConstraint
is_extra TyVar
wc_tv
         -- Why the 'when' guard?
         -- See Note [Wildcards in visible kind application]

       -- You might think that this would always just unify
       -- wc_kind with exp_kind, so we could avoid even creating kv
       -- But the level numbers might not allow that unification,
       -- so we have to do it properly (T14140a)
       ; HasDebugCallStack =>
HsType GhcRn -> Type -> Type -> Type -> TcM Type
HsType GhcRn -> Type -> Type -> Type -> TcM Type
checkExpectedKind HsType GhcRn
ty (TyVar -> Type
mkTyVarTy TyVar
wc_tv) Type
wc_kind Type
exp_kind }
  where
     -- See Note [Wildcard names]
     wc_nm :: String
wc_nm = case HoleMode
hole_mode of
               HoleMode
HM_Sig      -> String
"w"
               HoleMode
HM_FamPat   -> String
"_"
               HoleMode
HM_VTA      -> String
"w"
               HoleMode
HM_TyAppPat -> String
"_"

     emit_holes :: Bool
emit_holes = case HoleMode
hole_mode of
                     HoleMode
HM_Sig     -> Bool
True
                     HoleMode
HM_FamPat  -> Bool
False
                     HoleMode
HM_VTA     -> Bool
False
                     HoleMode
HM_TyAppPat -> Bool
False

tcAnonWildCardOcc IsExtraConstraint
_ TcTyMode
mode HsType GhcRn
ty Type
_
-- mode_holes is Nothing.  Should not happen, because renamer
-- should already have rejected holes in unexpected places
  = String -> SDoc -> TcM Type
forall a. HasCallStack => String -> SDoc -> a
pprPanic String
"tcWildCardOcc" (TcTyMode -> SDoc
forall a. Outputable a => a -> SDoc
ppr TcTyMode
mode SDoc -> SDoc -> SDoc
$$ HsType GhcRn -> SDoc
forall a. Outputable a => a -> SDoc
ppr HsType GhcRn
ty)

{- Note [Wildcard names]
~~~~~~~~~~~~~~~~~~~~~~~~
So we hackily use the mode_holes flag to control the name used
for wildcards:

* For proper holes (whether in a visible type application (VTA) or no),
  we rename the '_' to 'w'. This is so that we see variables like 'w0'
  or 'w1' in error messages, a vast improvement upon '_0' and '_1'. For
  example, we prefer
       Found type wildcard ‘_’ standing for ‘w0’
  over
       Found type wildcard ‘_’ standing for ‘_1’

  Even in the VTA case, where we do not emit an error to be printed, we
  want to do the renaming, as the variables may appear in other,
  non-wildcard error messages.

* However, holes in the left-hand sides of type families ("type
  patterns") stand for type variables which we do not care to name --
  much like the use of an underscore in an ordinary term-level
  pattern. When we spot these, we neither wish to generate an error
  message nor to rename the variable.  We don't rename the variable so
  that we can pretty-print a type family LHS as, e.g.,
    F _ Int _ = ...
  and not
     F w1 Int w2 = ...

  See also Note [Wildcards in family instances] in
  GHC.Rename.Module. The choice of HM_FamPat is made in
  tcFamTyPats. There is also some unsavory magic, relying on that
  underscore, in GHC.Core.Coercion.tidyCoAxBndrsForUser.

Note [Wildcards in visible kind application]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
There are cases where users might want to pass in a wildcard as a visible kind
argument, for instance:

data T :: forall k1 k2. k1 → k2 → Type where
  MkT :: T a b
x :: T @_ @Nat False n
x = MkT

So we should allow '@_' without emitting any hole constraints, and
regardless of whether PartialTypeSignatures is enabled or not. But how
would the typechecker know which '_' is being used in VKA and which is
not when it calls emitNamedTypeHole in
tcHsPartialSigType on all HsWildCardBndrs?  The solution is to neither
rename nor include unnamed wildcards in HsWildCardBndrs, but instead
give every anonymous wildcard a fresh wild tyvar in tcAnonWildCardOcc.

And whenever we see a '@', we set mode_holes to HM_VKA, so that
we do not call emitAnonTypeHole in tcAnonWildCardOcc.
See related Note [Wildcards in visible type application] here and
Note [The wildcard story for types] in GHC.Hs.Type
-}

{- *********************************************************************
*                                                                      *
             Kind inference for type declarations
*                                                                      *
********************************************************************* -}

-- See Note [kcCheckDeclHeader vs kcInferDeclHeader]
data InitialKindStrategy
  = InitialKindCheck SAKS_or_CUSK
  | InitialKindInfer

-- Does the declaration have a standalone kind signature (SAKS) or a complete
-- user-specified kind (CUSK)?
data SAKS_or_CUSK
  = SAKS Kind  -- Standalone kind signature, fully zonked! (zonkTcTypeToType)
  | CUSK       -- Complete user-specified kind (CUSK)

instance Outputable SAKS_or_CUSK where
  ppr :: SAKS_or_CUSK -> SDoc
ppr (SAKS Type
k) = String -> SDoc
text String
"SAKS" SDoc -> SDoc -> SDoc
<+> Type -> SDoc
forall a. Outputable a => a -> SDoc
ppr Type
k
  ppr SAKS_or_CUSK
CUSK = String -> SDoc
text String
"CUSK"

-- See Note [kcCheckDeclHeader vs kcInferDeclHeader]
kcDeclHeader
  :: InitialKindStrategy
  -> Name              -- ^ of the thing being checked
  -> TyConFlavour      -- ^ What sort of 'TyCon' is being checked
  -> LHsQTyVars GhcRn  -- ^ Binders in the header
  -> TcM ContextKind   -- ^ The result kind
  -> TcM TcTyCon       -- ^ A suitably-kinded TcTyCon
kcDeclHeader :: InitialKindStrategy
-> Name
-> TyConFlavour
-> LHsQTyVars GhcRn
-> TcM ContextKind
-> TcM TyCon
kcDeclHeader (InitialKindCheck SAKS_or_CUSK
msig) = SAKS_or_CUSK
-> Name
-> TyConFlavour
-> LHsQTyVars GhcRn
-> TcM ContextKind
-> TcM TyCon
kcCheckDeclHeader SAKS_or_CUSK
msig
kcDeclHeader InitialKindStrategy
InitialKindInfer = Name
-> TyConFlavour -> LHsQTyVars GhcRn -> TcM ContextKind -> TcM TyCon
kcInferDeclHeader

{- Note [kcCheckDeclHeader vs kcInferDeclHeader]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
kcCheckDeclHeader and kcInferDeclHeader are responsible for getting the initial kind
of a type constructor.

* kcCheckDeclHeader: the TyCon has a standalone kind signature or a CUSK. In that
  case, find the full, final, poly-kinded kind of the TyCon.  It's very like a
  term-level binding where we have a complete type signature for the function.

* kcInferDeclHeader: the TyCon has neither a standalone kind signature nor a
  CUSK. Find a monomorphic kind, with unification variables in it; they will be
  generalised later.  It's very like a term-level binding where we do not have a
  type signature (or, more accurately, where we have a partial type signature),
  so we infer the type and generalise.
-}

------------------------------
kcCheckDeclHeader
  :: SAKS_or_CUSK
  -> Name              -- ^ of the thing being checked
  -> TyConFlavour      -- ^ What sort of 'TyCon' is being checked
  -> LHsQTyVars GhcRn  -- ^ Binders in the header
  -> TcM ContextKind   -- ^ The result kind. AnyKind == no result signature
  -> TcM TcTyCon       -- ^ A suitably-kinded generalized TcTyCon
kcCheckDeclHeader :: SAKS_or_CUSK
-> Name
-> TyConFlavour
-> LHsQTyVars GhcRn
-> TcM ContextKind
-> TcM TyCon
kcCheckDeclHeader (SAKS Type
sig) = Type
-> Name
-> TyConFlavour
-> LHsQTyVars GhcRn
-> TcM ContextKind
-> TcM TyCon
kcCheckDeclHeader_sig Type
sig
kcCheckDeclHeader SAKS_or_CUSK
CUSK       = Name
-> TyConFlavour -> LHsQTyVars GhcRn -> TcM ContextKind -> TcM TyCon
kcCheckDeclHeader_cusk

kcCheckDeclHeader_cusk
  :: Name              -- ^ of the thing being checked
  -> TyConFlavour      -- ^ What sort of 'TyCon' is being checked
  -> LHsQTyVars GhcRn  -- ^ Binders in the header
  -> TcM ContextKind   -- ^ The result kind
  -> TcM TcTyCon       -- ^ A suitably-kinded generalized TcTyCon
kcCheckDeclHeader_cusk :: Name
-> TyConFlavour -> LHsQTyVars GhcRn -> TcM ContextKind -> TcM TyCon
kcCheckDeclHeader_cusk Name
name TyConFlavour
flav
              (HsQTvs { hsq_ext :: forall pass. LHsQTyVars pass -> XHsQTvs pass
hsq_ext = XHsQTvs GhcRn
kv_ns
                      , hsq_explicit :: forall pass. LHsQTyVars pass -> [LHsTyVarBndr () pass]
hsq_explicit = [LHsTyVarBndr () GhcRn]
hs_tvs }) TcM ContextKind
kc_res_ki
  -- CUSK case
  -- See note [Required, Specified, and Inferred for types] in GHC.Tc.TyCl
  = Name -> TyConFlavour -> TcM TyCon -> TcM TyCon
forall a. Name -> TyConFlavour -> TcM a -> TcM a
addTyConFlavCtxt Name
name TyConFlavour
flav (TcM TyCon -> TcM TyCon) -> TcM TyCon -> TcM TyCon
forall a b. (a -> b) -> a -> b
$
    do { (TcLevel
tclvl, WantedConstraints
wanted, ([TyVar]
scoped_kvs, ([TyVar]
tc_tvs, Type
res_kind)))
           <- String
-> TcM ([TyVar], ([TyVar], Type))
-> TcM (TcLevel, WantedConstraints, ([TyVar], ([TyVar], Type)))
forall a. String -> TcM a -> TcM (TcLevel, WantedConstraints, a)
pushLevelAndSolveEqualitiesX String
"kcCheckDeclHeader_cusk" (TcM ([TyVar], ([TyVar], Type))
 -> TcM (TcLevel, WantedConstraints, ([TyVar], ([TyVar], Type))))
-> TcM ([TyVar], ([TyVar], Type))
-> TcM (TcLevel, WantedConstraints, ([TyVar], ([TyVar], Type)))
forall a b. (a -> b) -> a -> b
$
              HsQTvsRn -> TcM ([TyVar], Type) -> TcM ([TyVar], ([TyVar], Type))
forall a. HsQTvsRn -> TcM a -> TcM ([TyVar], a)
bindImplicitTKBndrs_Q_Skol HsQTvsRn
XHsQTvs GhcRn
kv_ns                      (TcM ([TyVar], Type) -> TcM ([TyVar], ([TyVar], Type)))
-> TcM ([TyVar], Type) -> TcM ([TyVar], ([TyVar], Type))
forall a b. (a -> b) -> a -> b
$
              ContextKind
-> [LHsTyVarBndr () GhcRn] -> TcM Type -> TcM ([TyVar], Type)
forall a.
ContextKind -> [LHsTyVarBndr () GhcRn] -> TcM a -> TcM ([TyVar], a)
bindExplicitTKBndrs_Q_Skol ContextKind
ctxt_kind [LHsTyVarBndr () GhcRn]
hs_tvs           (TcM Type -> TcM ([TyVar], Type))
-> TcM Type -> TcM ([TyVar], Type)
forall a b. (a -> b) -> a -> b
$
              ContextKind -> TcM Type
newExpectedKind (ContextKind -> TcM Type) -> TcM ContextKind -> TcM Type
forall (m :: * -> *) a b. Monad m => (a -> m b) -> m a -> m b
=<< TcM ContextKind
kc_res_ki

           -- Now, because we're in a CUSK,
           -- we quantify over the mentioned kind vars
       ; let spec_req_tkvs :: [TyVar]
spec_req_tkvs = [TyVar]
scoped_kvs [TyVar] -> [TyVar] -> [TyVar]
forall a. [a] -> [a] -> [a]
++ [TyVar]
tc_tvs
             all_kinds :: [Type]
all_kinds     = Type
res_kind Type -> [Type] -> [Type]
forall a. a -> [a] -> [a]
: (TyVar -> Type) -> [TyVar] -> [Type]
forall a b. (a -> b) -> [a] -> [b]
map TyVar -> Type
tyVarKind [TyVar]
spec_req_tkvs

       ; CandidatesQTvs
candidates' <- [Type] -> TcM CandidatesQTvs
candidateQTyVarsOfKinds [Type]
all_kinds
             -- 'candidates' are all the variables that we are going to
             -- skolemise and then quantify over.  We do not include spec_req_tvs
             -- because they are /already/ skolems

       ; let non_tc_candidates :: [TyVar]
non_tc_candidates = (TyVar -> Bool) -> [TyVar] -> [TyVar]
forall a. (a -> Bool) -> [a] -> [a]
filter (Bool -> Bool
not (Bool -> Bool) -> (TyVar -> Bool) -> TyVar -> Bool
forall b c a. (b -> c) -> (a -> b) -> a -> c
. TyVar -> Bool
isTcTyVar) (VarSet -> [TyVar]
forall elt. UniqSet elt -> [elt]
nonDetEltsUniqSet ([Type] -> VarSet
tyCoVarsOfTypes [Type]
all_kinds))
             candidates :: CandidatesQTvs
candidates = CandidatesQTvs
candidates' { dv_kvs :: DTyVarSet
dv_kvs = CandidatesQTvs -> DTyVarSet
dv_kvs CandidatesQTvs
candidates' DTyVarSet -> [TyVar] -> DTyVarSet
`extendDVarSetList` [TyVar]
non_tc_candidates }
             inf_candidates :: CandidatesQTvs
inf_candidates = CandidatesQTvs
candidates CandidatesQTvs -> [TyVar] -> CandidatesQTvs
`delCandidates` [TyVar]
spec_req_tkvs

       ; [TyVar]
inferred <- CandidatesQTvs -> TcM [TyVar]
quantifyTyVars CandidatesQTvs
inf_candidates
                     -- NB: 'inferred' comes back sorted in dependency order

       ; [TyVar]
scoped_kvs <- (TyVar -> IOEnv (Env TcGblEnv TcLclEnv) TyVar)
-> [TyVar] -> TcM [TyVar]
forall (t :: * -> *) (m :: * -> *) a b.
(Traversable t, Monad m) =>
(a -> m b) -> t a -> m (t b)
mapM TyVar -> IOEnv (Env TcGblEnv TcLclEnv) TyVar
zonkTyCoVarKind [TyVar]
scoped_kvs
       ; [TyVar]
tc_tvs     <- (TyVar -> IOEnv (Env TcGblEnv TcLclEnv) TyVar)
-> [TyVar] -> TcM [TyVar]
forall (t :: * -> *) (m :: * -> *) a b.
(Traversable t, Monad m) =>
(a -> m b) -> t a -> m (t b)
mapM TyVar -> IOEnv (Env TcGblEnv TcLclEnv) TyVar
zonkTyCoVarKind [TyVar]
tc_tvs
       ; Type
res_kind   <- Type -> TcM Type
zonkTcType           Type
res_kind

       ; let mentioned_kv_set :: VarSet
mentioned_kv_set = CandidatesQTvs -> VarSet
candidateKindVars CandidatesQTvs
candidates
             specified :: [TyVar]
specified        = [TyVar] -> [TyVar]
scopedSort [TyVar]
scoped_kvs
                                -- NB: maintain the L-R order of scoped_kvs

             final_tc_binders :: [TyConBinder]
final_tc_binders =  ArgFlag -> [TyVar] -> [TyConBinder]
mkNamedTyConBinders ArgFlag
Inferred  [TyVar]
inferred
                              [TyConBinder] -> [TyConBinder] -> [TyConBinder]
forall a. [a] -> [a] -> [a]
++ ArgFlag -> [TyVar] -> [TyConBinder]
mkNamedTyConBinders ArgFlag
Specified [TyVar]
specified
                              [TyConBinder] -> [TyConBinder] -> [TyConBinder]
forall a. [a] -> [a] -> [a]
++ (TyVar -> TyConBinder) -> [TyVar] -> [TyConBinder]
forall a b. (a -> b) -> [a] -> [b]
map (VarSet -> TyVar -> TyConBinder
mkRequiredTyConBinder VarSet
mentioned_kv_set) [TyVar]
tc_tvs

             all_tv_prs :: [(Name, TyVar)]
all_tv_prs =  [TyVar] -> [(Name, TyVar)]
mkTyVarNamePairs ([TyVar]
scoped_kvs [TyVar] -> [TyVar] -> [TyVar]
forall a. [a] -> [a] -> [a]
++ [TyVar]
tc_tvs)
             tycon :: TyCon
tycon = Name
-> [TyConBinder]
-> Type
-> [(Name, TyVar)]
-> Bool
-> TyConFlavour
-> TyCon
mkTcTyCon Name
name [TyConBinder]
final_tc_binders Type
res_kind [(Name, TyVar)]
all_tv_prs
                               Bool
True -- it is generalised
                               TyConFlavour
flav

       ; SkolemInfo -> [TyVar] -> TcLevel -> WantedConstraints -> TcM ()
reportUnsolvedEqualities SkolemInfo
skol_info ([TyConBinder] -> [TyVar]
forall tv argf. [VarBndr tv argf] -> [tv]
binderVars [TyConBinder]
final_tc_binders)
                                  TcLevel
tclvl WantedConstraints
wanted

         -- If the ordering from
         -- Note [Required, Specified, and Inferred for types] in GHC.Tc.TyCl
         -- doesn't work, we catch it here, before an error cascade
       ; TyCon -> TcM ()
checkTyConTelescope TyCon
tycon

       ; String -> SDoc -> TcM ()
traceTc String
"kcCheckDeclHeader_cusk " (SDoc -> TcM ()) -> SDoc -> TcM ()
forall a b. (a -> b) -> a -> b
$
         [SDoc] -> SDoc
vcat [ String -> SDoc
text String
"name" SDoc -> SDoc -> SDoc
<+> Name -> SDoc
forall a. Outputable a => a -> SDoc
ppr Name
name
              , String -> SDoc
text String
"kv_ns" SDoc -> SDoc -> SDoc
<+> HsQTvsRn -> SDoc
forall a. Outputable a => a -> SDoc
ppr HsQTvsRn
XHsQTvs GhcRn
kv_ns
              , String -> SDoc
text String
"hs_tvs" SDoc -> SDoc -> SDoc
<+> [GenLocated SrcSpanAnnA (HsTyVarBndr () GhcRn)] -> SDoc
forall a. Outputable a => a -> SDoc
ppr [GenLocated SrcSpanAnnA (HsTyVarBndr () GhcRn)]
[LHsTyVarBndr () GhcRn]
hs_tvs
              , String -> SDoc
text String
"scoped_kvs" SDoc -> SDoc -> SDoc
<+> [TyVar] -> SDoc
forall a. Outputable a => a -> SDoc
ppr [TyVar]
scoped_kvs
              , String -> SDoc
text String
"tc_tvs" SDoc -> SDoc -> SDoc
<+> [TyVar] -> SDoc
forall a. Outputable a => a -> SDoc
ppr [TyVar]
tc_tvs
              , String -> SDoc
text String
"res_kind" SDoc -> SDoc -> SDoc
<+> Type -> SDoc
forall a. Outputable a => a -> SDoc
ppr Type
res_kind
              , String -> SDoc
text String
"candidates" SDoc -> SDoc -> SDoc
<+> CandidatesQTvs -> SDoc
forall a. Outputable a => a -> SDoc
ppr CandidatesQTvs
candidates
              , String -> SDoc
text String
"inferred" SDoc -> SDoc -> SDoc
<+> [TyVar] -> SDoc
forall a. Outputable a => a -> SDoc
ppr [TyVar]
inferred
              , String -> SDoc
text String
"specified" SDoc -> SDoc -> SDoc
<+> [TyVar] -> SDoc
forall a. Outputable a => a -> SDoc
ppr [TyVar]
specified
              , String -> SDoc
text String
"final_tc_binders" SDoc -> SDoc -> SDoc
<+> [TyConBinder] -> SDoc
forall a. Outputable a => a -> SDoc
ppr [TyConBinder]
final_tc_binders
              , String -> SDoc
text String
"mkTyConKind final_tc_bndrs res_kind"
                SDoc -> SDoc -> SDoc
<+> Type -> SDoc
forall a. Outputable a => a -> SDoc
ppr ([TyConBinder] -> Type -> Type
mkTyConKind [TyConBinder]
final_tc_binders Type
res_kind)
              , String -> SDoc
text String
"all_tv_prs" SDoc -> SDoc -> SDoc
<+> [(Name, TyVar)] -> SDoc
forall a. Outputable a => a -> SDoc
ppr [(Name, TyVar)]
all_tv_prs ]

       ; TyCon -> TcM TyCon
forall (m :: * -> *) a. Monad m => a -> m a
return TyCon
tycon }
  where
    skol_info :: SkolemInfo
skol_info = TyConFlavour -> Name -> SkolemInfo
TyConSkol TyConFlavour
flav Name
name
    ctxt_kind :: ContextKind
ctxt_kind | TyConFlavour -> Bool
tcFlavourIsOpen TyConFlavour
flav = Type -> ContextKind
TheKind Type
liftedTypeKind
              | Bool
otherwise            = ContextKind
AnyKind

-- | Kind-check a 'LHsQTyVars'. Used in 'inferInitialKind' (for tycon kinds and
-- other kinds).
--
-- This function does not do telescope checking.
kcInferDeclHeader
  :: Name              -- ^ of the thing being checked
  -> TyConFlavour      -- ^ What sort of 'TyCon' is being checked
  -> LHsQTyVars GhcRn
  -> TcM ContextKind   -- ^ The result kind
  -> TcM TcTyCon       -- ^ A suitably-kinded non-generalized TcTyCon
kcInferDeclHeader :: Name
-> TyConFlavour -> LHsQTyVars GhcRn -> TcM ContextKind -> TcM TyCon
kcInferDeclHeader Name
name TyConFlavour
flav
              (HsQTvs { hsq_ext :: forall pass. LHsQTyVars pass -> XHsQTvs pass
hsq_ext = XHsQTvs GhcRn
kv_ns
                      , hsq_explicit :: forall pass. LHsQTyVars pass -> [LHsTyVarBndr () pass]
hsq_explicit = [LHsTyVarBndr () GhcRn]
hs_tvs }) TcM ContextKind
kc_res_ki
  -- No standalane kind signature and no CUSK.
  -- See note [Required, Specified, and Inferred for types] in GHC.Tc.TyCl
  = Name -> TyConFlavour -> TcM TyCon -> TcM TyCon
forall a. Name -> TyConFlavour -> TcM a -> TcM a
addTyConFlavCtxt Name
name TyConFlavour
flav (TcM TyCon -> TcM TyCon) -> TcM TyCon -> TcM TyCon
forall a b. (a -> b) -> a -> b
$
    do { ([TyVar]
scoped_kvs, ([TyVar]
tc_tvs, Type
res_kind))
           -- Why bindImplicitTKBndrs_Q_Tv which uses newTyVarTyVar?
           -- See Note [Inferring kinds for type declarations] in GHC.Tc.TyCl
           <- HsQTvsRn -> TcM ([TyVar], Type) -> TcM ([TyVar], ([TyVar], Type))
forall a. HsQTvsRn -> TcM a -> TcM ([TyVar], a)
bindImplicitTKBndrs_Q_Tv HsQTvsRn
XHsQTvs GhcRn
kv_ns            (TcM ([TyVar], Type) -> TcM ([TyVar], ([TyVar], Type)))
-> TcM ([TyVar], Type) -> TcM ([TyVar], ([TyVar], Type))
forall a b. (a -> b) -> a -> b
$
              ContextKind
-> [LHsTyVarBndr () GhcRn] -> TcM Type -> TcM ([TyVar], Type)
forall a.
ContextKind -> [LHsTyVarBndr () GhcRn] -> TcM a -> TcM ([TyVar], a)
bindExplicitTKBndrs_Q_Tv ContextKind
ctxt_kind [LHsTyVarBndr () GhcRn]
hs_tvs (TcM Type -> TcM ([TyVar], Type))
-> TcM Type -> TcM ([TyVar], Type)
forall a b. (a -> b) -> a -> b
$
              ContextKind -> TcM Type
newExpectedKind (ContextKind -> TcM Type) -> TcM ContextKind -> TcM Type
forall (m :: * -> *) a b. Monad m => (a -> m b) -> m a -> m b
=<< TcM ContextKind
kc_res_ki
              -- Why "_Tv" not "_Skol"? See third wrinkle in
              -- Note [Inferring kinds for type declarations] in GHC.Tc.TyCl,

       ; let   -- NB: Don't add scoped_kvs to tyConTyVars, because they
               -- might unify with kind vars in other types in a mutually
               -- recursive group.
               -- See Note [Inferring kinds for type declarations] in GHC.Tc.TyCl

             tc_binders :: [TyConBinder]
tc_binders = AnonArgFlag -> [TyVar] -> [TyConBinder]
mkAnonTyConBinders AnonArgFlag
VisArg [TyVar]
tc_tvs
               -- Also, note that tc_binders has the tyvars from only the
               -- user-written tyvarbinders. See S1 in Note [How TcTyCons work]
               -- in GHC.Tc.TyCl
               --
               -- mkAnonTyConBinder: see Note [No polymorphic recursion]

             all_tv_prs :: [(Name, TyVar)]
all_tv_prs = [TyVar] -> [(Name, TyVar)]
mkTyVarNamePairs ([TyVar]
scoped_kvs [TyVar] -> [TyVar] -> [TyVar]
forall a. [a] -> [a] -> [a]
++ [TyVar]
tc_tvs)
               -- NB: bindExplicitTKBndrs_Q_Tv does not clone;
               --     ditto Implicit
               -- See Note [Cloning for type variable binders]

             tycon :: TyCon
tycon = Name
-> [TyConBinder]
-> Type
-> [(Name, TyVar)]
-> Bool
-> TyConFlavour
-> TyCon
mkTcTyCon Name
name [TyConBinder]
tc_binders Type
res_kind [(Name, TyVar)]
all_tv_prs
                               Bool
False -- not yet generalised
                               TyConFlavour
flav

       ; String -> SDoc -> TcM ()
traceTc String
"kcInferDeclHeader: not-cusk" (SDoc -> TcM ()) -> SDoc -> TcM ()
forall a b. (a -> b) -> a -> b
$
         [SDoc] -> SDoc
vcat [ Name -> SDoc
forall a. Outputable a => a -> SDoc
ppr Name
name, HsQTvsRn -> SDoc
forall a. Outputable a => a -> SDoc
ppr HsQTvsRn
XHsQTvs GhcRn
kv_ns, [GenLocated SrcSpanAnnA (HsTyVarBndr () GhcRn)] -> SDoc
forall a. Outputable a => a -> SDoc
ppr [GenLocated SrcSpanAnnA (HsTyVarBndr () GhcRn)]
[LHsTyVarBndr () GhcRn]
hs_tvs
              , [TyVar] -> SDoc
forall a. Outputable a => a -> SDoc
ppr [TyVar]
scoped_kvs
              , [TyVar] -> SDoc
forall a. Outputable a => a -> SDoc
ppr [TyVar]
tc_tvs, Type -> SDoc
forall a. Outputable a => a -> SDoc
ppr ([TyConBinder] -> Type -> Type
mkTyConKind [TyConBinder]
tc_binders Type
res_kind) ]
       ; TyCon -> TcM TyCon
forall (m :: * -> *) a. Monad m => a -> m a
return TyCon
tycon }
  where
    ctxt_kind :: ContextKind
ctxt_kind | TyConFlavour -> Bool
tcFlavourIsOpen TyConFlavour
flav = Type -> ContextKind
TheKind Type
liftedTypeKind
              | Bool
otherwise            = ContextKind
AnyKind

-- | Kind-check a declaration header against a standalone kind signature.
-- See Note [Arity inference in kcCheckDeclHeader_sig]
kcCheckDeclHeader_sig
  :: Kind              -- ^ Standalone kind signature, fully zonked! (zonkTcTypeToType)
  -> Name              -- ^ of the thing being checked
  -> TyConFlavour      -- ^ What sort of 'TyCon' is being checked
  -> LHsQTyVars GhcRn  -- ^ Binders in the header
  -> TcM ContextKind   -- ^ The result kind. AnyKind == no result signature
  -> TcM TcTyCon       -- ^ A suitably-kinded TcTyCon
kcCheckDeclHeader_sig :: Type
-> Name
-> TyConFlavour
-> LHsQTyVars GhcRn
-> TcM ContextKind
-> TcM TyCon
kcCheckDeclHeader_sig Type
kisig Name
name TyConFlavour
flav
          (HsQTvs { hsq_ext :: forall pass. LHsQTyVars pass -> XHsQTvs pass
hsq_ext      = XHsQTvs GhcRn
implicit_nms
                  , hsq_explicit :: forall pass. LHsQTyVars pass -> [LHsTyVarBndr () pass]
hsq_explicit = [LHsTyVarBndr () GhcRn]
explicit_nms }) TcM ContextKind
kc_res_ki
  = Name -> TyConFlavour -> TcM TyCon -> TcM TyCon
forall a. Name -> TyConFlavour -> TcM a -> TcM a
addTyConFlavCtxt Name
name TyConFlavour
flav (TcM TyCon -> TcM TyCon) -> TcM TyCon -> TcM TyCon
forall a b. (a -> b) -> a -> b
$
    do {  -- Step 1: zip user-written binders with quantifiers from the kind signature.
          -- For example:
          --
          --   type F :: forall k -> k -> forall j. j -> Type
          --   data F i a b = ...
          --
          -- Results in the following 'zipped_binders':
          --
          --                   TyBinder      LHsTyVarBndr
          --    ---------------------------------------
          --    ZippedBinder   forall k ->   i
          --    ZippedBinder   k ->          a
          --    ZippedBinder   forall j.
          --    ZippedBinder   j ->          b
          --
          let ([ZippedBinder]
zipped_binders, [LHsTyVarBndr () GhcRn]
excess_bndrs, Type
kisig') = Type
-> [LHsTyVarBndr () GhcRn]
-> ([ZippedBinder], [LHsTyVarBndr () GhcRn], Type)
zipBinders Type
kisig [LHsTyVarBndr () GhcRn]
explicit_nms

          -- Report binders that don't have a corresponding quantifier.
          -- For example:
          --
          --   type T :: Type -> Type
          --   data T b1 b2 b3 = ...
          --
          -- Here, b1 is zipped with Type->, while b2 and b3 are excess binders.
          --
        ; Bool -> TcM () -> TcM ()
forall (f :: * -> *). Applicative f => Bool -> f () -> f ()
unless ([GenLocated SrcSpanAnnA (HsTyVarBndr () GhcRn)] -> Bool
forall (t :: * -> *) a. Foldable t => t a -> Bool
null [GenLocated SrcSpanAnnA (HsTyVarBndr () GhcRn)]
[LHsTyVarBndr () GhcRn]
excess_bndrs) (TcM () -> TcM ()) -> TcM () -> TcM ()
forall a b. (a -> b) -> a -> b
$ SDoc -> TcM ()
forall a. SDoc -> TcM a
failWithTc (Type -> [LHsTyVarBndr () GhcRn] -> SDoc
tooManyBindersErr Type
kisig' [LHsTyVarBndr () GhcRn]
excess_bndrs)

          -- Convert each ZippedBinder to TyConBinder        for  tyConBinders
          --                       and to [(Name, TcTyVar)]  for  tcTyConScopedTyVars
        ; ([TyConBinder]
vis_tcbs, [[(Name, TyVar)]] -> [(Name, TyVar)]
forall (t :: * -> *) a. Foldable t => t [a] -> [a]
concat -> [(Name, TyVar)]
explicit_tv_prs) <- (ZippedBinder
 -> IOEnv (Env TcGblEnv TcLclEnv) (TyConBinder, [(Name, TyVar)]))
-> [ZippedBinder]
-> IOEnv (Env TcGblEnv TcLclEnv) ([TyConBinder], [[(Name, TyVar)]])
forall (m :: * -> *) a b c.
Applicative m =>
(a -> m (b, c)) -> [a] -> m ([b], [c])
mapAndUnzipM ZippedBinder
-> IOEnv (Env TcGblEnv TcLclEnv) (TyConBinder, [(Name, TyVar)])
zipped_to_tcb [ZippedBinder]
zipped_binders

        ; (TcLevel
tclvl, WantedConstraints
wanted, ([TyVar]
implicit_tvs, ([TyBinder]
invis_binders, Type
r_ki)))
             <- String
-> TcM ([TyVar], ([TyBinder], Type))
-> TcM (TcLevel, WantedConstraints, ([TyVar], ([TyBinder], Type)))
forall a. String -> TcM a -> TcM (TcLevel, WantedConstraints, a)
pushLevelAndSolveEqualitiesX String
"kcCheckDeclHeader_sig" (TcM ([TyVar], ([TyBinder], Type))
 -> TcM (TcLevel, WantedConstraints, ([TyVar], ([TyBinder], Type))))
-> TcM ([TyVar], ([TyBinder], Type))
-> TcM (TcLevel, WantedConstraints, ([TyVar], ([TyBinder], Type)))
forall a b. (a -> b) -> a -> b
$  -- #16687
                HsQTvsRn
-> TcM ([TyBinder], Type) -> TcM ([TyVar], ([TyBinder], Type))
forall a. HsQTvsRn -> TcM a -> TcM ([TyVar], a)
bindImplicitTKBndrs_Tv HsQTvsRn
XHsQTvs GhcRn
implicit_nms                  (TcM ([TyBinder], Type) -> TcM ([TyVar], ([TyBinder], Type)))
-> TcM ([TyBinder], Type) -> TcM ([TyVar], ([TyBinder], Type))
forall a b. (a -> b) -> a -> b
$
                [(Name, TyVar)] -> TcM ([TyBinder], Type) -> TcM ([TyBinder], Type)
forall r. [(Name, TyVar)] -> TcM r -> TcM r
tcExtendNameTyVarEnv [(Name, TyVar)]
explicit_tv_prs                 (TcM ([TyBinder], Type) -> TcM ([TyBinder], Type))
-> TcM ([TyBinder], Type) -> TcM ([TyBinder], Type)
forall a b. (a -> b) -> a -> b
$
                do { -- Check that inline kind annotations on binders are valid.
                     -- For example:
                     --
                     --   type T :: Maybe k -> Type
                     --   data T (a :: Maybe j) = ...
                     --
                     -- Here we unify   Maybe k ~ Maybe j
                     (ZippedBinder -> TcM ()) -> [ZippedBinder] -> TcM ()
forall (t :: * -> *) (m :: * -> *) a b.
(Foldable t, Monad m) =>
(a -> m b) -> t a -> m ()
mapM_ ZippedBinder -> TcM ()
check_zipped_binder [ZippedBinder]
zipped_binders

                     -- Kind-check the result kind annotation, if present:
                     --
                     --    data T a b :: res_ki where
                     --               ^^^^^^^^^
                     -- We do it here because at this point the environment has been
                     -- extended with both 'implicit_tcv_prs' and 'explicit_tv_prs'.
                   ; ContextKind
ctx_k    <- TcM ContextKind
kc_res_ki
                   ; Maybe Type
m_res_ki <- case ContextKind
ctx_k of
                                  ContextKind
AnyKind -> Maybe Type -> IOEnv (Env TcGblEnv TcLclEnv) (Maybe Type)
forall (m :: * -> *) a. Monad m => a -> m a
return Maybe Type
forall a. Maybe a
Nothing
                                  ContextKind
_ -> Type -> Maybe Type
forall a. a -> Maybe a
Just (Type -> Maybe Type)
-> TcM Type -> IOEnv (Env TcGblEnv TcLclEnv) (Maybe Type)
forall (f :: * -> *) a b. Functor f => (a -> b) -> f a -> f b
<$> ContextKind -> TcM Type
newExpectedKind ContextKind
ctx_k

                     -- Step 2: split off invisible binders.
                     -- For example:
                     --
                     --   type F :: forall k1 k2. (k1, k2) -> Type
                     --   type family F
                     --
                     -- Does 'forall k1 k2' become a part of 'tyConBinders' or 'tyConResKind'?
                     -- See Note [Arity inference in kcCheckDeclHeader_sig]
                   ; let ([TyBinder]
invis_binders, Type
r_ki) = Type -> Maybe Type -> ([TyBinder], Type)
split_invis Type
kisig' Maybe Type
m_res_ki

                     -- Check that the inline result kind annotation is valid.
                     -- For example:
                     --
                     --   type T :: Type -> Maybe k
                     --   type family T a :: Maybe j where
                     --
                     -- Here we unify   Maybe k ~ Maybe j
                   ; Maybe Type -> (Type -> TcM ()) -> TcM ()
forall (m :: * -> *) a. Monad m => Maybe a -> (a -> m ()) -> m ()
whenIsJust Maybe Type
m_res_ki ((Type -> TcM ()) -> TcM ()) -> (Type -> TcM ()) -> TcM ()
forall a b. (a -> b) -> a -> b
$ \Type
res_ki ->
                      TcM Coercion -> TcM ()
forall a. TcM a -> TcM ()
discardResult (TcM Coercion -> TcM ()) -> TcM Coercion -> TcM ()
forall a b. (a -> b) -> a -> b
$ -- See Note [discardResult in kcCheckDeclHeader_sig]
                      Maybe SDoc -> Type -> Type -> TcM Coercion
unifyKind Maybe SDoc
forall a. Maybe a
Nothing Type
r_ki Type
res_ki

                   ; ([TyBinder], Type) -> TcM ([TyBinder], Type)
forall (m :: * -> *) a. Monad m => a -> m a
return ([TyBinder]
invis_binders, Type
r_ki) }

        -- Convert each invisible TyCoBinder to TyConBinder for tyConBinders.
        ; [TyConBinder]
invis_tcbs <- (TyBinder -> IOEnv (Env TcGblEnv TcLclEnv) TyConBinder)
-> [TyBinder] -> IOEnv (Env TcGblEnv TcLclEnv) [TyConBinder]
forall (t :: * -> *) (m :: * -> *) a b.
(Traversable t, Monad m) =>
(a -> m b) -> t a -> m (t b)
mapM TyBinder -> IOEnv (Env TcGblEnv TcLclEnv) TyConBinder
invis_to_tcb [TyBinder]
invis_binders

        -- Zonk the implicitly quantified variables.
        ; [TyVar]
implicit_tvs <- (TyVar -> IOEnv (Env TcGblEnv TcLclEnv) TyVar)
-> [TyVar] -> TcM [TyVar]
forall (t :: * -> *) (m :: * -> *) a b.
(Traversable t, Monad m) =>
(a -> m b) -> t a -> m (t b)
mapM HasDebugCallStack => TyVar -> IOEnv (Env TcGblEnv TcLclEnv) TyVar
TyVar -> IOEnv (Env TcGblEnv TcLclEnv) TyVar
zonkTcTyVarToTyVar [TyVar]
implicit_tvs

        -- Build the final, generalized TcTyCon
        ; let tcbs :: [TyConBinder]
tcbs            = [TyConBinder]
vis_tcbs [TyConBinder] -> [TyConBinder] -> [TyConBinder]
forall a. [a] -> [a] -> [a]
++ [TyConBinder]
invis_tcbs
              implicit_tv_prs :: [(Name, TyVar)]
implicit_tv_prs = HsQTvsRn
XHsQTvs GhcRn
implicit_nms HsQTvsRn -> [TyVar] -> [(Name, TyVar)]
forall a b. [a] -> [b] -> [(a, b)]
`zip` [TyVar]
implicit_tvs
              all_tv_prs :: [(Name, TyVar)]
all_tv_prs      = [(Name, TyVar)]
implicit_tv_prs [(Name, TyVar)] -> [(Name, TyVar)] -> [(Name, TyVar)]
forall a. [a] -> [a] -> [a]
++ [(Name, TyVar)]
explicit_tv_prs
              tc :: TyCon
tc              = Name
-> [TyConBinder]
-> Type
-> [(Name, TyVar)]
-> Bool
-> TyConFlavour
-> TyCon
mkTcTyCon Name
name [TyConBinder]
tcbs Type
r_ki [(Name, TyVar)]
all_tv_prs Bool
True TyConFlavour
flav
              skol_info :: SkolemInfo
skol_info       = TyConFlavour -> Name -> SkolemInfo
TyConSkol TyConFlavour
flav Name
name

        -- Check that there are no unsolved equalities
        ; SkolemInfo -> [TyVar] -> TcLevel -> WantedConstraints -> TcM ()
reportUnsolvedEqualities SkolemInfo
skol_info ([TyConBinder] -> [TyVar]
forall tv argf. [VarBndr tv argf] -> [tv]
binderVars [TyConBinder]
tcbs) TcLevel
tclvl WantedConstraints
wanted

        ; String -> SDoc -> TcM ()
traceTc String
"kcCheckDeclHeader_sig done:" (SDoc -> TcM ()) -> SDoc -> TcM ()
forall a b. (a -> b) -> a -> b
$ [SDoc] -> SDoc
vcat
          [ String -> SDoc
text String
"tyConName = " SDoc -> SDoc -> SDoc
<+> Name -> SDoc
forall a. Outputable a => a -> SDoc
ppr (TyCon -> Name
tyConName TyCon
tc)
          , String -> SDoc
text String
"kisig =" SDoc -> SDoc -> SDoc
<+> Type -> SDoc
debugPprType Type
kisig
          , String -> SDoc
text String
"tyConKind =" SDoc -> SDoc -> SDoc
<+> Type -> SDoc
debugPprType (TyCon -> Type
tyConKind TyCon
tc)
          , String -> SDoc
text String
"tyConBinders = " SDoc -> SDoc -> SDoc
<+> [TyConBinder] -> SDoc
forall a. Outputable a => a -> SDoc
ppr (TyCon -> [TyConBinder]
tyConBinders TyCon
tc)
          , String -> SDoc
text String
"tcTyConScopedTyVars" SDoc -> SDoc -> SDoc
<+> [(Name, TyVar)] -> SDoc
forall a. Outputable a => a -> SDoc
ppr (TyCon -> [(Name, TyVar)]
tcTyConScopedTyVars TyCon
tc)
          , String -> SDoc
text String
"tyConResKind" SDoc -> SDoc -> SDoc
<+> Type -> SDoc
debugPprType (TyCon -> Type
tyConResKind TyCon
tc)
          ]
        ; TyCon -> TcM TyCon
forall (m :: * -> *) a. Monad m => a -> m a
return TyCon
tc }
  where
    -- Consider this declaration:
    --
    --    type T :: forall a. forall b -> (a~b) => Proxy a -> Type
    --    data T x p = MkT
    --
    -- Here, we have every possible variant of ZippedBinder:
    --
    --                   TyBinder           LHsTyVarBndr
    --    ----------------------------------------------
    --    ZippedBinder   forall {k}.
    --    ZippedBinder   forall (a::k).
    --    ZippedBinder   forall (b::k) ->   x
    --    ZippedBinder   (a~b) =>
    --    ZippedBinder   Proxy a ->         p
    --
    -- Given a ZippedBinder zipped_to_tcb produces:
    --
    --  * TyConBinder      for  tyConBinders
    --  * (Name, TcTyVar)  for  tcTyConScopedTyVars, if there's a user-written LHsTyVarBndr
    --
    zipped_to_tcb :: ZippedBinder -> TcM (TyConBinder, [(Name, TcTyVar)])
    zipped_to_tcb :: ZippedBinder
-> IOEnv (Env TcGblEnv TcLclEnv) (TyConBinder, [(Name, TyVar)])
zipped_to_tcb ZippedBinder
zb = case ZippedBinder
zb of

      -- Inferred variable, no user-written binder.
      -- Example:   forall {k}.
      ZippedBinder (Named (Bndr TyVar
v ArgFlag
Specified)) Maybe (LHsTyVarBndr () GhcRn)
Nothing ->
        (TyConBinder, [(Name, TyVar)])
-> IOEnv (Env TcGblEnv TcLclEnv) (TyConBinder, [(Name, TyVar)])
forall (m :: * -> *) a. Monad m => a -> m a
return (ArgFlag -> TyVar -> TyConBinder
mkNamedTyConBinder ArgFlag
Specified TyVar
v, [])

      -- Specified variable, no user-written binder.
      -- Example:   forall (a::k).
      ZippedBinder (Named (Bndr TyVar
v ArgFlag
Inferred)) Maybe (LHsTyVarBndr () GhcRn)
Nothing ->
        (TyConBinder, [(Name, TyVar)])
-> IOEnv (Env TcGblEnv TcLclEnv) (TyConBinder, [(Name, TyVar)])
forall (m :: * -> *) a. Monad m => a -> m a
return (ArgFlag -> TyVar -> TyConBinder
mkNamedTyConBinder ArgFlag
Inferred TyVar
v, [])

      -- Constraint, no user-written binder.
      -- Example:   (a~b) =>
      ZippedBinder (Anon AnonArgFlag
InvisArg Scaled Type
bndr_ki) Maybe (LHsTyVarBndr () GhcRn)
Nothing -> do
        Name
name <- OccName -> TcM Name
forall gbl lcl. OccName -> TcRnIf gbl lcl Name
newSysName (FastString -> OccName
mkTyVarOccFS (String -> FastString
fsLit String
"ev"))
        let tv :: TyVar
tv = Name -> Type -> TyVar
mkTyVar Name
name (Scaled Type -> Type
forall a. Scaled a -> a
scaledThing Scaled Type
bndr_ki)
        (TyConBinder, [(Name, TyVar)])
-> IOEnv (Env TcGblEnv TcLclEnv) (TyConBinder, [(Name, TyVar)])
forall (m :: * -> *) a. Monad m => a -> m a
return (AnonArgFlag -> TyVar -> TyConBinder
mkAnonTyConBinder AnonArgFlag
InvisArg TyVar
tv, [])

      -- Non-dependent visible argument with a user-written binder.
      -- Example:   Proxy a ->
      ZippedBinder (Anon AnonArgFlag
VisArg Scaled Type
bndr_ki) (Just LHsTyVarBndr () GhcRn
b) ->
        (TyConBinder, [(Name, TyVar)])
-> IOEnv (Env TcGblEnv TcLclEnv) (TyConBinder, [(Name, TyVar)])
forall (m :: * -> *) a. Monad m => a -> m a
return ((TyConBinder, [(Name, TyVar)])
 -> IOEnv (Env TcGblEnv TcLclEnv) (TyConBinder, [(Name, TyVar)]))
-> (TyConBinder, [(Name, TyVar)])
-> IOEnv (Env TcGblEnv TcLclEnv) (TyConBinder, [(Name, TyVar)])
forall a b. (a -> b) -> a -> b
$
          let v_name :: Name
v_name = GenLocated SrcSpanAnnA (HsTyVarBndr () GhcRn) -> Name
forall a. NamedThing a => a -> Name
getName GenLocated SrcSpanAnnA (HsTyVarBndr () GhcRn)
LHsTyVarBndr () GhcRn
b
              tv :: TyVar
tv = Name -> Type -> TyVar
mkTyVar Name
v_name (Scaled Type -> Type
forall a. Scaled a -> a
scaledThing Scaled Type
bndr_ki)
              tcb :: TyConBinder
tcb = AnonArgFlag -> TyVar -> TyConBinder
mkAnonTyConBinder AnonArgFlag
VisArg TyVar
tv
          in (TyConBinder
tcb, [(Name
v_name, TyVar
tv)])

      -- Dependent visible argument with a user-written binder.
      -- Example:   forall (b::k) ->
      ZippedBinder (Named (Bndr TyVar
v ArgFlag
Required)) (Just LHsTyVarBndr () GhcRn
b) ->
        (TyConBinder, [(Name, TyVar)])
-> IOEnv (Env TcGblEnv TcLclEnv) (TyConBinder, [(Name, TyVar)])
forall (m :: * -> *) a. Monad m => a -> m a
return ((TyConBinder, [(Name, TyVar)])
 -> IOEnv (Env TcGblEnv TcLclEnv) (TyConBinder, [(Name, TyVar)]))
-> (TyConBinder, [(Name, TyVar)])
-> IOEnv (Env TcGblEnv TcLclEnv) (TyConBinder, [(Name, TyVar)])
forall a b. (a -> b) -> a -> b
$
          let v_name :: Name
v_name = GenLocated SrcSpanAnnA (HsTyVarBndr () GhcRn) -> Name
forall a. NamedThing a => a -> Name
getName GenLocated SrcSpanAnnA (HsTyVarBndr () GhcRn)
LHsTyVarBndr () GhcRn
b
              tcb :: TyConBinder
tcb = ArgFlag -> TyVar -> TyConBinder
mkNamedTyConBinder ArgFlag
Required TyVar
v
          in (TyConBinder
tcb, [(Name
v_name, TyVar
v)])

      -- 'zipBinders' does not produce any other variants of ZippedBinder.
      ZippedBinder
_ -> String
-> IOEnv (Env TcGblEnv TcLclEnv) (TyConBinder, [(Name, TyVar)])
forall a. String -> a
panic String
"goVis: invalid ZippedBinder"

    -- Given an invisible binder that comes from 'split_invis',
    -- convert it to TyConBinder.
    invis_to_tcb :: TyCoBinder -> TcM TyConBinder
    invis_to_tcb :: TyBinder -> IOEnv (Env TcGblEnv TcLclEnv) TyConBinder
invis_to_tcb TyBinder
tb = do
      (TyConBinder
tcb, [(Name, TyVar)]
stv) <- ZippedBinder
-> IOEnv (Env TcGblEnv TcLclEnv) (TyConBinder, [(Name, TyVar)])
zipped_to_tcb (TyBinder -> Maybe (LHsTyVarBndr () GhcRn) -> ZippedBinder
ZippedBinder TyBinder
tb Maybe (LHsTyVarBndr () GhcRn)
forall a. Maybe a
Nothing)
      MASSERT(null stv)
      TyConBinder -> IOEnv (Env TcGblEnv TcLclEnv) TyConBinder
forall (m :: * -> *) a. Monad m => a -> m a
return TyConBinder
tcb

    -- Check that the inline kind annotation on a binder is valid
    -- by unifying it with the kind of the quantifier.
    check_zipped_binder :: ZippedBinder -> TcM ()
    check_zipped_binder :: ZippedBinder -> TcM ()
check_zipped_binder (ZippedBinder TyBinder
_ Maybe (LHsTyVarBndr () GhcRn)
Nothing) = () -> TcM ()
forall (m :: * -> *) a. Monad m => a -> m a
return ()
    check_zipped_binder (ZippedBinder TyBinder
tb (Just LHsTyVarBndr () GhcRn
b)) =
      case GenLocated SrcSpanAnnA (HsTyVarBndr () GhcRn)
-> HsTyVarBndr () GhcRn
forall l e. GenLocated l e -> e
unLoc GenLocated SrcSpanAnnA (HsTyVarBndr () GhcRn)
LHsTyVarBndr () GhcRn
b of
        UserTyVar XUserTyVar GhcRn
_ ()
_ LIdP GhcRn
_ -> () -> TcM ()
forall (m :: * -> *) a. Monad m => a -> m a
return ()
        KindedTyVar XKindedTyVar GhcRn
_ ()
_ LIdP GhcRn
v LHsType GhcRn
v_hs_ki -> do
          Type
v_ki <- UserTypeCtxt -> LHsType GhcRn -> TcM Type
tcLHsKindSig (Name -> UserTypeCtxt
TyVarBndrKindCtxt (GenLocated SrcSpanAnnN Name -> Name
forall l e. GenLocated l e -> e
unLoc GenLocated SrcSpanAnnN Name
LIdP GhcRn
v)) LHsType GhcRn
v_hs_ki
          TcM Coercion -> TcM ()
forall a. TcM a -> TcM ()
discardResult (TcM Coercion -> TcM ()) -> TcM Coercion -> TcM ()
forall a b. (a -> b) -> a -> b
$ -- See Note [discardResult in kcCheckDeclHeader_sig]
            Maybe SDoc -> Type -> Type -> TcM Coercion
unifyKind (SDoc -> Maybe SDoc
forall a. a -> Maybe a
Just (GenLocated SrcSpanAnnN Name -> SDoc
forall a. Outputable a => a -> SDoc
ppr GenLocated SrcSpanAnnN Name
LIdP GhcRn
v))
                      (TyBinder -> Type
tyBinderType TyBinder
tb)
                      Type
v_ki

    -- Split the invisible binders that should become a part of 'tyConBinders'
    -- rather than 'tyConResKind'.
    -- See Note [Arity inference in kcCheckDeclHeader_sig]
    split_invis :: Kind -> Maybe Kind -> ([TyCoBinder], Kind)
    split_invis :: Type -> Maybe Type -> ([TyBinder], Type)
split_invis Type
sig_ki Maybe Type
Nothing =
      -- instantiate all invisible binders
      Type -> ([TyBinder], Type)
splitInvisPiTys Type
sig_ki
    split_invis Type
sig_ki (Just Type
res_ki) =
      -- subtraction a la checkExpectedKind
      let n_res_invis_bndrs :: Arity
n_res_invis_bndrs = Type -> Arity
invisibleTyBndrCount Type
res_ki
          n_sig_invis_bndrs :: Arity
n_sig_invis_bndrs = Type -> Arity
invisibleTyBndrCount Type
sig_ki
          n_inst :: Arity
n_inst = Arity
n_sig_invis_bndrs Arity -> Arity -> Arity
forall a. Num a => a -> a -> a
- Arity
n_res_invis_bndrs
      in Arity -> Type -> ([TyBinder], Type)
splitInvisPiTysN Arity
n_inst Type
sig_ki

-- A quantifier from a kind signature zipped with a user-written binder for it.
data ZippedBinder = ZippedBinder TyBinder (Maybe (LHsTyVarBndr () GhcRn))

-- See Note [Arity inference in kcCheckDeclHeader_sig]
zipBinders
  :: Kind                      -- Kind signature
  -> [LHsTyVarBndr () GhcRn]   -- User-written binders
  -> ( [ZippedBinder]          -- Zipped binders
     , [LHsTyVarBndr () GhcRn] -- Leftover user-written binders
     , Kind )                  -- Remainder of the kind signature
zipBinders :: Type
-> [LHsTyVarBndr () GhcRn]
-> ([ZippedBinder], [LHsTyVarBndr () GhcRn], Type)
zipBinders = [ZippedBinder]
-> TCvSubst
-> Type
-> [GenLocated SrcSpanAnnA (HsTyVarBndr () GhcRn)]
-> ([ZippedBinder],
    [GenLocated SrcSpanAnnA (HsTyVarBndr () GhcRn)], Type)
zip_binders [] TCvSubst
emptyTCvSubst
  where
    -- subst: we substitute as we go, to ensure that the resulting
    -- binders in the [ZippedBndr] all have distinct uniques.
    -- If not, the TyCon may get multiple binders with the same unique,
    -- which results in chaos (see #19092,3,4)
    -- (The incoming kind might be forall k. k -> forall k. k -> Type
    --  where those two k's have the same unique. Without the substitution
    --  we'd get a repeated 'k'.)
    zip_binders :: [ZippedBinder]
-> TCvSubst
-> Type
-> [GenLocated SrcSpanAnnA (HsTyVarBndr () GhcRn)]
-> ([ZippedBinder],
    [GenLocated SrcSpanAnnA (HsTyVarBndr () GhcRn)], Type)
zip_binders [ZippedBinder]
acc TCvSubst
subst Type
ki [GenLocated SrcSpanAnnA (HsTyVarBndr () GhcRn)]
bs
      | (GenLocated SrcSpanAnnA (HsTyVarBndr () GhcRn)
b:[GenLocated SrcSpanAnnA (HsTyVarBndr () GhcRn)]
bs') <- [GenLocated SrcSpanAnnA (HsTyVarBndr () GhcRn)]
bs  -- Stop as soon as 'bs' becomes empty
      , Just (TyBinder
tb,Type
ki') <- Type -> Maybe (TyBinder, Type)
tcSplitPiTy_maybe Type
ki
      , let (TCvSubst
subst', TyBinder
tb') = TCvSubst -> TyBinder -> (TCvSubst, TyBinder)
substTyCoBndr TCvSubst
subst TyBinder
tb
      = if TyBinder -> Bool
isInvisibleBinder TyBinder
tb
        then [ZippedBinder]
-> TCvSubst
-> Type
-> [GenLocated SrcSpanAnnA (HsTyVarBndr () GhcRn)]
-> ([ZippedBinder],
    [GenLocated SrcSpanAnnA (HsTyVarBndr () GhcRn)], Type)
zip_binders (TyBinder -> Maybe (LHsTyVarBndr () GhcRn) -> ZippedBinder
ZippedBinder TyBinder
tb' Maybe (LHsTyVarBndr () GhcRn)
forall a. Maybe a
Nothing  ZippedBinder -> [ZippedBinder] -> [ZippedBinder]
forall a. a -> [a] -> [a]
: [ZippedBinder]
acc) TCvSubst
subst' Type
ki' [GenLocated SrcSpanAnnA (HsTyVarBndr () GhcRn)]
bs
        else [ZippedBinder]
-> TCvSubst
-> Type
-> [GenLocated SrcSpanAnnA (HsTyVarBndr () GhcRn)]
-> ([ZippedBinder],
    [GenLocated SrcSpanAnnA (HsTyVarBndr () GhcRn)], Type)
zip_binders (TyBinder -> Maybe (LHsTyVarBndr () GhcRn) -> ZippedBinder
ZippedBinder TyBinder
tb' (GenLocated SrcSpanAnnA (HsTyVarBndr () GhcRn)
-> Maybe (GenLocated SrcSpanAnnA (HsTyVarBndr () GhcRn))
forall a. a -> Maybe a
Just GenLocated SrcSpanAnnA (HsTyVarBndr () GhcRn)
b) ZippedBinder -> [ZippedBinder] -> [ZippedBinder]
forall a. a -> [a] -> [a]
: [ZippedBinder]
acc) TCvSubst
subst' Type
ki' [GenLocated SrcSpanAnnA (HsTyVarBndr () GhcRn)]
bs'

      | Bool
otherwise
      = ([ZippedBinder] -> [ZippedBinder]
forall a. [a] -> [a]
reverse [ZippedBinder]
acc, [GenLocated SrcSpanAnnA (HsTyVarBndr () GhcRn)]
bs, HasCallStack => TCvSubst -> Type -> Type
TCvSubst -> Type -> Type
substTy TCvSubst
subst Type
ki)

tooManyBindersErr :: Kind -> [LHsTyVarBndr () GhcRn] -> SDoc
tooManyBindersErr :: Type -> [LHsTyVarBndr () GhcRn] -> SDoc
tooManyBindersErr Type
ki [LHsTyVarBndr () GhcRn]
bndrs =
   SDoc -> Arity -> SDoc -> SDoc
hang (String -> SDoc
text String
"Not a function kind:")
      Arity
4 (Type -> SDoc
forall a. Outputable a => a -> SDoc
ppr Type
ki) SDoc -> SDoc -> SDoc
$$
   SDoc -> Arity -> SDoc -> SDoc
hang (String -> SDoc
text String
"but extra binders found:")
      Arity
4 ([SDoc] -> SDoc
fsep ((GenLocated SrcSpanAnnA (HsTyVarBndr () GhcRn) -> SDoc)
-> [GenLocated SrcSpanAnnA (HsTyVarBndr () GhcRn)] -> [SDoc]
forall a b. (a -> b) -> [a] -> [b]
map GenLocated SrcSpanAnnA (HsTyVarBndr () GhcRn) -> SDoc
forall a. Outputable a => a -> SDoc
ppr [GenLocated SrcSpanAnnA (HsTyVarBndr () GhcRn)]
[LHsTyVarBndr () GhcRn]
bndrs))

{- Note [Arity inference in kcCheckDeclHeader_sig]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Given a kind signature 'kisig' and a declaration header, kcCheckDeclHeader_sig
verifies that the declaration conforms to the signature. The end result is a
TcTyCon 'tc' such that:

  tyConKind tc == kisig

This TcTyCon would be rather easy to produce if we didn't have to worry about
arity. Consider these declarations:

  type family S1 :: forall k. k -> Type
  type family S2 (a :: k) :: Type

Both S1 and S2 can be given the same standalone kind signature:

  type S2 :: forall k. k -> Type

And, indeed, tyConKind S1 == tyConKind S2. However, tyConKind is built from
tyConBinders and tyConResKind, such that

  tyConKind tc == mkTyConKind (tyConBinders tc) (tyConResKind tc)

For S1 and S2, tyConBinders and tyConResKind are different:

  tyConBinders S1  ==  []
  tyConResKind S1  ==  forall k. k -> Type
  tyConKind    S1  ==  forall k. k -> Type

  tyConBinders S2  ==  [spec k, anon-vis (a :: k)]
  tyConResKind S2  ==  Type
  tyConKind    S1  ==  forall k. k -> Type

This difference determines the arity:

  tyConArity tc == length (tyConBinders tc)

That is, the arity of S1 is 0, while the arity of S2 is 2.

'kcCheckDeclHeader_sig' needs to infer the desired arity to split the standalone
kind signature into binders and the result kind. It does so in two rounds:

1. zip user-written binders (vis_tcbs)
2. split off invisible binders (invis_tcbs)

Consider the following declarations:

    type F :: Type -> forall j. j -> forall k1 k2. (k1, k2) -> Type
    type family F a b

    type G :: Type -> forall j. j -> forall k1 k2. (k1, k2) -> Type
    type family G a b :: forall r2. (r1, r2) -> Type

In step 1 (zip user-written binders), we zip the quantifiers in the signature
with the binders in the header using 'zipBinders'. In both F and G, this results in
the following zipped binders:

                   TyBinder     LHsTyVarBndr
    ---------------------------------------
    ZippedBinder   Type ->      a
    ZippedBinder   forall j.
    ZippedBinder   j ->         b


At this point, we have accumulated three zipped binders which correspond to a
prefix of the standalone kind signature:

  Type -> forall j. j -> ...

In step 2 (split off invisible binders), we have to decide how much remaining
invisible binders of the standalone kind signature to split off:

    forall k1 k2. (k1, k2) -> Type
    ^^^^^^^^^^^^^
    split off or not?

This decision is made in 'split_invis':

* If a user-written result kind signature is not provided, as in F,
  then split off all invisible binders. This is why we need special treatment
  for AnyKind.
* If a user-written result kind signature is provided, as in G,
  then do as checkExpectedKind does and split off (n_sig - n_res) binders.
  That is, split off such an amount of binders that the remainder of the
  standalone kind signature and the user-written result kind signature have the
  same amount of invisible quantifiers.

For F, split_invis splits away all invisible binders, and we have 2:

    forall k1 k2. (k1, k2) -> Type
    ^^^^^^^^^^^^^
    split away both binders

The resulting arity of F is 3+2=5.  (length vis_tcbs = 3,
                                     length invis_tcbs = 2,
                                     length tcbs = 5)

For G, split_invis decides to split off 1 invisible binder, so that we have the
same amount of invisible quantifiers left:

    res_ki  =  forall    r2. (r1, r2) -> Type
    kisig   =  forall k1 k2. (k1, k2) -> Type
                     ^^^
                     split off this one.

The resulting arity of G is 3+1=4. (length vis_tcbs = 3,
                                    length invis_tcbs = 1,
                                    length tcbs = 4)

-}

{- Note [discardResult in kcCheckDeclHeader_sig]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
We use 'unifyKind' to check inline kind annotations in declaration headers
against the signature.

  type T :: [i] -> Maybe j -> Type
  data T (a :: [k1]) (b :: Maybe k2) :: Type where ...

Here, we will unify:

       [k1] ~ [i]
  Maybe k2  ~ Maybe j
      Type  ~ Type

The end result is that we fill in unification variables k1, k2:

    k1  :=  i
    k2  :=  j

We also validate that the user isn't confused:

  type T :: Type -> Type
  data T (a :: Bool) = ...

This will report that (Type ~ Bool) failed to unify.

Now, consider the following example:

  type family Id a where Id x = x
  type T :: Bool -> Type
  type T (a :: Id Bool) = ...

We will unify (Bool ~ Id Bool), and this will produce a non-reflexive coercion.
However, we are free to discard it, as the kind of 'T' is determined by the
signature, not by the inline kind annotation:

      we have   T ::    Bool -> Type
  rather than   T :: Id Bool -> Type

This (Id Bool) will not show up anywhere after we're done validating it, so we
have no use for the produced coercion.
-}

{- Note [No polymorphic recursion]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Should this kind-check?
  data T ka (a::ka) b  = MkT (T Type           Int   Bool)
                             (T (Type -> Type) Maybe Bool)

Notice that T is used at two different kinds in its RHS.  No!
This should not kind-check.  Polymorphic recursion is known to
be a tough nut.

Previously, we laboriously (with help from the renamer)
tried to give T the polymorphic kind
   T :: forall ka -> ka -> kappa -> Type
where kappa is a unification variable, even in the inferInitialKinds
phase (which is what kcInferDeclHeader is all about).  But
that is dangerously fragile (see the ticket).

Solution: make kcInferDeclHeader give T a straightforward
monomorphic kind, with no quantification whatsoever. That's why
we use mkAnonTyConBinder for all arguments when figuring out
tc_binders.

But notice that (#16322 comment:3)

* The algorithm successfully kind-checks this declaration:
    data T2 ka (a::ka) = MkT2 (T2 Type a)

  Starting with (inferInitialKinds)
    T2 :: (kappa1 :: kappa2 :: *) -> (kappa3 :: kappa4 :: *) -> *
  we get
    kappa4 := kappa1   -- from the (a:ka) kind signature
    kappa1 := Type     -- From application T2 Type

  These constraints are soluble so generaliseTcTyCon gives
    T2 :: forall (k::Type) -> k -> *

  But now the /typechecking/ (aka desugaring, tcTyClDecl) phase
  fails, because the call (T2 Type a) in the RHS is ill-kinded.

  We'd really prefer all errors to show up in the kind checking
  phase.

* This algorithm still accepts (in all phases)
     data T3 ka (a::ka) = forall b. MkT3 (T3 Type b)
  although T3 is really polymorphic-recursive too.
  Perhaps we should somehow reject that.

Note [Kind variable ordering for associated types]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
What should be the kind of `T` in the following example? (#15591)

  class C (a :: Type) where
    type T (x :: f a)

As per Note [Ordering of implicit variables] in GHC.Rename.HsType, we want to quantify
the kind variables in left-to-right order of first occurrence in order to
support visible kind application. But we cannot perform this analysis on just
T alone, since its variable `a` actually occurs /before/ `f` if you consider
the fact that `a` was previously bound by the parent class `C`. That is to say,
the kind of `T` should end up being:

  T :: forall a f. f a -> Type

(It wouldn't necessarily be /wrong/ if the kind ended up being, say,
forall f a. f a -> Type, but that would not be as predictable for users of
visible kind application.)

In contrast, if `T` were redefined to be a top-level type family, like `T2`
below:

  type family T2 (x :: f (a :: Type))

Then `a` first appears /after/ `f`, so the kind of `T2` should be:

  T2 :: forall f a. f a -> Type

In order to make this distinction, we need to know (in kcCheckDeclHeader) which
type variables have been bound by the parent class (if there is one). With
the class-bound variables in hand, we can ensure that we always quantify
these first.
-}


{- *********************************************************************
*                                                                      *
             Expected kinds
*                                                                      *
********************************************************************* -}

-- | Describes the kind expected in a certain context.
data ContextKind = TheKind Kind   -- ^ a specific kind
                 | AnyKind        -- ^ any kind will do
                 | OpenKind       -- ^ something of the form @TYPE _@

-----------------------
newExpectedKind :: ContextKind -> TcM Kind
newExpectedKind :: ContextKind -> TcM Type
newExpectedKind (TheKind Type
k)   = Type -> TcM Type
forall (m :: * -> *) a. Monad m => a -> m a
return Type
k
newExpectedKind ContextKind
AnyKind       = TcM Type
newMetaKindVar
newExpectedKind ContextKind
OpenKind      = TcM Type
newOpenTypeKind

-----------------------
expectedKindInCtxt :: UserTypeCtxt -> ContextKind
-- Depending on the context, we might accept any kind (for instance, in a TH
-- splice), or only certain kinds (like in type signatures).
expectedKindInCtxt :: UserTypeCtxt -> ContextKind
expectedKindInCtxt (TySynCtxt Name
_)   = ContextKind
AnyKind
expectedKindInCtxt (GhciCtxt {})   = ContextKind
AnyKind
-- The types in a 'default' decl can have varying kinds
-- See Note [Extended defaults]" in GHC.Tc.Utils.Env
expectedKindInCtxt UserTypeCtxt
DefaultDeclCtxt     = ContextKind
AnyKind
expectedKindInCtxt UserTypeCtxt
DerivClauseCtxt     = ContextKind
AnyKind
expectedKindInCtxt UserTypeCtxt
TypeAppCtxt         = ContextKind
AnyKind
expectedKindInCtxt (ForSigCtxt Name
_)      = Type -> ContextKind
TheKind Type
liftedTypeKind
expectedKindInCtxt (InstDeclCtxt {})   = Type -> ContextKind
TheKind Type
constraintKind
expectedKindInCtxt UserTypeCtxt
SpecInstCtxt        = Type -> ContextKind
TheKind Type
constraintKind
expectedKindInCtxt UserTypeCtxt
_                   = ContextKind
OpenKind


{- *********************************************************************
*                                                                      *
             Bringing type variables into scope
*                                                                      *
********************************************************************* -}

--------------------------------------
--    HsForAllTelescope
--------------------------------------

tcTKTelescope :: TcTyMode
              -> HsForAllTelescope GhcRn
              -> TcM a
              -> TcM ([TcTyVarBinder], a)
tcTKTelescope :: forall a.
TcTyMode
-> HsForAllTelescope GhcRn -> TcM a -> TcM ([TcTyVarBinder], a)
tcTKTelescope TcTyMode
mode HsForAllTelescope GhcRn
tele TcM a
thing_inside = case HsForAllTelescope GhcRn
tele of
  HsForAllVis { hsf_vis_bndrs :: forall pass. HsForAllTelescope pass -> [LHsTyVarBndr () pass]
hsf_vis_bndrs = [LHsTyVarBndr () GhcRn]
bndrs }
    -> do { ([VarBndr TyVar ()]
req_tv_bndrs, a
thing) <- SkolemMode
-> [LHsTyVarBndr () GhcRn] -> TcM a -> TcM ([VarBndr TyVar ()], a)
forall flag a.
OutputableBndrFlag flag 'Renamed =>
SkolemMode
-> [LHsTyVarBndr flag GhcRn]
-> TcM a
-> TcM ([VarBndr TyVar flag], a)
tcExplicitTKBndrsX SkolemMode
skol_mode [LHsTyVarBndr () GhcRn]
bndrs TcM a
thing_inside
            -- req_tv_bndrs :: [VarBndr TyVar ()],
            -- but we want [VarBndr TyVar ArgFlag]
          ; ([TcTyVarBinder], a) -> TcM ([TcTyVarBinder], a)
forall (m :: * -> *) a. Monad m => a -> m a
return ([VarBndr TyVar ()] -> [TcTyVarBinder]
forall a. [VarBndr a ()] -> [VarBndr a ArgFlag]
tyVarReqToBinders [VarBndr TyVar ()]
req_tv_bndrs, a
thing) }

  HsForAllInvis { hsf_invis_bndrs :: forall pass.
HsForAllTelescope pass -> [LHsTyVarBndr Specificity pass]
hsf_invis_bndrs = [LHsTyVarBndr Specificity GhcRn]
bndrs }
    -> do { ([InvisTVBinder]
inv_tv_bndrs, a
thing) <- SkolemMode
-> [LHsTyVarBndr Specificity GhcRn]
-> TcM a
-> TcM ([InvisTVBinder], a)
forall flag a.
OutputableBndrFlag flag 'Renamed =>
SkolemMode
-> [LHsTyVarBndr flag GhcRn]
-> TcM a
-> TcM ([VarBndr TyVar flag], a)
tcExplicitTKBndrsX SkolemMode
skol_mode [LHsTyVarBndr Specificity GhcRn]
bndrs TcM a
thing_inside
            -- inv_tv_bndrs :: [VarBndr TyVar Specificity],
            -- but we want [VarBndr TyVar ArgFlag]
          ; ([TcTyVarBinder], a) -> TcM ([TcTyVarBinder], a)
forall (m :: * -> *) a. Monad m => a -> m a
return ([InvisTVBinder] -> [TcTyVarBinder]
forall a. [VarBndr a Specificity] -> [VarBndr a ArgFlag]
tyVarSpecToBinders [InvisTVBinder]
inv_tv_bndrs, a
thing) }
  where
    skol_mode :: SkolemMode
skol_mode = SkolemMode
smVanilla { sm_clone :: Bool
sm_clone = Bool
False, sm_holes :: HoleInfo
sm_holes = TcTyMode -> HoleInfo
mode_holes TcTyMode
mode }

--------------------------------------
--    HsOuterTyVarBndrs
--------------------------------------

bindOuterTKBndrsX :: OutputableBndrFlag flag 'Renamed
                  => SkolemMode
                  -> HsOuterTyVarBndrs flag GhcRn
                  -> TcM a
                  -> TcM (HsOuterTyVarBndrs flag GhcTc, a)
bindOuterTKBndrsX :: forall flag a.
OutputableBndrFlag flag 'Renamed =>
SkolemMode
-> HsOuterTyVarBndrs flag GhcRn
-> TcM a
-> TcM (HsOuterTyVarBndrs flag GhcTc, a)
bindOuterTKBndrsX SkolemMode
skol_mode HsOuterTyVarBndrs flag GhcRn
outer_bndrs TcM a
thing_inside
  = case HsOuterTyVarBndrs flag GhcRn
outer_bndrs of
      HsOuterImplicit{hso_ximplicit :: forall flag pass.
HsOuterTyVarBndrs flag pass -> XHsOuterImplicit pass
hso_ximplicit = XHsOuterImplicit GhcRn
imp_tvs} ->
        do { ([TyVar]
imp_tvs', a
thing) <- SkolemMode -> HsQTvsRn -> TcM a -> TcM ([TyVar], a)
forall a. SkolemMode -> HsQTvsRn -> TcM a -> TcM ([TyVar], a)
bindImplicitTKBndrsX SkolemMode
skol_mode HsQTvsRn
XHsOuterImplicit GhcRn
imp_tvs TcM a
thing_inside
           ; (HsOuterTyVarBndrs flag GhcTc, a)
-> TcM (HsOuterTyVarBndrs flag GhcTc, a)
forall (m :: * -> *) a. Monad m => a -> m a
return ( HsOuterImplicit{hso_ximplicit :: XHsOuterImplicit GhcTc
hso_ximplicit = [TyVar]
XHsOuterImplicit GhcTc
imp_tvs'}
                    , a
thing) }
      HsOuterExplicit{hso_bndrs :: forall flag pass.
HsOuterTyVarBndrs flag pass -> [LHsTyVarBndr flag (NoGhcTc pass)]
hso_bndrs = [LHsTyVarBndr flag (NoGhcTc GhcRn)]
exp_bndrs} ->
        do { ([VarBndr TyVar flag]
exp_tvs', a
thing) <- SkolemMode
-> [LHsTyVarBndr flag GhcRn]
-> TcM a
-> TcM ([VarBndr TyVar flag], a)
forall flag a.
OutputableBndrFlag flag 'Renamed =>
SkolemMode
-> [LHsTyVarBndr flag GhcRn]
-> TcM a
-> TcM ([VarBndr TyVar flag], a)
bindExplicitTKBndrsX SkolemMode
skol_mode [LHsTyVarBndr flag (NoGhcTc GhcRn)]
[LHsTyVarBndr flag GhcRn]
exp_bndrs TcM a
thing_inside
           ; (HsOuterTyVarBndrs flag GhcTc, a)
-> TcM (HsOuterTyVarBndrs flag GhcTc, a)
forall (m :: * -> *) a. Monad m => a -> m a
return ( HsOuterExplicit { hso_xexplicit :: XHsOuterExplicit GhcTc flag
hso_xexplicit = [VarBndr TyVar flag]
XHsOuterExplicit GhcTc flag
exp_tvs'
                                      , hso_bndrs :: [LHsTyVarBndr flag (NoGhcTc GhcTc)]
hso_bndrs     = [LHsTyVarBndr flag (NoGhcTc GhcRn)]
[LHsTyVarBndr flag (NoGhcTc GhcTc)]
exp_bndrs }
                    , a
thing) }

getOuterTyVars :: HsOuterTyVarBndrs flag GhcTc -> [TcTyVar]
-- The returned [TcTyVar] is not necessarily in dependency order
-- at least for the HsOuterImplicit case
getOuterTyVars :: forall flag. HsOuterTyVarBndrs flag GhcTc -> [TyVar]
getOuterTyVars (HsOuterImplicit { hso_ximplicit :: forall flag pass.
HsOuterTyVarBndrs flag pass -> XHsOuterImplicit pass
hso_ximplicit = XHsOuterImplicit GhcTc
tvs })  = [TyVar]
XHsOuterImplicit GhcTc
tvs
getOuterTyVars (HsOuterExplicit { hso_xexplicit :: forall flag pass.
HsOuterTyVarBndrs flag pass -> XHsOuterExplicit pass flag
hso_xexplicit = XHsOuterExplicit GhcTc flag
tvbs }) = [VarBndr TyVar flag] -> [TyVar]
forall tv argf. [VarBndr tv argf] -> [tv]
binderVars [VarBndr TyVar flag]
XHsOuterExplicit GhcTc flag
tvbs

---------------
scopedSortOuter :: HsOuterTyVarBndrs Specificity GhcTc -> TcM [InvisTVBinder]
-- Sort any /implicit/ binders into dependency order
--     (zonking first so we can see the dependencies)
-- /Explicit/ ones are already in the right order
scopedSortOuter :: HsOuterTyVarBndrs Specificity GhcTc -> TcM [InvisTVBinder]
scopedSortOuter (HsOuterImplicit{hso_ximplicit :: forall flag pass.
HsOuterTyVarBndrs flag pass -> XHsOuterImplicit pass
hso_ximplicit = XHsOuterImplicit GhcTc
imp_tvs})
  = do { [TyVar]
imp_tvs <- [TyVar] -> TcM [TyVar]
zonkAndScopedSort [TyVar]
XHsOuterImplicit GhcTc
imp_tvs
       ; [InvisTVBinder] -> TcM [InvisTVBinder]
forall (m :: * -> *) a. Monad m => a -> m a
return [TyVar -> Specificity -> InvisTVBinder
forall var argf. var -> argf -> VarBndr var argf
Bndr TyVar
tv Specificity
SpecifiedSpec | TyVar
tv <- [TyVar]
imp_tvs] }
scopedSortOuter (HsOuterExplicit{hso_xexplicit :: forall flag pass.
HsOuterTyVarBndrs flag pass -> XHsOuterExplicit pass flag
hso_xexplicit = XHsOuterExplicit GhcTc Specificity
exp_tvs})
  = -- No need to dependency-sort (or zonk) explicit quantifiers
    [InvisTVBinder] -> TcM [InvisTVBinder]
forall (m :: * -> *) a. Monad m => a -> m a
return [InvisTVBinder]
XHsOuterExplicit GhcTc Specificity
exp_tvs

---------------
bindOuterSigTKBndrs_Tv :: HsOuterSigTyVarBndrs GhcRn
                       -> TcM a -> TcM (HsOuterSigTyVarBndrs GhcTc, a)
bindOuterSigTKBndrs_Tv :: forall a.
HsOuterSigTyVarBndrs GhcRn
-> TcM a -> TcM (HsOuterTyVarBndrs Specificity GhcTc, a)
bindOuterSigTKBndrs_Tv
  = SkolemMode
-> HsOuterSigTyVarBndrs GhcRn
-> TcM a
-> TcM (HsOuterTyVarBndrs Specificity GhcTc, a)
forall flag a.
OutputableBndrFlag flag 'Renamed =>
SkolemMode
-> HsOuterTyVarBndrs flag GhcRn
-> TcM a
-> TcM (HsOuterTyVarBndrs flag GhcTc, a)
bindOuterTKBndrsX (SkolemMode
smVanilla { sm_clone :: Bool
sm_clone = Bool
True, sm_tvtv :: Bool
sm_tvtv = Bool
True })

bindOuterSigTKBndrs_Tv_M :: TcTyMode
                         -> HsOuterSigTyVarBndrs GhcRn
                         -> TcM a -> TcM (HsOuterSigTyVarBndrs GhcTc, a)
-- Do not push level; do not make implication constraint; use Tvs
-- Two major clients of this "bind-only" path are:
--    Note [Using TyVarTvs for kind-checking GADTs] in GHC.Tc.TyCl
--    Note [Checking partial type signatures]
bindOuterSigTKBndrs_Tv_M :: forall a.
TcTyMode
-> HsOuterSigTyVarBndrs GhcRn
-> TcM a
-> TcM (HsOuterTyVarBndrs Specificity GhcTc, a)
bindOuterSigTKBndrs_Tv_M TcTyMode
mode
  = SkolemMode
-> HsOuterSigTyVarBndrs GhcRn
-> TcM a
-> TcM (HsOuterTyVarBndrs Specificity GhcTc, a)
forall flag a.
OutputableBndrFlag flag 'Renamed =>
SkolemMode
-> HsOuterTyVarBndrs flag GhcRn
-> TcM a
-> TcM (HsOuterTyVarBndrs flag GhcTc, a)
bindOuterTKBndrsX (SkolemMode
smVanilla { sm_clone :: Bool
sm_clone = Bool
True, sm_tvtv :: Bool
sm_tvtv = Bool
True
                                 , sm_holes :: HoleInfo
sm_holes = TcTyMode -> HoleInfo
mode_holes TcTyMode
mode })

bindOuterFamEqnTKBndrs_Q_Tv :: HsOuterFamEqnTyVarBndrs GhcRn
                            -> TcM a
                            -> TcM ([TcTyVar], a)
bindOuterFamEqnTKBndrs_Q_Tv :: forall a.
HsOuterFamEqnTyVarBndrs GhcRn -> TcM a -> TcM ([TyVar], a)
bindOuterFamEqnTKBndrs_Q_Tv HsOuterFamEqnTyVarBndrs GhcRn
hs_bndrs TcM a
thing_inside
  = (HsOuterTyVarBndrs () GhcTc -> [TyVar])
-> IOEnv (Env TcGblEnv TcLclEnv) (HsOuterTyVarBndrs () GhcTc, a)
-> IOEnv (Env TcGblEnv TcLclEnv) ([TyVar], a)
forall (m :: * -> *) a b r.
Monad m =>
(a -> b) -> m (a, r) -> m (b, r)
liftFstM HsOuterTyVarBndrs () GhcTc -> [TyVar]
forall flag. HsOuterTyVarBndrs flag GhcTc -> [TyVar]
getOuterTyVars (IOEnv (Env TcGblEnv TcLclEnv) (HsOuterTyVarBndrs () GhcTc, a)
 -> IOEnv (Env TcGblEnv TcLclEnv) ([TyVar], a))
-> IOEnv (Env TcGblEnv TcLclEnv) (HsOuterTyVarBndrs () GhcTc, a)
-> IOEnv (Env TcGblEnv TcLclEnv) ([TyVar], a)
forall a b. (a -> b) -> a -> b
$
    SkolemMode
-> HsOuterFamEqnTyVarBndrs GhcRn
-> TcM a
-> IOEnv (Env TcGblEnv TcLclEnv) (HsOuterTyVarBndrs () GhcTc, a)
forall flag a.
OutputableBndrFlag flag 'Renamed =>
SkolemMode
-> HsOuterTyVarBndrs flag GhcRn
-> TcM a
-> TcM (HsOuterTyVarBndrs flag GhcTc, a)
bindOuterTKBndrsX (SkolemMode
smVanilla { sm_clone :: Bool
sm_clone = Bool
False, sm_parent :: Bool
sm_parent = Bool
True
                                 , sm_tvtv :: Bool
sm_tvtv = Bool
True })
                      HsOuterFamEqnTyVarBndrs GhcRn
hs_bndrs TcM a
thing_inside
    -- sm_clone=False: see Note [Cloning for type variable binders]

bindOuterFamEqnTKBndrs :: HsOuterFamEqnTyVarBndrs GhcRn
                       -> TcM a
                       -> TcM ([TcTyVar], a)
bindOuterFamEqnTKBndrs :: forall a.
HsOuterFamEqnTyVarBndrs GhcRn -> TcM a -> TcM ([TyVar], a)
bindOuterFamEqnTKBndrs HsOuterFamEqnTyVarBndrs GhcRn
hs_bndrs TcM a
thing_inside
  = (HsOuterTyVarBndrs () GhcTc -> [TyVar])
-> IOEnv (Env TcGblEnv TcLclEnv) (HsOuterTyVarBndrs () GhcTc, a)
-> IOEnv (Env TcGblEnv TcLclEnv) ([TyVar], a)
forall (m :: * -> *) a b r.
Monad m =>
(a -> b) -> m (a, r) -> m (b, r)
liftFstM HsOuterTyVarBndrs () GhcTc -> [TyVar]
forall flag. HsOuterTyVarBndrs flag GhcTc -> [TyVar]
getOuterTyVars (IOEnv (Env TcGblEnv TcLclEnv) (HsOuterTyVarBndrs () GhcTc, a)
 -> IOEnv (Env TcGblEnv TcLclEnv) ([TyVar], a))
-> IOEnv (Env TcGblEnv TcLclEnv) (HsOuterTyVarBndrs () GhcTc, a)
-> IOEnv (Env TcGblEnv TcLclEnv) ([TyVar], a)
forall a b. (a -> b) -> a -> b
$
    SkolemMode
-> HsOuterFamEqnTyVarBndrs GhcRn
-> TcM a
-> IOEnv (Env TcGblEnv TcLclEnv) (HsOuterTyVarBndrs () GhcTc, a)
forall flag a.
OutputableBndrFlag flag 'Renamed =>
SkolemMode
-> HsOuterTyVarBndrs flag GhcRn
-> TcM a
-> TcM (HsOuterTyVarBndrs flag GhcTc, a)
bindOuterTKBndrsX (SkolemMode
smVanilla { sm_clone :: Bool
sm_clone = Bool
False, sm_parent :: Bool
sm_parent = Bool
True })
                      HsOuterFamEqnTyVarBndrs GhcRn
hs_bndrs TcM a
thing_inside
    -- sm_clone=False: see Note [Cloning for type variable binders]

---------------
tcOuterTKBndrs :: OutputableBndrFlag flag 'Renamed
               => SkolemInfo
               -> HsOuterTyVarBndrs flag GhcRn
               -> TcM a -> TcM (HsOuterTyVarBndrs flag GhcTc, a)
tcOuterTKBndrs :: forall flag a.
OutputableBndrFlag flag 'Renamed =>
SkolemInfo
-> HsOuterTyVarBndrs flag GhcRn
-> TcM a
-> TcM (HsOuterTyVarBndrs flag GhcTc, a)
tcOuterTKBndrs = SkolemMode
-> SkolemInfo
-> HsOuterTyVarBndrs flag GhcRn
-> TcM a
-> TcM (HsOuterTyVarBndrs flag GhcTc, a)
forall flag a.
OutputableBndrFlag flag 'Renamed =>
SkolemMode
-> SkolemInfo
-> HsOuterTyVarBndrs flag GhcRn
-> TcM a
-> TcM (HsOuterTyVarBndrs flag GhcTc, a)
tcOuterTKBndrsX (SkolemMode
smVanilla { sm_clone :: Bool
sm_clone = Bool
False })
  -- Do not clone the outer binders
  -- See Note [Cloning for type variable binder] under "must not"

tcOuterTKBndrsX :: OutputableBndrFlag flag 'Renamed
                => SkolemMode -> SkolemInfo
                -> HsOuterTyVarBndrs flag GhcRn
                -> TcM a -> TcM (HsOuterTyVarBndrs flag GhcTc, a)
-- Push level, capture constraints, make implication
tcOuterTKBndrsX :: forall flag a.
OutputableBndrFlag flag 'Renamed =>
SkolemMode
-> SkolemInfo
-> HsOuterTyVarBndrs flag GhcRn
-> TcM a
-> TcM (HsOuterTyVarBndrs flag GhcTc, a)
tcOuterTKBndrsX SkolemMode
skol_mode SkolemInfo
skol_info HsOuterTyVarBndrs flag GhcRn
outer_bndrs TcM a
thing_inside
  = case HsOuterTyVarBndrs flag GhcRn
outer_bndrs of
      HsOuterImplicit{hso_ximplicit :: forall flag pass.
HsOuterTyVarBndrs flag pass -> XHsOuterImplicit pass
hso_ximplicit = XHsOuterImplicit GhcRn
imp_tvs} ->
        do { ([TyVar]
imp_tvs', a
thing) <- SkolemMode -> SkolemInfo -> HsQTvsRn -> TcM a -> TcM ([TyVar], a)
forall a.
SkolemMode -> SkolemInfo -> HsQTvsRn -> TcM a -> TcM ([TyVar], a)
tcImplicitTKBndrsX SkolemMode
skol_mode SkolemInfo
skol_info HsQTvsRn
XHsOuterImplicit GhcRn
imp_tvs TcM a
thing_inside
           ; (HsOuterTyVarBndrs flag GhcTc, a)
-> TcM (HsOuterTyVarBndrs flag GhcTc, a)
forall (m :: * -> *) a. Monad m => a -> m a
return ( HsOuterImplicit{hso_ximplicit :: XHsOuterImplicit GhcTc
hso_ximplicit = [TyVar]
XHsOuterImplicit GhcTc
imp_tvs'}
                    , a
thing) }
      HsOuterExplicit{hso_bndrs :: forall flag pass.
HsOuterTyVarBndrs flag pass -> [LHsTyVarBndr flag (NoGhcTc pass)]
hso_bndrs = [LHsTyVarBndr flag (NoGhcTc GhcRn)]
exp_bndrs} ->
        do { ([VarBndr TyVar flag]
exp_tvs', a
thing) <- SkolemMode
-> [LHsTyVarBndr flag GhcRn]
-> TcM a
-> TcM ([VarBndr TyVar flag], a)
forall flag a.
OutputableBndrFlag flag 'Renamed =>
SkolemMode
-> [LHsTyVarBndr flag GhcRn]
-> TcM a
-> TcM ([VarBndr TyVar flag], a)
tcExplicitTKBndrsX SkolemMode
skol_mode [LHsTyVarBndr flag (NoGhcTc GhcRn)]
[LHsTyVarBndr flag GhcRn]
exp_bndrs TcM a
thing_inside
           ; (HsOuterTyVarBndrs flag GhcTc, a)
-> TcM (HsOuterTyVarBndrs flag GhcTc, a)
forall (m :: * -> *) a. Monad m => a -> m a
return ( HsOuterExplicit { hso_xexplicit :: XHsOuterExplicit GhcTc flag
hso_xexplicit = [VarBndr TyVar flag]
XHsOuterExplicit GhcTc flag
exp_tvs'
                                      , hso_bndrs :: [LHsTyVarBndr flag (NoGhcTc GhcTc)]
hso_bndrs     = [LHsTyVarBndr flag (NoGhcTc GhcRn)]
[LHsTyVarBndr flag (NoGhcTc GhcTc)]
exp_bndrs }
                    , a
thing) }

--------------------------------------
--    Explicit tyvar binders
--------------------------------------

tcExplicitTKBndrs :: OutputableBndrFlag flag 'Renamed
                  => [LHsTyVarBndr flag GhcRn]
                  -> TcM a
                  -> TcM ([VarBndr TyVar flag], a)
tcExplicitTKBndrs :: forall flag a.
OutputableBndrFlag flag 'Renamed =>
[LHsTyVarBndr flag GhcRn] -> TcM a -> TcM ([VarBndr TyVar flag], a)
tcExplicitTKBndrs = SkolemMode
-> [LHsTyVarBndr flag GhcRn]
-> TcM a
-> TcM ([VarBndr TyVar flag], a)
forall flag a.
OutputableBndrFlag flag 'Renamed =>
SkolemMode
-> [LHsTyVarBndr flag GhcRn]
-> TcM a
-> TcM ([VarBndr TyVar flag], a)
tcExplicitTKBndrsX (SkolemMode
smVanilla { sm_clone :: Bool
sm_clone = Bool
True })

tcExplicitTKBndrsX :: OutputableBndrFlag flag 'Renamed
                   => SkolemMode
                   -> [LHsTyVarBndr flag GhcRn]
                   -> TcM a
                   -> TcM ([VarBndr TyVar flag], a)
-- Push level, capture constraints,
-- and emit an implication constraint with a ForAllSkol ic_info,
-- so that it is subject to a telescope test.
tcExplicitTKBndrsX :: forall flag a.
OutputableBndrFlag flag 'Renamed =>
SkolemMode
-> [LHsTyVarBndr flag GhcRn]
-> TcM a
-> TcM ([VarBndr TyVar flag], a)
tcExplicitTKBndrsX SkolemMode
skol_mode [LHsTyVarBndr flag GhcRn]
bndrs TcM a
thing_inside
  = do { (TcLevel
tclvl, WantedConstraints
wanted, ([VarBndr TyVar flag]
skol_tvs, a
res))
             <- TcM ([VarBndr TyVar flag], a)
-> TcM (TcLevel, WantedConstraints, ([VarBndr TyVar flag], a))
forall a. TcM a -> TcM (TcLevel, WantedConstraints, a)
pushLevelAndCaptureConstraints (TcM ([VarBndr TyVar flag], a)
 -> TcM (TcLevel, WantedConstraints, ([VarBndr TyVar flag], a)))
-> TcM ([VarBndr TyVar flag], a)
-> TcM (TcLevel, WantedConstraints, ([VarBndr TyVar flag], a))
forall a b. (a -> b) -> a -> b
$
                SkolemMode
-> [LHsTyVarBndr flag GhcRn]
-> TcM a
-> TcM ([VarBndr TyVar flag], a)
forall flag a.
OutputableBndrFlag flag 'Renamed =>
SkolemMode
-> [LHsTyVarBndr flag GhcRn]
-> TcM a
-> TcM ([VarBndr TyVar flag], a)
bindExplicitTKBndrsX SkolemMode
skol_mode [LHsTyVarBndr flag GhcRn]
bndrs (TcM a -> TcM ([VarBndr TyVar flag], a))
-> TcM a -> TcM ([VarBndr TyVar flag], a)
forall a b. (a -> b) -> a -> b
$
                TcM a
thing_inside

       ; let skol_info :: SkolemInfo
skol_info = SDoc -> SkolemInfo
ForAllSkol ([SDoc] -> SDoc
fsep ((GenLocated SrcSpanAnnA (HsTyVarBndr flag GhcRn) -> SDoc)
-> [GenLocated SrcSpanAnnA (HsTyVarBndr flag GhcRn)] -> [SDoc]
forall a b. (a -> b) -> [a] -> [b]
map GenLocated SrcSpanAnnA (HsTyVarBndr flag GhcRn) -> SDoc
forall a. Outputable a => a -> SDoc
ppr [GenLocated SrcSpanAnnA (HsTyVarBndr flag GhcRn)]
[LHsTyVarBndr flag GhcRn]
bndrs))
             -- Notice that we use ForAllSkol here, ignoring the enclosing
             -- skol_info unlike tc_implicit_tk_bndrs, because the bad-telescope
             -- test applies only to ForAllSkol
       ; SkolemInfo -> [TyVar] -> TcLevel -> WantedConstraints -> TcM ()
emitResidualTvConstraint SkolemInfo
skol_info ([VarBndr TyVar flag] -> [TyVar]
forall tv argf. [VarBndr tv argf] -> [tv]
binderVars [VarBndr TyVar flag]
skol_tvs) TcLevel
tclvl WantedConstraints
wanted

       ; ([VarBndr TyVar flag], a) -> TcM ([VarBndr TyVar flag], a)
forall (m :: * -> *) a. Monad m => a -> m a
return ([VarBndr TyVar flag]
skol_tvs, a
res) }

----------------
-- | Skolemise the 'HsTyVarBndr's in an 'HsForAllTelescope' with the supplied
-- 'TcTyMode'.
bindExplicitTKBndrs_Skol, bindExplicitTKBndrs_Tv
    :: (OutputableBndrFlag flag 'Renamed)
    => [LHsTyVarBndr flag GhcRn]
    -> TcM a
    -> TcM ([VarBndr TyVar flag], a)

bindExplicitTKBndrs_Skol :: forall flag a.
OutputableBndrFlag flag 'Renamed =>
[LHsTyVarBndr flag GhcRn] -> TcM a -> TcM ([VarBndr TyVar flag], a)
bindExplicitTKBndrs_Skol = SkolemMode
-> [LHsTyVarBndr flag GhcRn]
-> TcM a
-> TcM ([VarBndr TyVar flag], a)
forall flag a.
OutputableBndrFlag flag 'Renamed =>
SkolemMode
-> [LHsTyVarBndr flag GhcRn]
-> TcM a
-> TcM ([VarBndr TyVar flag], a)
bindExplicitTKBndrsX (SkolemMode
smVanilla { sm_clone :: Bool
sm_clone = Bool
False })
bindExplicitTKBndrs_Tv :: forall flag a.
OutputableBndrFlag flag 'Renamed =>
[LHsTyVarBndr flag GhcRn] -> TcM a -> TcM ([VarBndr TyVar flag], a)
bindExplicitTKBndrs_Tv   = SkolemMode
-> [LHsTyVarBndr flag GhcRn]
-> TcM a
-> TcM ([VarBndr TyVar flag], a)
forall flag a.
OutputableBndrFlag flag 'Renamed =>
SkolemMode
-> [LHsTyVarBndr flag GhcRn]
-> TcM a
-> TcM ([VarBndr TyVar flag], a)
bindExplicitTKBndrsX (SkolemMode
smVanilla { sm_clone :: Bool
sm_clone = Bool
True, sm_tvtv :: Bool
sm_tvtv = Bool
True })
   -- sm_clone: see Note [Cloning for type variable binders]

bindExplicitTKBndrs_Q_Skol, bindExplicitTKBndrs_Q_Tv
    :: ContextKind
    -> [LHsTyVarBndr () GhcRn]
    -> TcM a
    -> TcM ([TcTyVar], a)
-- These do not clone: see Note [Cloning for type variable binders]
bindExplicitTKBndrs_Q_Skol :: forall a.
ContextKind -> [LHsTyVarBndr () GhcRn] -> TcM a -> TcM ([TyVar], a)
bindExplicitTKBndrs_Q_Skol ContextKind
ctxt_kind [LHsTyVarBndr () GhcRn]
hs_bndrs TcM a
thing_inside
  = ([VarBndr TyVar ()] -> [TyVar])
-> IOEnv (Env TcGblEnv TcLclEnv) ([VarBndr TyVar ()], a)
-> IOEnv (Env TcGblEnv TcLclEnv) ([TyVar], a)
forall (m :: * -> *) a b r.
Monad m =>
(a -> b) -> m (a, r) -> m (b, r)
liftFstM [VarBndr TyVar ()] -> [TyVar]
forall tv argf. [VarBndr tv argf] -> [tv]
binderVars (IOEnv (Env TcGblEnv TcLclEnv) ([VarBndr TyVar ()], a)
 -> IOEnv (Env TcGblEnv TcLclEnv) ([TyVar], a))
-> IOEnv (Env TcGblEnv TcLclEnv) ([VarBndr TyVar ()], a)
-> IOEnv (Env TcGblEnv TcLclEnv) ([TyVar], a)
forall a b. (a -> b) -> a -> b
$
    SkolemMode
-> [LHsTyVarBndr () GhcRn]
-> TcM a
-> IOEnv (Env TcGblEnv TcLclEnv) ([VarBndr TyVar ()], a)
forall flag a.
OutputableBndrFlag flag 'Renamed =>
SkolemMode
-> [LHsTyVarBndr flag GhcRn]
-> TcM a
-> TcM ([VarBndr TyVar flag], a)
bindExplicitTKBndrsX (SkolemMode
smVanilla { sm_clone :: Bool
sm_clone = Bool
False, sm_parent :: Bool
sm_parent = Bool
True
                                    , sm_kind :: ContextKind
sm_kind = ContextKind
ctxt_kind })
                         [LHsTyVarBndr () GhcRn]
hs_bndrs TcM a
thing_inside
    -- sm_clone=False: see Note [Cloning for type variable binders]

bindExplicitTKBndrs_Q_Tv :: forall a.
ContextKind -> [LHsTyVarBndr () GhcRn] -> TcM a -> TcM ([TyVar], a)
bindExplicitTKBndrs_Q_Tv ContextKind
ctxt_kind [LHsTyVarBndr () GhcRn]
hs_bndrs TcM a
thing_inside
  = ([VarBndr TyVar ()] -> [TyVar])
-> IOEnv (Env TcGblEnv TcLclEnv) ([VarBndr TyVar ()], a)
-> IOEnv (Env TcGblEnv TcLclEnv) ([TyVar], a)
forall (m :: * -> *) a b r.
Monad m =>
(a -> b) -> m (a, r) -> m (b, r)
liftFstM [VarBndr TyVar ()] -> [TyVar]
forall tv argf. [VarBndr tv argf] -> [tv]
binderVars (IOEnv (Env TcGblEnv TcLclEnv) ([VarBndr TyVar ()], a)
 -> IOEnv (Env TcGblEnv TcLclEnv) ([TyVar], a))
-> IOEnv (Env TcGblEnv TcLclEnv) ([VarBndr TyVar ()], a)
-> IOEnv (Env TcGblEnv TcLclEnv) ([TyVar], a)
forall a b. (a -> b) -> a -> b
$
    SkolemMode
-> [LHsTyVarBndr () GhcRn]
-> TcM a
-> IOEnv (Env TcGblEnv TcLclEnv) ([VarBndr TyVar ()], a)
forall flag a.
OutputableBndrFlag flag 'Renamed =>
SkolemMode
-> [LHsTyVarBndr flag GhcRn]
-> TcM a
-> TcM ([VarBndr TyVar flag], a)
bindExplicitTKBndrsX (SkolemMode
smVanilla { sm_clone :: Bool
sm_clone = Bool
False, sm_parent :: Bool
sm_parent = Bool
True
                                    , sm_tvtv :: Bool
sm_tvtv = Bool
True, sm_kind :: ContextKind
sm_kind = ContextKind
ctxt_kind })
                         [LHsTyVarBndr () GhcRn]
hs_bndrs TcM a
thing_inside
    -- sm_clone=False: see Note [Cloning for type variable binders]

bindExplicitTKBndrsX :: (OutputableBndrFlag flag 'Renamed)
    => SkolemMode
    -> [LHsTyVarBndr flag GhcRn]
    -> TcM a
    -> TcM ([VarBndr TyVar flag], a)  -- Returned [TcTyVar] are in 1-1 correspondence
                                      -- with the passed-in [LHsTyVarBndr]
bindExplicitTKBndrsX :: forall flag a.
OutputableBndrFlag flag 'Renamed =>
SkolemMode
-> [LHsTyVarBndr flag GhcRn]
-> TcM a
-> TcM ([VarBndr TyVar flag], a)
bindExplicitTKBndrsX skol_mode :: SkolemMode
skol_mode@(SM { sm_parent :: SkolemMode -> Bool
sm_parent = Bool
check_parent, sm_kind :: SkolemMode -> ContextKind
sm_kind = ContextKind
ctxt_kind
                                   , sm_holes :: SkolemMode -> HoleInfo
sm_holes = HoleInfo
hole_info })
                     [LHsTyVarBndr flag GhcRn]
hs_tvs TcM a
thing_inside
  = do { String -> SDoc -> TcM ()
traceTc String
"bindExplicitTKBndrs" ([GenLocated SrcSpanAnnA (HsTyVarBndr flag GhcRn)] -> SDoc
forall a. Outputable a => a -> SDoc
ppr [GenLocated SrcSpanAnnA (HsTyVarBndr flag GhcRn)]
[LHsTyVarBndr flag GhcRn]
hs_tvs)
       ; [GenLocated SrcSpanAnnA (HsTyVarBndr flag GhcRn)]
-> TcM ([VarBndr TyVar flag], a)
go [GenLocated SrcSpanAnnA (HsTyVarBndr flag GhcRn)]
[LHsTyVarBndr flag GhcRn]
hs_tvs }
  where
    tc_ki_mode :: TcTyMode
tc_ki_mode = TcTyMode { mode_tyki :: TypeOrKind
mode_tyki = TypeOrKind
KindLevel, mode_holes :: HoleInfo
mode_holes = HoleInfo
hole_info }
                 -- Inherit the HoleInfo from the context

    go :: [GenLocated SrcSpanAnnA (HsTyVarBndr flag GhcRn)]
-> TcM ([VarBndr TyVar flag], a)
go [] = do { a
res <- TcM a
thing_inside
               ; ([VarBndr TyVar flag], a) -> TcM ([VarBndr TyVar flag], a)
forall (m :: * -> *) a. Monad m => a -> m a
return ([], a
res) }
    go (L SrcSpanAnnA
_ HsTyVarBndr flag GhcRn
hs_tv : [GenLocated SrcSpanAnnA (HsTyVarBndr flag GhcRn)]
hs_tvs)
       = do { NameEnv TcTyThing
lcl_env <- TcM (NameEnv TcTyThing)
getLclTypeEnv
            ; TyVar
tv <- NameEnv TcTyThing
-> HsTyVarBndr flag GhcRn -> IOEnv (Env TcGblEnv TcLclEnv) TyVar
tc_hs_bndr NameEnv TcTyThing
lcl_env HsTyVarBndr flag GhcRn
hs_tv
            -- Extend the environment as we go, in case a binder
            -- is mentioned in the kind of a later binder
            --   e.g. forall k (a::k). blah
            -- NB: tv's Name may differ from hs_tv's
            -- See Note [Cloning for type variable binders]
            ; ([VarBndr TyVar flag]
tvs,a
res) <- [(Name, TyVar)]
-> TcM ([VarBndr TyVar flag], a) -> TcM ([VarBndr TyVar flag], a)
forall r. [(Name, TyVar)] -> TcM r -> TcM r
tcExtendNameTyVarEnv [(HsTyVarBndr flag GhcRn -> IdP GhcRn
forall flag (p :: Pass).
HsTyVarBndr flag (GhcPass p) -> IdP (GhcPass p)
hsTyVarName HsTyVarBndr flag GhcRn
hs_tv, TyVar
tv)] (TcM ([VarBndr TyVar flag], a) -> TcM ([VarBndr TyVar flag], a))
-> TcM ([VarBndr TyVar flag], a) -> TcM ([VarBndr TyVar flag], a)
forall a b. (a -> b) -> a -> b
$
                           [GenLocated SrcSpanAnnA (HsTyVarBndr flag GhcRn)]
-> TcM ([VarBndr TyVar flag], a)
go [GenLocated SrcSpanAnnA (HsTyVarBndr flag GhcRn)]
hs_tvs
            ; ([VarBndr TyVar flag], a) -> TcM ([VarBndr TyVar flag], a)
forall (m :: * -> *) a. Monad m => a -> m a
return (TyVar -> flag -> VarBndr TyVar flag
forall var argf. var -> argf -> VarBndr var argf
Bndr TyVar
tv (HsTyVarBndr flag GhcRn -> flag
forall flag (pass :: Pass). HsTyVarBndr flag (GhcPass pass) -> flag
hsTyVarBndrFlag HsTyVarBndr flag GhcRn
hs_tv)VarBndr TyVar flag -> [VarBndr TyVar flag] -> [VarBndr TyVar flag]
forall a. a -> [a] -> [a]
:[VarBndr TyVar flag]
tvs, a
res) }


    tc_hs_bndr :: NameEnv TcTyThing
-> HsTyVarBndr flag GhcRn -> IOEnv (Env TcGblEnv TcLclEnv) TyVar
tc_hs_bndr NameEnv TcTyThing
lcl_env (UserTyVar XUserTyVar GhcRn
_ flag
_ (L Anno (IdGhcP 'Renamed)
_ Name
name))
      | Bool
check_parent
      , Just (ATyVar Name
_ TyVar
tv) <- NameEnv TcTyThing -> Name -> Maybe TcTyThing
forall a. NameEnv a -> Name -> Maybe a
lookupNameEnv NameEnv TcTyThing
lcl_env Name
name
      = TyVar -> IOEnv (Env TcGblEnv TcLclEnv) TyVar
forall (m :: * -> *) a. Monad m => a -> m a
return TyVar
tv
      | Bool
otherwise
      = do { Type
kind <- ContextKind -> TcM Type
newExpectedKind ContextKind
ctxt_kind
           ; SkolemMode -> Name -> Type -> IOEnv (Env TcGblEnv TcLclEnv) TyVar
newTyVarBndr SkolemMode
skol_mode Name
name Type
kind }

    tc_hs_bndr NameEnv TcTyThing
lcl_env (KindedTyVar XKindedTyVar GhcRn
_ flag
_ (L Anno (IdGhcP 'Renamed)
_ Name
name) LHsType GhcRn
lhs_kind)
      | Bool
check_parent
      , Just (ATyVar Name
_ TyVar
tv) <- NameEnv TcTyThing -> Name -> Maybe TcTyThing
forall a. NameEnv a -> Name -> Maybe a
lookupNameEnv NameEnv TcTyThing
lcl_env Name
name
      = do { Type
kind <- TcTyMode -> UserTypeCtxt -> LHsType GhcRn -> TcM Type
tc_lhs_kind_sig TcTyMode
tc_ki_mode (Name -> UserTypeCtxt
TyVarBndrKindCtxt Name
name) LHsType GhcRn
lhs_kind
           ; TcM Coercion -> TcM ()
forall a. TcM a -> TcM ()
discardResult (TcM Coercion -> TcM ()) -> TcM Coercion -> TcM ()
forall a b. (a -> b) -> a -> b
$
             Maybe SDoc -> Type -> Type -> TcM Coercion
unifyKind (SDoc -> Maybe SDoc
forall a. a -> Maybe a
Just (Name -> SDoc
forall a. Outputable a => a -> SDoc
ppr Name
name)) Type
kind (TyVar -> Type
tyVarKind TyVar
tv)
                          -- This unify rejects:
                          --    class C (m :: * -> *) where
                          --      type F (m :: *) = ...
           ; TyVar -> IOEnv (Env TcGblEnv TcLclEnv) TyVar
forall (m :: * -> *) a. Monad m => a -> m a
return TyVar
tv }

      | Bool
otherwise
      = do { Type
kind <- TcTyMode -> UserTypeCtxt -> LHsType GhcRn -> TcM Type
tc_lhs_kind_sig TcTyMode
tc_ki_mode (Name -> UserTypeCtxt
TyVarBndrKindCtxt Name
name) LHsType GhcRn
lhs_kind
           ; SkolemMode -> Name -> Type -> IOEnv (Env TcGblEnv TcLclEnv) TyVar
newTyVarBndr SkolemMode
skol_mode Name
name Type
kind }

newTyVarBndr :: SkolemMode -> Name -> Kind -> TcM TcTyVar
newTyVarBndr :: SkolemMode -> Name -> Type -> IOEnv (Env TcGblEnv TcLclEnv) TyVar
newTyVarBndr (SM { sm_clone :: SkolemMode -> Bool
sm_clone = Bool
clone, sm_tvtv :: SkolemMode -> Bool
sm_tvtv = Bool
tvtv }) Name
name Type
kind
  = do { Name
name <- case Bool
clone of
              Bool
True -> do { Unique
uniq <- TcRnIf TcGblEnv TcLclEnv Unique
forall gbl lcl. TcRnIf gbl lcl Unique
newUnique
                         ; Name -> TcM Name
forall (m :: * -> *) a. Monad m => a -> m a
return (Name -> Unique -> Name
setNameUnique Name
name Unique
uniq) }
              Bool
False -> Name -> TcM Name
forall (m :: * -> *) a. Monad m => a -> m a
return Name
name
       ; TcTyVarDetails
details <- case Bool
tvtv of
                 Bool
True  -> MetaInfo -> TcM TcTyVarDetails
newMetaDetails MetaInfo
TyVarTv
                 Bool
False -> do { TcLevel
lvl <- TcM TcLevel
getTcLevel
                             ; TcTyVarDetails -> TcM TcTyVarDetails
forall (m :: * -> *) a. Monad m => a -> m a
return (TcLevel -> Bool -> TcTyVarDetails
SkolemTv TcLevel
lvl Bool
False) }
       ; TyVar -> IOEnv (Env TcGblEnv TcLclEnv) TyVar
forall (m :: * -> *) a. Monad m => a -> m a
return (Name -> Type -> TcTyVarDetails -> TyVar
mkTcTyVar Name
name Type
kind TcTyVarDetails
details) }

--------------------------------------
--    Implicit tyvar binders
--------------------------------------

tcImplicitTKBndrsX :: SkolemMode -> SkolemInfo
                   -> [Name]
                   -> TcM a
                   -> TcM ([TcTyVar], a)
-- The workhorse:
--    push level, capture constraints,
--    and emit an implication constraint with a ForAllSkol ic_info,
--    so that it is subject to a telescope test.
tcImplicitTKBndrsX :: forall a.
SkolemMode -> SkolemInfo -> HsQTvsRn -> TcM a -> TcM ([TyVar], a)
tcImplicitTKBndrsX SkolemMode
skol_mode SkolemInfo
skol_info HsQTvsRn
bndrs TcM a
thing_inside
  = do { (TcLevel
tclvl, WantedConstraints
wanted, ([TyVar]
skol_tvs, a
res))
             <- TcM ([TyVar], a) -> TcM (TcLevel, WantedConstraints, ([TyVar], a))
forall a. TcM a -> TcM (TcLevel, WantedConstraints, a)
pushLevelAndCaptureConstraints       (TcM ([TyVar], a)
 -> TcM (TcLevel, WantedConstraints, ([TyVar], a)))
-> TcM ([TyVar], a)
-> TcM (TcLevel, WantedConstraints, ([TyVar], a))
forall a b. (a -> b) -> a -> b
$
                SkolemMode -> HsQTvsRn -> TcM a -> TcM ([TyVar], a)
forall a. SkolemMode -> HsQTvsRn -> TcM a -> TcM ([TyVar], a)
bindImplicitTKBndrsX SkolemMode
skol_mode HsQTvsRn
bndrs (TcM a -> TcM ([TyVar], a)) -> TcM a -> TcM ([TyVar], a)
forall a b. (a -> b) -> a -> b
$
                TcM a
thing_inside

       ; SkolemInfo -> [TyVar] -> TcLevel -> WantedConstraints -> TcM ()
emitResidualTvConstraint SkolemInfo
skol_info [TyVar]
skol_tvs TcLevel
tclvl WantedConstraints
wanted

       ; ([TyVar], a) -> TcM ([TyVar], a)
forall (m :: * -> *) a. Monad m => a -> m a
return ([TyVar]
skol_tvs, a
res) }

------------------
bindImplicitTKBndrs_Skol, bindImplicitTKBndrs_Tv,
  bindImplicitTKBndrs_Q_Skol, bindImplicitTKBndrs_Q_Tv
  :: [Name] -> TcM a -> TcM ([TcTyVar], a)
bindImplicitTKBndrs_Skol :: forall a. HsQTvsRn -> TcM a -> TcM ([TyVar], a)
bindImplicitTKBndrs_Skol   = SkolemMode -> HsQTvsRn -> TcM a -> TcM ([TyVar], a)
forall a. SkolemMode -> HsQTvsRn -> TcM a -> TcM ([TyVar], a)
bindImplicitTKBndrsX (SkolemMode
smVanilla { sm_clone :: Bool
sm_clone = Bool
True })
bindImplicitTKBndrs_Tv :: forall a. HsQTvsRn -> TcM a -> TcM ([TyVar], a)
bindImplicitTKBndrs_Tv     = SkolemMode -> HsQTvsRn -> TcM a -> TcM ([TyVar], a)
forall a. SkolemMode -> HsQTvsRn -> TcM a -> TcM ([TyVar], a)
bindImplicitTKBndrsX (SkolemMode
smVanilla { sm_clone :: Bool
sm_clone = Bool
True, sm_tvtv :: Bool
sm_tvtv = Bool
True })
bindImplicitTKBndrs_Q_Skol :: forall a. HsQTvsRn -> TcM a -> TcM ([TyVar], a)
bindImplicitTKBndrs_Q_Skol = SkolemMode -> HsQTvsRn -> TcM a -> TcM ([TyVar], a)
forall a. SkolemMode -> HsQTvsRn -> TcM a -> TcM ([TyVar], a)
bindImplicitTKBndrsX (SkolemMode
smVanilla { sm_clone :: Bool
sm_clone = Bool
False, sm_parent :: Bool
sm_parent = Bool
True })
bindImplicitTKBndrs_Q_Tv :: forall a. HsQTvsRn -> TcM a -> TcM ([TyVar], a)
bindImplicitTKBndrs_Q_Tv   = SkolemMode -> HsQTvsRn -> TcM a -> TcM ([TyVar], a)
forall a. SkolemMode -> HsQTvsRn -> TcM a -> TcM ([TyVar], a)
bindImplicitTKBndrsX (SkolemMode
smVanilla { sm_clone :: Bool
sm_clone = Bool
False, sm_parent :: Bool
sm_parent = Bool
True, sm_tvtv :: Bool
sm_tvtv = Bool
True })

bindImplicitTKBndrsX
   :: SkolemMode
   -> [Name]
   -> TcM a
   -> TcM ([TcTyVar], a)   -- Returned [TcTyVar] are in 1-1 correspondence
                           -- with the passed in [Name]
bindImplicitTKBndrsX :: forall a. SkolemMode -> HsQTvsRn -> TcM a -> TcM ([TyVar], a)
bindImplicitTKBndrsX skol_mode :: SkolemMode
skol_mode@(SM { sm_parent :: SkolemMode -> Bool
sm_parent = Bool
check_parent, sm_kind :: SkolemMode -> ContextKind
sm_kind = ContextKind
ctxt_kind })
                     HsQTvsRn
tv_names TcM a
thing_inside
  = do { NameEnv TcTyThing
lcl_env <- TcM (NameEnv TcTyThing)
getLclTypeEnv
       ; [TyVar]
tkvs <- (Name -> IOEnv (Env TcGblEnv TcLclEnv) TyVar)
-> HsQTvsRn -> TcM [TyVar]
forall (t :: * -> *) (m :: * -> *) a b.
(Traversable t, Monad m) =>
(a -> m b) -> t a -> m (t b)
mapM (NameEnv TcTyThing -> Name -> IOEnv (Env TcGblEnv TcLclEnv) TyVar
new_tv NameEnv TcTyThing
lcl_env) HsQTvsRn
tv_names
       ; String -> SDoc -> TcM ()
traceTc String
"bindImplicitTKBndrsX" (HsQTvsRn -> SDoc
forall a. Outputable a => a -> SDoc
ppr HsQTvsRn
tv_names SDoc -> SDoc -> SDoc
$$ [TyVar] -> SDoc
forall a. Outputable a => a -> SDoc
ppr [TyVar]
tkvs)
       ; a
res <- [(Name, TyVar)] -> TcM a -> TcM a
forall r. [(Name, TyVar)] -> TcM r -> TcM r
tcExtendNameTyVarEnv (HsQTvsRn
tv_names HsQTvsRn -> [TyVar] -> [(Name, TyVar)]
forall a b. [a] -> [b] -> [(a, b)]
`zip` [TyVar]
tkvs)
                TcM a
thing_inside
       ; ([TyVar], a) -> TcM ([TyVar], a)
forall (m :: * -> *) a. Monad m => a -> m a
return ([TyVar]
tkvs, a
res) }
  where
    new_tv :: NameEnv TcTyThing -> Name -> IOEnv (Env TcGblEnv TcLclEnv) TyVar
new_tv NameEnv TcTyThing
lcl_env Name
name
      | Bool
check_parent
      , Just (ATyVar Name
_ TyVar
tv) <- NameEnv TcTyThing -> Name -> Maybe TcTyThing
forall a. NameEnv a -> Name -> Maybe a
lookupNameEnv NameEnv TcTyThing
lcl_env Name
name
      = TyVar -> IOEnv (Env TcGblEnv TcLclEnv) TyVar
forall (m :: * -> *) a. Monad m => a -> m a
return TyVar
tv
      | Bool
otherwise
      = do { Type
kind <- ContextKind -> TcM Type
newExpectedKind ContextKind
ctxt_kind
           ; SkolemMode -> Name -> Type -> IOEnv (Env TcGblEnv TcLclEnv) TyVar
newTyVarBndr SkolemMode
skol_mode Name
name Type
kind }

--------------------------------------
--           SkolemMode
--------------------------------------

-- | 'SkolemMode' describes how to typecheck an explicit ('HsTyVarBndr') or
-- implicit ('Name') binder in a type. It is just a record of flags
-- that describe what sort of 'TcTyVar' to create.
data SkolemMode
  = SM { SkolemMode -> Bool
sm_parent :: Bool    -- True <=> check the in-scope parent type variable
                              -- Used only for asssociated types

       , SkolemMode -> Bool
sm_clone  :: Bool    -- True <=> fresh unique
                              -- See Note [Cloning for type variable binders]

       , SkolemMode -> Bool
sm_tvtv   :: Bool    -- True <=> use a TyVarTv, rather than SkolemTv
                              -- Why?  See Note [Inferring kinds for type declarations]
                              -- in GHC.Tc.TyCl, and (in this module)
                              -- Note [Checking partial type signatures]

       , SkolemMode -> ContextKind
sm_kind   :: ContextKind  -- Use this for the kind of any new binders

       , SkolemMode -> HoleInfo
sm_holes  :: HoleInfo     -- What to do for wildcards in the kind
       }

smVanilla :: SkolemMode
smVanilla :: SkolemMode
smVanilla = SM { sm_clone :: Bool
sm_clone  = String -> Bool
forall a. String -> a
panic String
"sm_clone"  -- We always override this
               , sm_parent :: Bool
sm_parent = Bool
False
               , sm_tvtv :: Bool
sm_tvtv   = Bool
False
               , sm_kind :: ContextKind
sm_kind   = ContextKind
AnyKind
               , sm_holes :: HoleInfo
sm_holes  = HoleInfo
forall a. Maybe a
Nothing }

{- Note [Cloning for type variable binders]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Sometimes we must clone the Name of a type variable binder (written in
the source program); and sometimes we must not. This is controlled by
the sm_clone field of SkolemMode.

In some cases it doesn't matter whether or not we clone. Perhaps
it'd be better to use MustClone/MayClone/MustNotClone.

When we /must not/ clone
* In the binders of a type signature (tcOuterTKBndrs)
      f :: forall a{27}. blah
      f = rhs
  Then 'a' scopes over 'rhs'. When we kind-check the signature (tcHsSigType),
  we must get the type (forall a{27}. blah) for the Id f, because
  we bring that type variable into scope when we typecheck 'rhs'.

* In the binders of a data family instance (bindOuterFamEqnTKBndrs)
     data instance
       forall p q. D (p,q) = D1 p | D2 q
  We kind-check the LHS in tcDataFamInstHeader, and then separately
  (in tcDataFamInstDecl) bring p,q into scope before looking at the
  the constructor decls.

* bindExplicitTKBndrs_Q_Tv/bindImplicitTKBndrs_Q_Tv do not clone
  We take advantage of this in kcInferDeclHeader:
     all_tv_prs = mkTyVarNamePairs (scoped_kvs ++ tc_tvs)
  If we cloned, we'd need to take a bit more care here; not hard.

* bindExplicitTKBndrs_Q_Skol, bindExplicitTKBndrs_Skol, do not clone.
  There is no need, I think.

  The payoff here is that avoiding gratuitous cloning means that we can
  almost always take the fast path in swizzleTcTyConBndrs.

When we /must/ clone.
* bindOuterSigTKBndrs_Tv, bindExplicitTKBndrs_Tv do cloning

  This for a narrow and tricky reason which, alas, I couldn't find a
  simpler way round.  #16221 is the poster child:

     data SameKind :: k -> k -> *
     data T a = forall k2 (b :: k2). MkT (SameKind a b) !Int

  When kind-checking T, we give (a :: kappa1). Then:

  - In kcConDecl we make a TyVarTv unification variable kappa2 for k2
    (as described in Note [Using TyVarTvs for kind-checking GADTs],
    even though this example is an existential)
  - So we get (b :: kappa2) via bindExplicitTKBndrs_Tv
  - We end up unifying kappa1 := kappa2, because of the (SameKind a b)

  Now we generalise over kappa2. But if kappa2's Name is precisely k2
  (i.e. we did not clone) we'll end up giving T the utterly final kind
    T :: forall k2. k2 -> *
  Nothing directly wrong with that but when we typecheck the data constructor
  we have k2 in scope; but then it's brought into scope /again/ when we find
  the forall k2.  This is chaotic, and we end up giving it the type
    MkT :: forall k2 (a :: k2) k2 (b :: k2).
           SameKind @k2 a b -> Int -> T @{k2} a
  which is bogus -- because of the shadowing of k2, we can't
  apply T to the kind or a!

  And there no reason /not/ to clone the Name when making a unification
  variable.  So that's what we do.
-}

--------------------------------------
-- Binding type/class variables in the
-- kind-checking and typechecking phases
--------------------------------------

bindTyClTyVars :: Name
               -> (TcTyCon -> [TyConBinder] -> Kind -> TcM a) -> TcM a
-- ^ Used for the type variables of a type or class decl
-- in the "kind checking" and "type checking" pass,
-- but not in the initial-kind run.
bindTyClTyVars :: forall a.
Name -> (TyCon -> [TyConBinder] -> Type -> TcM a) -> TcM a
bindTyClTyVars Name
tycon_name TyCon -> [TyConBinder] -> Type -> TcM a
thing_inside
  = do { TyCon
tycon <- HasDebugCallStack => Name -> TcM TyCon
Name -> TcM TyCon
tcLookupTcTyCon Name
tycon_name
       ; let scoped_prs :: [(Name, TyVar)]
scoped_prs = TyCon -> [(Name, TyVar)]
tcTyConScopedTyVars TyCon
tycon
             res_kind :: Type
res_kind   = TyCon -> Type
tyConResKind TyCon
tycon
             binders :: [TyConBinder]
binders    = TyCon -> [TyConBinder]
tyConBinders TyCon
tycon
       ; String -> SDoc -> TcM ()
traceTc String
"bindTyClTyVars" (Name -> SDoc
forall a. Outputable a => a -> SDoc
ppr Name
tycon_name SDoc -> SDoc -> SDoc
<+> [TyConBinder] -> SDoc
forall a. Outputable a => a -> SDoc
ppr [TyConBinder]
binders SDoc -> SDoc -> SDoc
$$ [(Name, TyVar)] -> SDoc
forall a. Outputable a => a -> SDoc
ppr [(Name, TyVar)]
scoped_prs)
       ; [(Name, TyVar)] -> TcM a -> TcM a
forall r. [(Name, TyVar)] -> TcM r -> TcM r
tcExtendNameTyVarEnv [(Name, TyVar)]
scoped_prs (TcM a -> TcM a) -> TcM a -> TcM a
forall a b. (a -> b) -> a -> b
$
         TyCon -> [TyConBinder] -> Type -> TcM a
thing_inside TyCon
tycon [TyConBinder]
binders Type
res_kind }


{- *********************************************************************
*                                                                      *
             Kind generalisation
*                                                                      *
********************************************************************* -}

zonkAndScopedSort :: [TcTyVar] -> TcM [TcTyVar]
zonkAndScopedSort :: [TyVar] -> TcM [TyVar]
zonkAndScopedSort [TyVar]
spec_tkvs
  = do { [TyVar]
spec_tkvs <- (TyVar -> IOEnv (Env TcGblEnv TcLclEnv) TyVar)
-> [TyVar] -> TcM [TyVar]
forall (t :: * -> *) (m :: * -> *) a b.
(Traversable t, Monad m) =>
(a -> m b) -> t a -> m (t b)
mapM HasDebugCallStack => TyVar -> IOEnv (Env TcGblEnv TcLclEnv) TyVar
TyVar -> IOEnv (Env TcGblEnv TcLclEnv) TyVar
zonkTcTyVarToTyVar [TyVar]
spec_tkvs
         -- Zonk the kinds, to we can do the dependency analayis

       -- Do a stable topological sort, following
       -- Note [Ordering of implicit variables] in GHC.Rename.HsType
       ; [TyVar] -> TcM [TyVar]
forall (m :: * -> *) a. Monad m => a -> m a
return ([TyVar] -> [TyVar]
scopedSort [TyVar]
spec_tkvs) }

-- | Generalize some of the free variables in the given type.
-- All such variables should be *kind* variables; any type variables
-- should be explicitly quantified (with a `forall`) before now.
--
-- The WantedConstraints are un-solved kind constraints. Generally
-- they'll be reported as errors later, but meanwhile we refrain
-- from quantifying over any variable free in these unsolved
-- constraints. See Note [Failure in local type signatures].
--
-- But in all cases, generalize only those variables whose TcLevel is
-- strictly greater than the ambient level. This "strictly greater
-- than" means that you likely need to push the level before creating
-- whatever type gets passed here.
--
-- Any variable whose level is greater than the ambient level but is
-- not selected to be generalized will be promoted. (See [Promoting
-- unification variables] in "GHC.Tc.Solver" and Note [Recipe for
-- checking a signature].)
--
-- The resulting KindVar are the variables to quantify over, in the
-- correct, well-scoped order. They should generally be Inferred, not
-- Specified, but that's really up to the caller of this function.
kindGeneralizeSome :: WantedConstraints
                   -> TcType    -- ^ needn't be zonked
                   -> TcM [KindVar]
kindGeneralizeSome :: WantedConstraints -> Type -> TcM [TyVar]
kindGeneralizeSome WantedConstraints
wanted Type
kind_or_type
  = do { -- Use the "Kind" variant here, as any types we see
         -- here will already have all type variables quantified;
         -- thus, every free variable is really a kv, never a tv.
       ; CandidatesQTvs
dvs <- Type -> TcM CandidatesQTvs
candidateQTyVarsOfKind Type
kind_or_type
       ; CandidatesQTvs
dvs <- WantedConstraints -> CandidatesQTvs -> TcM CandidatesQTvs
filterConstrainedCandidates WantedConstraints
wanted CandidatesQTvs
dvs
       ; CandidatesQTvs -> TcM [TyVar]
quantifyTyVars CandidatesQTvs
dvs }

filterConstrainedCandidates
  :: WantedConstraints    -- Don't quantify over variables free in these
                          --   Not necessarily fully zonked
  -> CandidatesQTvs       -- Candidates for quantification
  -> TcM CandidatesQTvs
-- filterConstrainedCandidates removes any candidates that are free in
-- 'wanted'; instead, it promotes them.  This bit is very much like
-- decideMonoTyVars in GHC.Tc.Solver, but constraints are so much
-- simpler in kinds, it is much easier here. (In particular, we never
-- quantify over a constraint in a type.)
filterConstrainedCandidates :: WantedConstraints -> CandidatesQTvs -> TcM CandidatesQTvs
filterConstrainedCandidates WantedConstraints
wanted CandidatesQTvs
dvs
  | WantedConstraints -> Bool
isEmptyWC WantedConstraints
wanted   -- Fast path for a common case
  = CandidatesQTvs -> TcM CandidatesQTvs
forall (m :: * -> *) a. Monad m => a -> m a
return CandidatesQTvs
dvs
  | Bool
otherwise
  = do { VarSet
wc_tvs <- VarSet -> TcM VarSet
zonkTyCoVarsAndFV (WantedConstraints -> VarSet
tyCoVarsOfWC WantedConstraints
wanted)
       ; let (VarSet
to_promote, CandidatesQTvs
dvs') = CandidatesQTvs -> (TyVar -> Bool) -> (VarSet, CandidatesQTvs)
partitionCandidates CandidatesQTvs
dvs (TyVar -> VarSet -> Bool
`elemVarSet` VarSet
wc_tvs)
       ; Bool
_ <- VarSet -> TcRnIf TcGblEnv TcLclEnv Bool
promoteTyVarSet VarSet
to_promote
       ; CandidatesQTvs -> TcM CandidatesQTvs
forall (m :: * -> *) a. Monad m => a -> m a
return CandidatesQTvs
dvs' }

-- |- Specialised version of 'kindGeneralizeSome', but with empty
-- WantedConstraints, so no filtering is needed
-- i.e.   kindGeneraliseAll = kindGeneralizeSome emptyWC
kindGeneralizeAll :: TcType -> TcM [KindVar]
kindGeneralizeAll :: Type -> TcM [TyVar]
kindGeneralizeAll Type
kind_or_type
  = do { String -> SDoc -> TcM ()
traceTc String
"kindGeneralizeAll" (Type -> SDoc
forall a. Outputable a => a -> SDoc
ppr Type
kind_or_type)
       ; CandidatesQTvs
dvs <- Type -> TcM CandidatesQTvs
candidateQTyVarsOfKind Type
kind_or_type
       ; CandidatesQTvs -> TcM [TyVar]
quantifyTyVars CandidatesQTvs
dvs }

-- | Specialized version of 'kindGeneralizeSome', but where no variables
-- can be generalized, but perhaps some may need to be promoted.
-- Use this variant when it is unknowable whether metavariables might
-- later be constrained.
--
-- To see why this promotion is needed, see
-- Note [Recipe for checking a signature], and especially
-- Note [Promotion in signatures].
kindGeneralizeNone :: TcType  -- needn't be zonked
                   -> TcM ()
kindGeneralizeNone :: Type -> TcM ()
kindGeneralizeNone Type
kind_or_type
  = do { String -> SDoc -> TcM ()
traceTc String
"kindGeneralizeNone" (Type -> SDoc
forall a. Outputable a => a -> SDoc
ppr Type
kind_or_type)
       ; CandidatesQTvs
dvs <- Type -> TcM CandidatesQTvs
candidateQTyVarsOfKind Type
kind_or_type
       ; Bool
_ <- VarSet -> TcRnIf TcGblEnv TcLclEnv Bool
promoteTyVarSet (CandidatesQTvs -> VarSet
candidateKindVars CandidatesQTvs
dvs)
       ; () -> TcM ()
forall (m :: * -> *) a. Monad m => a -> m a
return () }

{- Note [Levels and generalisation]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Consider
  f x = e
with no type signature. We are currently at level i.
We must
  * Push the level to level (i+1)
  * Allocate a fresh alpha[i+1] for the result type
  * Check that e :: alpha[i+1], gathering constraint WC
  * Solve WC as far as possible
  * Zonking the result type alpha[i+1], say to beta[i-1] -> gamma[i]
  * Find the free variables with level > i, in this case gamma[i]
  * Skolemise those free variables and quantify over them, giving
       f :: forall g. beta[i-1] -> g
  * Emit the residiual constraint wrapped in an implication for g,
    thus   forall g. WC

All of this happens for types too.  Consider
  f :: Int -> (forall a. Proxy a -> Int)

Note [Kind generalisation]
~~~~~~~~~~~~~~~~~~~~~~~~~~
We do kind generalisation only at the outer level of a type signature.
For example, consider
  T :: forall k. k -> *
  f :: (forall a. T a -> Int) -> Int
When kind-checking f's type signature we generalise the kind at
the outermost level, thus:
  f1 :: forall k. (forall (a:k). T k a -> Int) -> Int  -- YES!
and *not* at the inner forall:
  f2 :: (forall k. forall (a:k). T k a -> Int) -> Int  -- NO!
Reason: same as for HM inference on value level declarations,
we want to infer the most general type.  The f2 type signature
would be *less applicable* than f1, because it requires a more
polymorphic argument.

NB: There are no explicit kind variables written in f's signature.
When there are, the renamer adds these kind variables to the list of
variables bound by the forall, so you can indeed have a type that's
higher-rank in its kind. But only by explicit request.

Note [Kinds of quantified type variables]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
tcTyVarBndrsGen quantifies over a specified list of type variables,
*and* over the kind variables mentioned in the kinds of those tyvars.

Note that we must zonk those kinds (obviously) but less obviously, we
must return type variables whose kinds are zonked too. Example
    (a :: k7)  where  k7 := k9 -> k9
We must return
    [k9, a:k9->k9]
and NOT
    [k9, a:k7]
Reason: we're going to turn this into a for-all type,
   forall k9. forall (a:k7). blah
which the type checker will then instantiate, and instantiate does not
look through unification variables!

Hence using zonked_kinds when forming tvs'.

-}

-----------------------------------
etaExpandAlgTyCon :: [TyConBinder]
                  -> Kind   -- must be zonked
                  -> TcM ([TyConBinder], Kind)
-- GADT decls can have a (perhaps partial) kind signature
--      e.g.  data T a :: * -> * -> * where ...
-- This function makes up suitable (kinded) TyConBinders for the
-- argument kinds.  E.g. in this case it might return
--   ([b::*, c::*], *)
-- Never emits constraints.
-- It's a little trickier than you might think: see
-- Note [TyConBinders for the result kind signature of a data type]
-- See Note [Datatype return kinds] in GHC.Tc.TyCl
etaExpandAlgTyCon :: [TyConBinder] -> Type -> TcM ([TyConBinder], Type)
etaExpandAlgTyCon [TyConBinder]
tc_bndrs Type
kind
  = do  { SrcSpan
loc     <- TcRn SrcSpan
getSrcSpanM
        ; UniqSupply
uniqs   <- TcRnIf TcGblEnv TcLclEnv UniqSupply
forall gbl lcl. TcRnIf gbl lcl UniqSupply
newUniqueSupply
        ; LocalRdrEnv
rdr_env <- RnM LocalRdrEnv
getLocalRdrEnv
        ; let new_occs :: [OccName]
new_occs = [ OccName
occ
                         | String
str <- [String]
allNameStrings
                         , let occ :: OccName
occ = NameSpace -> String -> OccName
mkOccName NameSpace
tvName String
str
                         , Maybe Name -> Bool
forall a. Maybe a -> Bool
isNothing (LocalRdrEnv -> OccName -> Maybe Name
lookupLocalRdrOcc LocalRdrEnv
rdr_env OccName
occ)
                         -- Note [Avoid name clashes for associated data types]
                         , Bool -> Bool
not (OccName
occ OccName -> [OccName] -> Bool
forall (t :: * -> *) a. (Foldable t, Eq a) => a -> t a -> Bool
`elem` [OccName]
lhs_occs) ]
              new_uniqs :: [Unique]
new_uniqs = UniqSupply -> [Unique]
uniqsFromSupply UniqSupply
uniqs
              subst :: TCvSubst
subst = InScopeSet -> TCvSubst
mkEmptyTCvSubst (VarSet -> InScopeSet
mkInScopeSet ([TyVar] -> VarSet
mkVarSet [TyVar]
lhs_tvs))
        ; ([TyConBinder], Type) -> TcM ([TyConBinder], Type)
forall (m :: * -> *) a. Monad m => a -> m a
return (SrcSpan
-> [OccName]
-> [Unique]
-> TCvSubst
-> [TyConBinder]
-> Type
-> ([TyConBinder], Type)
go SrcSpan
loc [OccName]
new_occs [Unique]
new_uniqs TCvSubst
subst [] Type
kind) }
  where
    lhs_tvs :: [TyVar]
lhs_tvs  = (TyConBinder -> TyVar) -> [TyConBinder] -> [TyVar]
forall a b. (a -> b) -> [a] -> [b]
map TyConBinder -> TyVar
forall tv argf. VarBndr tv argf -> tv
binderVar [TyConBinder]
tc_bndrs
    lhs_occs :: [OccName]
lhs_occs = (TyVar -> OccName) -> [TyVar] -> [OccName]
forall a b. (a -> b) -> [a] -> [b]
map TyVar -> OccName
forall a. NamedThing a => a -> OccName
getOccName [TyVar]
lhs_tvs

    go :: SrcSpan
-> [OccName]
-> [Unique]
-> TCvSubst
-> [TyConBinder]
-> Type
-> ([TyConBinder], Type)
go SrcSpan
loc [OccName]
occs [Unique]
uniqs TCvSubst
subst [TyConBinder]
acc Type
kind
      = case Type -> Maybe (TyBinder, Type)
splitPiTy_maybe Type
kind of
          Maybe (TyBinder, Type)
Nothing -> ([TyConBinder] -> [TyConBinder]
forall a. [a] -> [a]
reverse [TyConBinder]
acc, HasCallStack => TCvSubst -> Type -> Type
TCvSubst -> Type -> Type
substTy TCvSubst
subst Type
kind)

          Just (Anon AnonArgFlag
af Scaled Type
arg, Type
kind')
            -> SrcSpan
-> [OccName]
-> [Unique]
-> TCvSubst
-> [TyConBinder]
-> Type
-> ([TyConBinder], Type)
go SrcSpan
loc [OccName]
occs' [Unique]
uniqs' TCvSubst
subst' (TyConBinder
tcb TyConBinder -> [TyConBinder] -> [TyConBinder]
forall a. a -> [a] -> [a]
: [TyConBinder]
acc) Type
kind'
            where
              arg' :: Type
arg'   = HasCallStack => TCvSubst -> Type -> Type
TCvSubst -> Type -> Type
substTy TCvSubst
subst (Scaled Type -> Type
forall a. Scaled a -> a
scaledThing Scaled Type
arg)
              tv :: TyVar
tv     = Name -> Type -> TyVar
mkTyVar (Unique -> OccName -> SrcSpan -> Name
mkInternalName Unique
uniq OccName
occ SrcSpan
loc) Type
arg'
              subst' :: TCvSubst
subst' = TCvSubst -> TyVar -> TCvSubst
extendTCvInScope TCvSubst
subst TyVar
tv
              tcb :: TyConBinder
tcb    = TyVar -> TyConBndrVis -> TyConBinder
forall var argf. var -> argf -> VarBndr var argf
Bndr TyVar
tv (AnonArgFlag -> TyConBndrVis
AnonTCB AnonArgFlag
af)
              (Unique
uniq:[Unique]
uniqs') = [Unique]
uniqs
              (OccName
occ:[OccName]
occs')   = [OccName]
occs

          Just (Named (Bndr TyVar
tv ArgFlag
vis), Type
kind')
            -> SrcSpan
-> [OccName]
-> [Unique]
-> TCvSubst
-> [TyConBinder]
-> Type
-> ([TyConBinder], Type)
go SrcSpan
loc [OccName]
occs [Unique]
uniqs TCvSubst
subst' (TyConBinder
tcb TyConBinder -> [TyConBinder] -> [TyConBinder]
forall a. a -> [a] -> [a]
: [TyConBinder]
acc) Type
kind'
            where
              (TCvSubst
subst', TyVar
tv') = HasCallStack => TCvSubst -> TyVar -> (TCvSubst, TyVar)
TCvSubst -> TyVar -> (TCvSubst, TyVar)
substTyVarBndr TCvSubst
subst TyVar
tv
              tcb :: TyConBinder
tcb = TyVar -> TyConBndrVis -> TyConBinder
forall var argf. var -> argf -> VarBndr var argf
Bndr TyVar
tv' (ArgFlag -> TyConBndrVis
NamedTCB ArgFlag
vis)

-- | A description of whether something is a
--
-- * @data@ or @newtype@ ('DataDeclSort')
--
-- * @data instance@ or @newtype instance@ ('DataInstanceSort')
--
-- * @data family@ ('DataFamilySort')
--
-- At present, this data type is only consumed by 'checkDataKindSig'.
data DataSort
  = DataDeclSort     NewOrData
  | DataInstanceSort NewOrData
  | DataFamilySort

-- | Local helper type used in 'checkDataKindSig'.
--
-- Superficially similar to 'ContextKind', but it lacks 'AnyKind'
-- and 'AnyBoxedKind', and instead of @'TheKind' liftedTypeKind@
-- provides 'LiftedKind', which is much simpler to match on and
-- handle in 'isAllowedDataResKind'.
data AllowedDataResKind
  = AnyTYPEKind
  | AnyBoxedKind
  | LiftedKind

isAllowedDataResKind :: AllowedDataResKind -> Kind -> Bool
isAllowedDataResKind :: AllowedDataResKind -> Type -> Bool
isAllowedDataResKind AllowedDataResKind
AnyTYPEKind  Type
kind = Type -> Bool
tcIsRuntimeTypeKind Type
kind
isAllowedDataResKind AllowedDataResKind
AnyBoxedKind Type
kind = Type -> Bool
tcIsBoxedTypeKind Type
kind
isAllowedDataResKind AllowedDataResKind
LiftedKind   Type
kind = Type -> Bool
tcIsLiftedTypeKind Type
kind

-- | Checks that the return kind in a data declaration's kind signature is
-- permissible. There are three cases:
--
-- If dealing with a @data@, @newtype@, @data instance@, or @newtype instance@
-- declaration, check that the return kind is @Type@.
--
-- If the declaration is a @newtype@ or @newtype instance@ and the
-- @UnliftedNewtypes@ extension is enabled, this check is slightly relaxed so
-- that a return kind of the form @TYPE r@ (for some @r@) is permitted.
-- See @Note [Implementation of UnliftedNewtypes]@ in "GHC.Tc.TyCl".
--
-- If dealing with a @data family@ declaration, check that the return kind is
-- either of the form:
--
-- 1. @TYPE r@ (for some @r@), or
--
-- 2. @k@ (where @k@ is a bare kind variable; see #12369)
--
-- See also Note [Datatype return kinds] in "GHC.Tc.TyCl"
checkDataKindSig :: DataSort -> Kind  -- any arguments in the kind are stripped off
                 -> TcM ()
checkDataKindSig :: DataSort -> Type -> TcM ()
checkDataKindSig DataSort
data_sort Type
kind
  = do { DynFlags
dflags <- IOEnv (Env TcGblEnv TcLclEnv) DynFlags
forall (m :: * -> *). HasDynFlags m => m DynFlags
getDynFlags
       ; String -> SDoc -> TcM ()
traceTc String
"checkDataKindSig" (Type -> SDoc
forall a. Outputable a => a -> SDoc
ppr Type
kind)
       ; Bool -> SDoc -> TcM ()
checkTc (DynFlags -> Bool
tYPE_ok DynFlags
dflags Bool -> Bool -> Bool
|| Bool
is_kind_var)
                 (DynFlags -> SDoc
err_msg DynFlags
dflags) }
  where
    res_kind :: Type
res_kind = ([TyBinder], Type) -> Type
forall a b. (a, b) -> b
snd (Type -> ([TyBinder], Type)
tcSplitPiTys Type
kind)
       -- Look for the result kind after
       -- peeling off any foralls and arrows

    pp_dec :: SDoc
    pp_dec :: SDoc
pp_dec = String -> SDoc
text (String -> SDoc) -> String -> SDoc
forall a b. (a -> b) -> a -> b
$
      case DataSort
data_sort of
        DataDeclSort     NewOrData
DataType -> String
"Data type"
        DataDeclSort     NewOrData
NewType  -> String
"Newtype"
        DataInstanceSort NewOrData
DataType -> String
"Data instance"
        DataInstanceSort NewOrData
NewType  -> String
"Newtype instance"
        DataSort
DataFamilySort            -> String
"Data family"

    is_newtype :: Bool
    is_newtype :: Bool
is_newtype =
      case DataSort
data_sort of
        DataDeclSort     NewOrData
new_or_data -> NewOrData
new_or_data NewOrData -> NewOrData -> Bool
forall a. Eq a => a -> a -> Bool
== NewOrData
NewType
        DataInstanceSort NewOrData
new_or_data -> NewOrData
new_or_data NewOrData -> NewOrData -> Bool
forall a. Eq a => a -> a -> Bool
== NewOrData
NewType
        DataSort
DataFamilySort               -> Bool
False

    is_datatype :: Bool
    is_datatype :: Bool
is_datatype =
      case DataSort
data_sort of
        DataDeclSort     NewOrData
DataType -> Bool
True
        DataInstanceSort NewOrData
DataType -> Bool
True
        DataSort
_                         -> Bool
False

    is_data_family :: Bool
    is_data_family :: Bool
is_data_family =
      case DataSort
data_sort of
        DataDeclSort{}     -> Bool
False
        DataInstanceSort{} -> Bool
False
        DataSort
DataFamilySort     -> Bool
True

    allowed_kind :: DynFlags -> AllowedDataResKind
    allowed_kind :: DynFlags -> AllowedDataResKind
allowed_kind DynFlags
dflags
      | Bool
is_newtype Bool -> Bool -> Bool
&& Extension -> DynFlags -> Bool
xopt Extension
LangExt.UnliftedNewtypes DynFlags
dflags
        -- With UnliftedNewtypes, we allow kinds other than Type, but they
        -- must still be of the form `TYPE r` since we don't want to accept
        -- Constraint or Nat.
        -- See Note [Implementation of UnliftedNewtypes] in GHC.Tc.TyCl.
      = AllowedDataResKind
AnyTYPEKind
      | Bool
is_data_family
        -- If this is a `data family` declaration, we don't need to check if
        -- UnliftedNewtypes is enabled, since data family declarations can
        -- have return kind `TYPE r` unconditionally (#16827).
      = AllowedDataResKind
AnyTYPEKind
      | Bool
is_datatype Bool -> Bool -> Bool
&& Extension -> DynFlags -> Bool
xopt Extension
LangExt.UnliftedDatatypes DynFlags
dflags
        -- With UnliftedDatatypes, we allow kinds other than Type, but they
        -- must still be of the form `TYPE (BoxedRep l)`, so that we don't
        -- accept result kinds like `TYPE IntRep`.
        -- See Note [Implementation of UnliftedDatatypes] in GHC.Tc.TyCl.
      = AllowedDataResKind
AnyBoxedKind
      | Bool
otherwise
      = AllowedDataResKind
LiftedKind

    tYPE_ok :: DynFlags -> Bool
    tYPE_ok :: DynFlags -> Bool
tYPE_ok DynFlags
dflags = AllowedDataResKind -> Type -> Bool
isAllowedDataResKind (DynFlags -> AllowedDataResKind
allowed_kind DynFlags
dflags) Type
res_kind

    -- In the particular case of a data family, permit a return kind of the
    -- form `:: k` (where `k` is a bare kind variable).
    is_kind_var :: Bool
    is_kind_var :: Bool
is_kind_var | Bool
is_data_family = Maybe (TyVar, Coercion) -> Bool
forall a. Maybe a -> Bool
isJust (Type -> Maybe (TyVar, Coercion)
tcGetCastedTyVar_maybe Type
res_kind)
                | Bool
otherwise      = Bool
False

    pp_allowed_kind :: DynFlags -> SDoc
pp_allowed_kind DynFlags
dflags =
      case DynFlags -> AllowedDataResKind
allowed_kind DynFlags
dflags of
        AllowedDataResKind
AnyTYPEKind  -> TyCon -> SDoc
forall a. Outputable a => a -> SDoc
ppr TyCon
tYPETyCon
        AllowedDataResKind
AnyBoxedKind -> TyCon -> SDoc
forall a. Outputable a => a -> SDoc
ppr TyCon
boxedRepDataConTyCon
        AllowedDataResKind
LiftedKind   -> Type -> SDoc
forall a. Outputable a => a -> SDoc
ppr Type
liftedTypeKind

    err_msg :: DynFlags -> SDoc
    err_msg :: DynFlags -> SDoc
err_msg DynFlags
dflags =
      [SDoc] -> SDoc
sep [ [SDoc] -> SDoc
sep [ SDoc
pp_dec SDoc -> SDoc -> SDoc
<+>
                  String -> SDoc
text String
"has non-" SDoc -> SDoc -> SDoc
<>
                  DynFlags -> SDoc
pp_allowed_kind DynFlags
dflags
                , (if Bool
is_data_family then String -> SDoc
text String
"and non-variable" else SDoc
empty) SDoc -> SDoc -> SDoc
<+>
                  String -> SDoc
text String
"return kind" SDoc -> SDoc -> SDoc
<+> SDoc -> SDoc
quotes (Type -> SDoc
forall a. Outputable a => a -> SDoc
ppr Type
kind) ]
          , DynFlags -> SDoc
ext_hint DynFlags
dflags ]

    ext_hint :: DynFlags -> SDoc
ext_hint DynFlags
dflags
      | Type -> Bool
tcIsRuntimeTypeKind Type
kind
      , Bool
is_newtype
      , Bool -> Bool
not (Extension -> DynFlags -> Bool
xopt Extension
LangExt.UnliftedNewtypes DynFlags
dflags)
      = String -> SDoc
text String
"Perhaps you intended to use UnliftedNewtypes"
      | Type -> Bool
tcIsBoxedTypeKind Type
kind
      , Bool
is_datatype
      , Bool -> Bool
not (Extension -> DynFlags -> Bool
xopt Extension
LangExt.UnliftedDatatypes DynFlags
dflags)
      = String -> SDoc
text String
"Perhaps you intended to use UnliftedDatatypes"
      | Bool
otherwise
      = SDoc
empty

-- | Checks that the result kind of a class is exactly `Constraint`, rejecting
-- type synonyms and type families that reduce to `Constraint`. See #16826.
checkClassKindSig :: Kind -> TcM ()
checkClassKindSig :: Type -> TcM ()
checkClassKindSig Type
kind = Bool -> SDoc -> TcM ()
checkTc (Type -> Bool
tcIsConstraintKind Type
kind) SDoc
err_msg
  where
    err_msg :: SDoc
    err_msg :: SDoc
err_msg =
      String -> SDoc
text String
"Kind signature on a class must end with" SDoc -> SDoc -> SDoc
<+> Type -> SDoc
forall a. Outputable a => a -> SDoc
ppr Type
constraintKind SDoc -> SDoc -> SDoc
$$
      String -> SDoc
text String
"unobscured by type families"

tcbVisibilities :: TyCon -> [Type] -> [TyConBndrVis]
-- Result is in 1-1 correspondence with orig_args
tcbVisibilities :: TyCon -> [Type] -> [TyConBndrVis]
tcbVisibilities TyCon
tc [Type]
orig_args
  = Type -> TCvSubst -> [Type] -> [TyConBndrVis]
go (TyCon -> Type
tyConKind TyCon
tc) TCvSubst
init_subst [Type]
orig_args
  where
    init_subst :: TCvSubst
init_subst = InScopeSet -> TCvSubst
mkEmptyTCvSubst (VarSet -> InScopeSet
mkInScopeSet ([Type] -> VarSet
tyCoVarsOfTypes [Type]
orig_args))
    go :: Type -> TCvSubst -> [Type] -> [TyConBndrVis]
go Type
_ TCvSubst
_ []
      = []

    go Type
fun_kind TCvSubst
subst all_args :: [Type]
all_args@(Type
arg : [Type]
args)
      | Just (TyBinder
tcb, Type
inner_kind) <- Type -> Maybe (TyBinder, Type)
splitPiTy_maybe Type
fun_kind
      = case TyBinder
tcb of
          Anon AnonArgFlag
af Scaled Type
_           -> AnonArgFlag -> TyConBndrVis
AnonTCB AnonArgFlag
af   TyConBndrVis -> [TyConBndrVis] -> [TyConBndrVis]
forall a. a -> [a] -> [a]
: Type -> TCvSubst -> [Type] -> [TyConBndrVis]
go Type
inner_kind TCvSubst
subst  [Type]
args
          Named (Bndr TyVar
tv ArgFlag
vis) -> ArgFlag -> TyConBndrVis
NamedTCB ArgFlag
vis TyConBndrVis -> [TyConBndrVis] -> [TyConBndrVis]
forall a. a -> [a] -> [a]
: Type -> TCvSubst -> [Type] -> [TyConBndrVis]
go Type
inner_kind TCvSubst
subst' [Type]
args
                 where
                    subst' :: TCvSubst
subst' = TCvSubst -> TyVar -> Type -> TCvSubst
extendTCvSubst TCvSubst
subst TyVar
tv Type
arg

      | Bool -> Bool
not (TCvSubst -> Bool
isEmptyTCvSubst TCvSubst
subst)
      = Type -> TCvSubst -> [Type] -> [TyConBndrVis]
go (HasCallStack => TCvSubst -> Type -> Type
TCvSubst -> Type -> Type
substTy TCvSubst
subst Type
fun_kind) TCvSubst
init_subst [Type]
all_args

      | Bool
otherwise
      = String -> SDoc -> [TyConBndrVis]
forall a. HasCallStack => String -> SDoc -> a
pprPanic String
"addTcbVisibilities" (TyCon -> SDoc
forall a. Outputable a => a -> SDoc
ppr TyCon
tc SDoc -> SDoc -> SDoc
<+> [Type] -> SDoc
forall a. Outputable a => a -> SDoc
ppr [Type]
orig_args)


{- Note [TyConBinders for the result kind signature of a data type]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Given
  data T (a::*) :: * -> forall k. k -> *
we want to generate the extra TyConBinders for T, so we finally get
  (a::*) (b::*) (k::*) (c::k)
The function etaExpandAlgTyCon generates these extra TyConBinders from
the result kind signature.

We need to take care to give the TyConBinders
  (a) OccNames that are fresh (because the TyConBinders of a TyCon
      must have distinct OccNames

  (b) Uniques that are fresh (obviously)

For (a) we need to avoid clashes with the tyvars declared by
the user before the "::"; in the above example that is 'a'.
And also see Note [Avoid name clashes for associated data types].

For (b) suppose we have
   data T :: forall k. k -> forall k. k -> *
where the two k's are identical even up to their uniques.  Surprisingly,
this can happen: see #14515.

It's reasonably easy to solve all this; just run down the list with a
substitution; hence the recursive 'go' function.  But it has to be
done.

Note [Avoid name clashes for associated data types]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Consider    class C a b where
               data D b :: * -> *
When typechecking the decl for D, we'll invent an extra type variable
for D, to fill out its kind.  Ideally we don't want this type variable
to be 'a', because when pretty printing we'll get
            class C a b where
               data D b a0
(NB: the tidying happens in the conversion to Iface syntax, which happens
as part of pretty-printing a TyThing.)

That's why we look in the LocalRdrEnv to see what's in scope. This is
important only to get nice-looking output when doing ":info C" in GHCi.
It isn't essential for correctness.


************************************************************************
*                                                                      *
             Partial signatures
*                                                                      *
************************************************************************

-}

tcHsPartialSigType
  :: UserTypeCtxt
  -> LHsSigWcType GhcRn       -- The type signature
  -> TcM ( [(Name, TcTyVar)]  -- Wildcards
         , Maybe TcType       -- Extra-constraints wildcard
         , [(Name,InvisTVBinder)] -- Original tyvar names, in correspondence with
                              --   the implicitly and explicitly bound type variables
         , TcThetaType        -- Theta part
         , TcType )           -- Tau part
-- See Note [Checking partial type signatures]
tcHsPartialSigType :: UserTypeCtxt
-> LHsSigWcType GhcRn
-> TcM
     ([(Name, TyVar)], Maybe Type, [(Name, InvisTVBinder)], [Type],
      Type)
tcHsPartialSigType UserTypeCtxt
ctxt LHsSigWcType GhcRn
sig_ty
  | HsWC { hswc_ext :: forall pass thing. HsWildCardBndrs pass thing -> XHsWC pass thing
hswc_ext  = XHsWC GhcRn (LHsSigType GhcRn)
sig_wcs, hswc_body :: forall pass thing. HsWildCardBndrs pass thing -> thing
hswc_body = LHsSigType GhcRn
sig_ty } <- LHsSigWcType GhcRn
sig_ty
  , L SrcSpanAnnA
_ (HsSig{sig_bndrs :: forall pass. HsSigType pass -> HsOuterSigTyVarBndrs pass
sig_bndrs = HsOuterSigTyVarBndrs GhcRn
hs_outer_bndrs, sig_body :: forall pass. HsSigType pass -> LHsType pass
sig_body = LHsType GhcRn
body_ty}) <- LHsSigType GhcRn
sig_ty
  , (Maybe (LHsContext GhcRn)
hs_ctxt, LHsType GhcRn
hs_tau) <- LHsType GhcRn -> (Maybe (LHsContext GhcRn), LHsType GhcRn)
forall (pass :: Pass).
LHsType (GhcPass pass)
-> (Maybe (LHsContext (GhcPass pass)), LHsType (GhcPass pass))
splitLHsQualTy LHsType GhcRn
body_ty
  = UserTypeCtxt
-> GenLocated SrcSpanAnnA (HsSigType GhcRn)
-> TcM
     ([(Name, TyVar)], Maybe Type, [(Name, InvisTVBinder)], [Type],
      Type)
-> TcM
     ([(Name, TyVar)], Maybe Type, [(Name, InvisTVBinder)], [Type],
      Type)
forall hs_ty a.
Outputable hs_ty =>
UserTypeCtxt -> LocatedA hs_ty -> TcM a -> TcM a
addSigCtxt UserTypeCtxt
ctxt GenLocated SrcSpanAnnA (HsSigType GhcRn)
LHsSigType GhcRn
sig_ty (TcM
   ([(Name, TyVar)], Maybe Type, [(Name, InvisTVBinder)], [Type],
    Type)
 -> TcM
      ([(Name, TyVar)], Maybe Type, [(Name, InvisTVBinder)], [Type],
       Type))
-> TcM
     ([(Name, TyVar)], Maybe Type, [(Name, InvisTVBinder)], [Type],
      Type)
-> TcM
     ([(Name, TyVar)], Maybe Type, [(Name, InvisTVBinder)], [Type],
      Type)
forall a b. (a -> b) -> a -> b
$
    do { TcTyMode
mode <- TypeOrKind -> HoleMode -> TcM TcTyMode
mkHoleMode TypeOrKind
TypeLevel HoleMode
HM_Sig
       ; (HsOuterTyVarBndrs Specificity GhcTc
outer_bndrs, ([(Name, TyVar)]
wcs, Maybe Type
wcx, [Type]
theta, Type
tau))
            <- String
-> TcM
     (HsOuterTyVarBndrs Specificity GhcTc,
      ([(Name, TyVar)], Maybe Type, [Type], Type))
-> TcM
     (HsOuterTyVarBndrs Specificity GhcTc,
      ([(Name, TyVar)], Maybe Type, [Type], Type))
forall a. String -> TcM a -> TcM a
solveEqualities String
"tcHsPartialSigType" (TcM
   (HsOuterTyVarBndrs Specificity GhcTc,
    ([(Name, TyVar)], Maybe Type, [Type], Type))
 -> TcM
      (HsOuterTyVarBndrs Specificity GhcTc,
       ([(Name, TyVar)], Maybe Type, [Type], Type)))
-> TcM
     (HsOuterTyVarBndrs Specificity GhcTc,
      ([(Name, TyVar)], Maybe Type, [Type], Type))
-> TcM
     (HsOuterTyVarBndrs Specificity GhcTc,
      ([(Name, TyVar)], Maybe Type, [Type], Type))
forall a b. (a -> b) -> a -> b
$
               -- See Note [Failure in local type signatures]
               HsQTvsRn
-> ([(Name, TyVar)]
    -> TcM
         (HsOuterTyVarBndrs Specificity GhcTc,
          ([(Name, TyVar)], Maybe Type, [Type], Type)))
-> TcM
     (HsOuterTyVarBndrs Specificity GhcTc,
      ([(Name, TyVar)], Maybe Type, [Type], Type))
forall a. HsQTvsRn -> ([(Name, TyVar)] -> TcM a) -> TcM a
bindNamedWildCardBinders HsQTvsRn
XHsWC GhcRn (LHsSigType GhcRn)
sig_wcs             (([(Name, TyVar)]
  -> TcM
       (HsOuterTyVarBndrs Specificity GhcTc,
        ([(Name, TyVar)], Maybe Type, [Type], Type)))
 -> TcM
      (HsOuterTyVarBndrs Specificity GhcTc,
       ([(Name, TyVar)], Maybe Type, [Type], Type)))
-> ([(Name, TyVar)]
    -> TcM
         (HsOuterTyVarBndrs Specificity GhcTc,
          ([(Name, TyVar)], Maybe Type, [Type], Type)))
-> TcM
     (HsOuterTyVarBndrs Specificity GhcTc,
      ([(Name, TyVar)], Maybe Type, [Type], Type))
forall a b. (a -> b) -> a -> b
$ \ [(Name, TyVar)]
wcs ->
               TcTyMode
-> HsOuterSigTyVarBndrs GhcRn
-> TcM ([(Name, TyVar)], Maybe Type, [Type], Type)
-> TcM
     (HsOuterTyVarBndrs Specificity GhcTc,
      ([(Name, TyVar)], Maybe Type, [Type], Type))
forall a.
TcTyMode
-> HsOuterSigTyVarBndrs GhcRn
-> TcM a
-> TcM (HsOuterTyVarBndrs Specificity GhcTc, a)
bindOuterSigTKBndrs_Tv_M TcTyMode
mode HsOuterSigTyVarBndrs GhcRn
hs_outer_bndrs (TcM ([(Name, TyVar)], Maybe Type, [Type], Type)
 -> TcM
      (HsOuterTyVarBndrs Specificity GhcTc,
       ([(Name, TyVar)], Maybe Type, [Type], Type)))
-> TcM ([(Name, TyVar)], Maybe Type, [Type], Type)
-> TcM
     (HsOuterTyVarBndrs Specificity GhcTc,
      ([(Name, TyVar)], Maybe Type, [Type], Type))
forall a b. (a -> b) -> a -> b
$
               do {   -- Instantiate the type-class context; but if there
                      -- is an extra-constraints wildcard, just discard it here
                    ([Type]
theta, Maybe Type
wcx) <- TcTyMode -> Maybe (LHsContext GhcRn) -> TcM ([Type], Maybe Type)
tcPartialContext TcTyMode
mode Maybe (LHsContext GhcRn)
hs_ctxt

                  ; Type
ek <- TcM Type
newOpenTypeKind
                  ; Type
tau <- LHsType GhcRn -> TcM Type -> TcM Type
forall a. LHsType GhcRn -> TcM a -> TcM a
addTypeCtxt LHsType GhcRn
hs_tau (TcM Type -> TcM Type) -> TcM Type -> TcM Type
forall a b. (a -> b) -> a -> b
$
                           TcTyMode -> LHsType GhcRn -> Type -> TcM Type
tc_lhs_type TcTyMode
mode LHsType GhcRn
hs_tau Type
ek

                  ; ([(Name, TyVar)], Maybe Type, [Type], Type)
-> TcM ([(Name, TyVar)], Maybe Type, [Type], Type)
forall (m :: * -> *) a. Monad m => a -> m a
return ([(Name, TyVar)]
wcs, Maybe Type
wcx, [Type]
theta, Type
tau) }

       ; String -> SDoc -> TcM ()
traceTc String
"tcHsPartialSigType 2" SDoc
empty
       ; [InvisTVBinder]
outer_tv_bndrs <- HsOuterTyVarBndrs Specificity GhcTc -> TcM [InvisTVBinder]
scopedSortOuter HsOuterTyVarBndrs Specificity GhcTc
outer_bndrs
       ; String -> SDoc -> TcM ()
traceTc String
"tcHsPartialSigType 3" SDoc
empty

         -- No kind-generalization here:
       ; Type -> TcM ()
kindGeneralizeNone ([InvisTVBinder] -> Type -> Type
mkInvisForAllTys [InvisTVBinder]
outer_tv_bndrs (Type -> Type) -> Type -> Type
forall a b. (a -> b) -> a -> b
$
                             [Type] -> Type -> Type
mkPhiTy [Type]
theta (Type -> Type) -> Type -> Type
forall a b. (a -> b) -> a -> b
$
                             Type
tau)

       -- Spit out the wildcards (including the extra-constraints one)
       -- as "hole" constraints, so that they'll be reported if necessary
       -- See Note [Extra-constraint holes in partial type signatures]
       ; ((Name, TyVar) -> TcM ()) -> [(Name, TyVar)] -> TcM ()
forall (t :: * -> *) (m :: * -> *) a b.
(Foldable t, Monad m) =>
(a -> m b) -> t a -> m ()
mapM_ (Name, TyVar) -> TcM ()
emitNamedTypeHole [(Name, TyVar)]
wcs

       -- Zonk, so that any nested foralls can "see" their occurrences
       -- See Note [Checking partial type signatures], and in particular
       -- Note [Levels for wildcards]
       ; [InvisTVBinder]
outer_tv_bndrs <- (InvisTVBinder -> IOEnv (Env TcGblEnv TcLclEnv) InvisTVBinder)
-> [InvisTVBinder] -> TcM [InvisTVBinder]
forall (t :: * -> *) (m :: * -> *) a b.
(Traversable t, Monad m) =>
(a -> m b) -> t a -> m (t b)
mapM InvisTVBinder -> IOEnv (Env TcGblEnv TcLclEnv) InvisTVBinder
forall spec. VarBndr TyVar spec -> TcM (VarBndr TyVar spec)
zonkInvisTVBinder [InvisTVBinder]
outer_tv_bndrs
       ; [Type]
theta          <- (Type -> TcM Type) -> [Type] -> TcM [Type]
forall (t :: * -> *) (m :: * -> *) a b.
(Traversable t, Monad m) =>
(a -> m b) -> t a -> m (t b)
mapM Type -> TcM Type
zonkTcType [Type]
theta
       ; Type
tau            <- Type -> TcM Type
zonkTcType Type
tau

         -- We return a proper (Name,InvisTVBinder) environment, to be sure that
         -- we bring the right name into scope in the function body.
         -- Test case: partial-sigs/should_compile/LocalDefinitionBug
       ; let outer_bndr_names :: [Name]
             outer_bndr_names :: HsQTvsRn
outer_bndr_names = HsOuterSigTyVarBndrs GhcRn -> HsQTvsRn
forall flag. HsOuterTyVarBndrs flag GhcRn -> HsQTvsRn
hsOuterTyVarNames HsOuterSigTyVarBndrs GhcRn
hs_outer_bndrs
             tv_prs :: [(Name,InvisTVBinder)]
             tv_prs :: [(Name, InvisTVBinder)]
tv_prs = HsQTvsRn
outer_bndr_names HsQTvsRn -> [InvisTVBinder] -> [(Name, InvisTVBinder)]
forall a b. [a] -> [b] -> [(a, b)]
`zip` [InvisTVBinder]
outer_tv_bndrs

      -- NB: checkValidType on the final inferred type will be
      --     done later by checkInferredPolyId.  We can't do it
      --     here because we don't have a complete type to check

       ; String -> SDoc -> TcM ()
traceTc String
"tcHsPartialSigType" ([(Name, InvisTVBinder)] -> SDoc
forall a. Outputable a => a -> SDoc
ppr [(Name, InvisTVBinder)]
tv_prs)
       ; ([(Name, TyVar)], Maybe Type, [(Name, InvisTVBinder)], [Type],
 Type)
-> TcM
     ([(Name, TyVar)], Maybe Type, [(Name, InvisTVBinder)], [Type],
      Type)
forall (m :: * -> *) a. Monad m => a -> m a
return ([(Name, TyVar)]
wcs, Maybe Type
wcx, [(Name, InvisTVBinder)]
tv_prs, [Type]
theta, Type
tau) }

tcPartialContext :: TcTyMode -> Maybe (LHsContext GhcRn) -> TcM (TcThetaType, Maybe TcType)
tcPartialContext :: TcTyMode -> Maybe (LHsContext GhcRn) -> TcM ([Type], Maybe Type)
tcPartialContext TcTyMode
_ Maybe (LHsContext GhcRn)
Nothing = ([Type], Maybe Type) -> TcM ([Type], Maybe Type)
forall (m :: * -> *) a. Monad m => a -> m a
return ([], Maybe Type
forall a. Maybe a
Nothing)
tcPartialContext TcTyMode
mode (Just (L SrcSpanAnnC
_ [GenLocated SrcSpanAnnA (HsType GhcRn)]
hs_theta))
  | Just ([GenLocated SrcSpanAnnA (HsType GhcRn)]
hs_theta1, GenLocated SrcSpanAnnA (HsType GhcRn)
hs_ctxt_last) <- [GenLocated SrcSpanAnnA (HsType GhcRn)]
-> Maybe
     ([GenLocated SrcSpanAnnA (HsType GhcRn)],
      GenLocated SrcSpanAnnA (HsType GhcRn))
forall a. [a] -> Maybe ([a], a)
snocView [GenLocated SrcSpanAnnA (HsType GhcRn)]
hs_theta
  , L SrcSpanAnnA
wc_loc ty :: HsType GhcRn
ty@(HsWildCardTy XWildCardTy GhcRn
_) <- LHsType GhcRn -> LHsType GhcRn
forall (p :: Pass). LHsType (GhcPass p) -> LHsType (GhcPass p)
ignoreParens GenLocated SrcSpanAnnA (HsType GhcRn)
LHsType GhcRn
hs_ctxt_last
  = do { Type
wc_tv_ty <- SrcSpanAnnA -> TcM Type -> TcM Type
forall ann a. SrcSpanAnn' ann -> TcRn a -> TcRn a
setSrcSpanA SrcSpanAnnA
wc_loc (TcM Type -> TcM Type) -> TcM Type -> TcM Type
forall a b. (a -> b) -> a -> b
$
                     IsExtraConstraint -> TcTyMode -> HsType GhcRn -> Type -> TcM Type
tcAnonWildCardOcc IsExtraConstraint
YesExtraConstraint TcTyMode
mode HsType GhcRn
ty Type
constraintKind
       ; [Type]
theta <- (GenLocated SrcSpanAnnA (HsType GhcRn) -> TcM Type)
-> [GenLocated SrcSpanAnnA (HsType GhcRn)] -> TcM [Type]
forall (t :: * -> *) (m :: * -> *) a b.
(Traversable t, Monad m) =>
(a -> m b) -> t a -> m (t b)
mapM (TcTyMode -> LHsType GhcRn -> TcM Type
tc_lhs_pred TcTyMode
mode) [GenLocated SrcSpanAnnA (HsType GhcRn)]
hs_theta1
       ; ([Type], Maybe Type) -> TcM ([Type], Maybe Type)
forall (m :: * -> *) a. Monad m => a -> m a
return ([Type]
theta, Type -> Maybe Type
forall a. a -> Maybe a
Just Type
wc_tv_ty) }
  | Bool
otherwise
  = do { [Type]
theta <- (GenLocated SrcSpanAnnA (HsType GhcRn) -> TcM Type)
-> [GenLocated SrcSpanAnnA (HsType GhcRn)] -> TcM [Type]
forall (t :: * -> *) (m :: * -> *) a b.
(Traversable t, Monad m) =>
(a -> m b) -> t a -> m (t b)
mapM (TcTyMode -> LHsType GhcRn -> TcM Type
tc_lhs_pred TcTyMode
mode) [GenLocated SrcSpanAnnA (HsType GhcRn)]
hs_theta
       ; ([Type], Maybe Type) -> TcM ([Type], Maybe Type)
forall (m :: * -> *) a. Monad m => a -> m a
return ([Type]
theta, Maybe Type
forall a. Maybe a
Nothing) }

{- Note [Checking partial type signatures]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
This Note is about tcHsPartialSigType.  See also
Note [Recipe for checking a signature]

When we have a partial signature like
   f :: forall a. a -> _
we do the following

* tcHsPartialSigType does not make quantified type (forall a. blah)
  and then instantiate it -- it makes no sense to instantiate a type
  with wildcards in it.  Rather, tcHsPartialSigType just returns the
  'a' and the 'blah' separately.

  Nor, for the same reason, do we push a level in tcHsPartialSigType.

* We instantiate 'a' to a unification variable, a TyVarTv, and /not/
  a skolem; hence the "_Tv" in bindExplicitTKBndrs_Tv.  Consider
    f :: forall a. a -> _
    g :: forall b. _ -> b
    f = g
    g = f
  They are typechecked as a recursive group, with monomorphic types,
  so 'a' and 'b' will get unified together.  Very like kind inference
  for mutually recursive data types (sans CUSKs or SAKS); see
  Note [Cloning for type variable binders]

* In GHC.Tc.Gen.Sig.tcUserSigType we return a PartialSig, which (unlike
  the companion CompleteSig) contains the original, as-yet-unchecked
  source-code LHsSigWcType

* Then, for f and g /separately/, we call tcInstSig, which in turn
  call tchsPartialSig (defined near this Note).  It kind-checks the
  LHsSigWcType, creating fresh unification variables for each "_"
  wildcard.  It's important that the wildcards for f and g are distinct
  because they might get instantiated completely differently.  E.g.
     f,g :: forall a. a -> _
     f x = a
     g x = True
  It's really as if we'd written two distinct signatures.

* Nested foralls. See Note [Levels for wildcards]

* Just as for ordinary signatures, we must solve local equalities and
  zonk the type after kind-checking it, to ensure that all the nested
  forall binders can "see" their occurrenceds

  Just as for ordinary signatures, this zonk also gets any Refl casts
  out of the way of instantiation.  Example: #18008 had
       foo :: (forall a. (Show a => blah) |> Refl) -> _
  and that Refl cast messed things up.  See #18062.

Note [Levels for wildcards]
~~~~~~~~~~~~~~~~~~~~~~~~~~~
Consider
     f :: forall b. (forall a. a -> _) -> b
We do /not/ allow the "_" to be instantiated to 'a'; although we do
(as before) allow it to be instantiated to the (top level) 'b'.
Why not?  Suppose
   f x = (x True, x 'c')

During typecking the RHS we must instantiate that (forall a. a -> _),
so we must know /precisely/ where all the a's are; they must not be
hidden under (possibly-not-yet-filled-in) unification variables!

We achieve this as follows:

- For /named/ wildcards such sas
     g :: forall b. (forall la. a -> _x) -> b
  there is no problem: we create them at the outer level (ie the
  ambient level of the signature itself), and push the level when we
  go inside a forall.  So now the unification variable for the "_x"
  can't unify with skolem 'a'.

- For /anonymous/ wildcards, such as 'f' above, we carry the ambient
  level of the signature to the hole in the TcLevel part of the
  mode_holes field of TcTyMode.  Then, in tcAnonWildCardOcc we us that
  level (and /not/ the level ambient at the occurrence of "_") to
  create the unification variable for the wildcard.  That is the sole
  purpose of the TcLevel in the mode_holes field: to transport the
  ambient level of the signature down to the anonymous wildcard
  occurrences.

Note [Extra-constraint holes in partial type signatures]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Consider
  f :: (_) => a -> a
  f x = ...

* The renamer leaves '_' untouched.

* Then, in tcHsPartialSigType, we make a new hole TcTyVar, in
  tcWildCardBinders.

* GHC.Tc.Gen.Bind.chooseInferredQuantifiers fills in that hole TcTyVar
  with the inferred constraints, e.g. (Eq a, Show a)

* GHC.Tc.Errors.mkHoleError finally reports the error.

An annoying difficulty happens if there are more than 64 inferred
constraints. Then we need to fill in the TcTyVar with (say) a 70-tuple.
Where do we find the TyCon?  For good reasons we only have constraint
tuples up to 62 (see Note [How tuples work] in GHC.Builtin.Types).  So how
can we make a 70-tuple?  This was the root cause of #14217.

It's incredibly tiresome, because we only need this type to fill
in the hole, to communicate to the error reporting machinery.  Nothing
more.  So I use a HACK:

* I make an /ordinary/ tuple of the constraints, in
  GHC.Tc.Gen.Bind.chooseInferredQuantifiers. This is ill-kinded because
  ordinary tuples can't contain constraints, but it works fine. And for
  ordinary tuples we don't have the same limit as for constraint
  tuples (which need selectors and an associated class).

* Because it is ill-kinded, it trips an assert in writeMetaTyVar,
  so now I disable the assertion if we are writing a type of
  kind Constraint.  (That seldom/never normally happens so we aren't
  losing much.)

Result works fine, but it may eventually bite us.

See also Note [Do not simplify ConstraintHoles] in GHC.Tc.Solver for
information about how these are printed.

************************************************************************
*                                                                      *
      Pattern signatures (i.e signatures that occur in patterns)
*                                                                      *
********************************************************************* -}

tcHsPatSigType :: UserTypeCtxt
               -> HoleMode -- HM_Sig when in a SigPat, HM_TyAppPat when in a ConPat checking type applications.
               -> HsPatSigType GhcRn          -- The type signature
               -> ContextKind                -- What kind is expected
               -> TcM ( [(Name, TcTyVar)]     -- Wildcards
                      , [(Name, TcTyVar)]     -- The new bit of type environment, binding
                                              -- the scoped type variables
                      , TcType)       -- The type
-- Used for type-checking type signatures in
-- (a) patterns           e.g  f (x::Int) = e
-- (b) RULE forall bndrs  e.g. forall (x::Int). f x = x
-- See Note [Pattern signature binders and scoping] in GHC.Hs.Type
--
-- This may emit constraints
-- See Note [Recipe for checking a signature]
tcHsPatSigType :: UserTypeCtxt
-> HoleMode
-> HsPatSigType GhcRn
-> ContextKind
-> TcM ([(Name, TyVar)], [(Name, TyVar)], Type)
tcHsPatSigType UserTypeCtxt
ctxt HoleMode
hole_mode
  (HsPS { hsps_ext :: forall pass. HsPatSigType pass -> XHsPS pass
hsps_ext  = HsPSRn { hsps_nwcs :: HsPSRn -> HsQTvsRn
hsps_nwcs = HsQTvsRn
sig_wcs, hsps_imp_tvs :: HsPSRn -> HsQTvsRn
hsps_imp_tvs = HsQTvsRn
sig_ns }
        , hsps_body :: forall pass. HsPatSigType pass -> LHsType pass
hsps_body = LHsType GhcRn
hs_ty })
  ContextKind
ctxt_kind
  = UserTypeCtxt
-> GenLocated SrcSpanAnnA (HsType GhcRn)
-> TcM ([(Name, TyVar)], [(Name, TyVar)], Type)
-> TcM ([(Name, TyVar)], [(Name, TyVar)], Type)
forall hs_ty a.
Outputable hs_ty =>
UserTypeCtxt -> LocatedA hs_ty -> TcM a -> TcM a
addSigCtxt UserTypeCtxt
ctxt GenLocated SrcSpanAnnA (HsType GhcRn)
LHsType GhcRn
hs_ty (TcM ([(Name, TyVar)], [(Name, TyVar)], Type)
 -> TcM ([(Name, TyVar)], [(Name, TyVar)], Type))
-> TcM ([(Name, TyVar)], [(Name, TyVar)], Type)
-> TcM ([(Name, TyVar)], [(Name, TyVar)], Type)
forall a b. (a -> b) -> a -> b
$
    do { [(Name, TyVar)]
sig_tkv_prs <- (Name -> IOEnv (Env TcGblEnv TcLclEnv) (Name, TyVar))
-> HsQTvsRn -> IOEnv (Env TcGblEnv TcLclEnv) [(Name, TyVar)]
forall (t :: * -> *) (m :: * -> *) a b.
(Traversable t, Monad m) =>
(a -> m b) -> t a -> m (t b)
mapM Name -> IOEnv (Env TcGblEnv TcLclEnv) (Name, TyVar)
new_implicit_tv HsQTvsRn
sig_ns
       ; TcTyMode
mode <- TypeOrKind -> HoleMode -> TcM TcTyMode
mkHoleMode TypeOrKind
TypeLevel HoleMode
hole_mode
       ; ([(Name, TyVar)]
wcs, Type
sig_ty)
            <- LHsType GhcRn
-> TcM ([(Name, TyVar)], Type) -> TcM ([(Name, TyVar)], Type)
forall a. LHsType GhcRn -> TcM a -> TcM a
addTypeCtxt LHsType GhcRn
hs_ty                     (TcM ([(Name, TyVar)], Type) -> TcM ([(Name, TyVar)], Type))
-> TcM ([(Name, TyVar)], Type) -> TcM ([(Name, TyVar)], Type)
forall a b. (a -> b) -> a -> b
$
               String
-> TcM ([(Name, TyVar)], Type) -> TcM ([(Name, TyVar)], Type)
forall a. String -> TcM a -> TcM a
solveEqualities String
"tcHsPatSigType" (TcM ([(Name, TyVar)], Type) -> TcM ([(Name, TyVar)], Type))
-> TcM ([(Name, TyVar)], Type) -> TcM ([(Name, TyVar)], Type)
forall a b. (a -> b) -> a -> b
$
                 -- See Note [Failure in local type signatures]
                 -- and c.f #16033
               HsQTvsRn
-> ([(Name, TyVar)] -> TcM ([(Name, TyVar)], Type))
-> TcM ([(Name, TyVar)], Type)
forall a. HsQTvsRn -> ([(Name, TyVar)] -> TcM a) -> TcM a
bindNamedWildCardBinders HsQTvsRn
sig_wcs (([(Name, TyVar)] -> TcM ([(Name, TyVar)], Type))
 -> TcM ([(Name, TyVar)], Type))
-> ([(Name, TyVar)] -> TcM ([(Name, TyVar)], Type))
-> TcM ([(Name, TyVar)], Type)
forall a b. (a -> b) -> a -> b
$ \ [(Name, TyVar)]
wcs ->
               [(Name, TyVar)]
-> TcM ([(Name, TyVar)], Type) -> TcM ([(Name, TyVar)], Type)
forall r. [(Name, TyVar)] -> TcM r -> TcM r
tcExtendNameTyVarEnv [(Name, TyVar)]
sig_tkv_prs (TcM ([(Name, TyVar)], Type) -> TcM ([(Name, TyVar)], Type))
-> TcM ([(Name, TyVar)], Type) -> TcM ([(Name, TyVar)], Type)
forall a b. (a -> b) -> a -> b
$
               do { Type
ek     <- ContextKind -> TcM Type
newExpectedKind ContextKind
ctxt_kind
                  ; Type
sig_ty <- TcTyMode -> LHsType GhcRn -> Type -> TcM Type
tc_lhs_type TcTyMode
mode LHsType GhcRn
hs_ty Type
ek
                  ; ([(Name, TyVar)], Type) -> TcM ([(Name, TyVar)], Type)
forall (m :: * -> *) a. Monad m => a -> m a
return ([(Name, TyVar)]
wcs, Type
sig_ty) }

        ; ((Name, TyVar) -> TcM ()) -> [(Name, TyVar)] -> TcM ()
forall (t :: * -> *) (m :: * -> *) a b.
(Foldable t, Monad m) =>
(a -> m b) -> t a -> m ()
mapM_ (Name, TyVar) -> TcM ()
emitNamedTypeHole [(Name, TyVar)]
wcs

          -- sig_ty might have tyvars that are at a higher TcLevel (if hs_ty
          -- contains a forall). Promote these.
          -- Ex: f (x :: forall a. Proxy a -> ()) = ... x ...
          -- When we instantiate x, we have to compare the kind of the argument
          -- to a's kind, which will be a metavariable.
          -- kindGeneralizeNone does this:
        ; Type -> TcM ()
kindGeneralizeNone Type
sig_ty
        ; Type
sig_ty <- Type -> TcM Type
zonkTcType Type
sig_ty
        ; UserTypeCtxt -> Type -> TcM ()
checkValidType UserTypeCtxt
ctxt Type
sig_ty

        ; String -> SDoc -> TcM ()
traceTc String
"tcHsPatSigType" ([(Name, TyVar)] -> SDoc
forall a. Outputable a => a -> SDoc
ppr [(Name, TyVar)]
sig_tkv_prs)
        ; ([(Name, TyVar)], [(Name, TyVar)], Type)
-> TcM ([(Name, TyVar)], [(Name, TyVar)], Type)
forall (m :: * -> *) a. Monad m => a -> m a
return ([(Name, TyVar)]
wcs, [(Name, TyVar)]
sig_tkv_prs, Type
sig_ty) }
  where
    new_implicit_tv :: Name -> IOEnv (Env TcGblEnv TcLclEnv) (Name, TyVar)
new_implicit_tv Name
name
      = do { Type
kind <- TcM Type
newMetaKindVar
           ; TyVar
tv   <- case UserTypeCtxt
ctxt of
                       RuleSigCtxt {} -> Name -> Type -> IOEnv (Env TcGblEnv TcLclEnv) TyVar
newSkolemTyVar Name
name Type
kind
                       UserTypeCtxt
_              -> Name -> Type -> IOEnv (Env TcGblEnv TcLclEnv) TyVar
newPatSigTyVar Name
name Type
kind
                       -- See Note [Typechecking pattern signature binders]
             -- NB: tv's Name may be fresh (in the case of newPatSigTyVar)
           ; (Name, TyVar) -> IOEnv (Env TcGblEnv TcLclEnv) (Name, TyVar)
forall (m :: * -> *) a. Monad m => a -> m a
return (Name
name, TyVar
tv) }

{- Note [Typechecking pattern signature binders]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
See also Note [Type variables in the type environment] in GHC.Tc.Utils.
Consider

  data T where
    MkT :: forall a. a -> (a -> Int) -> T

  f :: T -> ...
  f (MkT x (f :: b -> c)) = <blah>

Here
 * The pattern (MkT p1 p2) creates a *skolem* type variable 'a_sk',
   It must be a skolem so that it retains its identity, and
   GHC.Tc.Errors.getSkolemInfo can thereby find the binding site for the skolem.

 * The type signature pattern (f :: b -> c) makes fresh meta-tyvars
   beta and gamma (TauTvs), and binds "b" :-> beta, "c" :-> gamma in the
   environment

 * Then unification makes beta := a_sk, gamma := Int
   That's why we must make beta and gamma a MetaTv,
   not a SkolemTv, so that it can unify to a_sk (or Int, respectively).

 * Finally, in '<blah>' we have the envt "b" :-> beta, "c" :-> gamma,
   so we return the pairs ("b" :-> beta, "c" :-> gamma) from tcHsPatSigType,

Another example (#13881):
   fl :: forall (l :: [a]). Sing l -> Sing l
   fl (SNil :: Sing (l :: [y])) = SNil
When we reach the pattern signature, 'l' is in scope from the
outer 'forall':
   "a" :-> a_sk :: *
   "l" :-> l_sk :: [a_sk]
We make up a fresh meta-TauTv, y_sig, for 'y', and kind-check
the pattern signature
   Sing (l :: [y])
That unifies y_sig := a_sk.  We return from tcHsPatSigType with
the pair ("y" :-> y_sig).

For RULE binders, though, things are a bit different (yuk).
  RULE "foo" forall (x::a) (y::[a]).  f x y = ...
Here this really is the binding site of the type variable so we'd like
to use a skolem, so that we get a complaint if we unify two of them
together.  Hence the new_implicit_tv function in tcHsPatSigType.


************************************************************************
*                                                                      *
        Checking kinds
*                                                                      *
************************************************************************

-}

unifyKinds :: [LHsType GhcRn] -> [(TcType, TcKind)] -> TcM ([TcType], TcKind)
unifyKinds :: [LHsType GhcRn] -> [(Type, Type)] -> TcM ([Type], Type)
unifyKinds [LHsType GhcRn]
rn_tys [(Type, Type)]
act_kinds
  = do { Type
kind <- TcM Type
newMetaKindVar
       ; let check :: GenLocated SrcSpanAnnA (HsType GhcRn) -> (Type, Type) -> TcM Type
check GenLocated SrcSpanAnnA (HsType GhcRn)
rn_ty (Type
ty, Type
act_kind)
               = HasDebugCallStack =>
HsType GhcRn -> Type -> Type -> Type -> TcM Type
HsType GhcRn -> Type -> Type -> Type -> TcM Type
checkExpectedKind (GenLocated SrcSpanAnnA (HsType GhcRn) -> HsType GhcRn
forall l e. GenLocated l e -> e
unLoc GenLocated SrcSpanAnnA (HsType GhcRn)
rn_ty) Type
ty Type
act_kind Type
kind
       ; [Type]
tys' <- (GenLocated SrcSpanAnnA (HsType GhcRn) -> (Type, Type) -> TcM Type)
-> [GenLocated SrcSpanAnnA (HsType GhcRn)]
-> [(Type, Type)]
-> TcM [Type]
forall (m :: * -> *) a b c.
Applicative m =>
(a -> b -> m c) -> [a] -> [b] -> m [c]
zipWithM GenLocated SrcSpanAnnA (HsType GhcRn) -> (Type, Type) -> TcM Type
check [GenLocated SrcSpanAnnA (HsType GhcRn)]
[LHsType GhcRn]
rn_tys [(Type, Type)]
act_kinds
       ; ([Type], Type) -> TcM ([Type], Type)
forall (m :: * -> *) a. Monad m => a -> m a
return ([Type]
tys', Type
kind) }

{-
************************************************************************
*                                                                      *
        Sort checking kinds
*                                                                      *
************************************************************************

tcLHsKindSig converts a user-written kind to an internal, sort-checked kind.
It does sort checking and desugaring at the same time, in one single pass.
-}

tcLHsKindSig :: UserTypeCtxt -> LHsKind GhcRn -> TcM Kind
tcLHsKindSig :: UserTypeCtxt -> LHsType GhcRn -> TcM Type
tcLHsKindSig UserTypeCtxt
ctxt LHsType GhcRn
hs_kind
  = TcTyMode -> UserTypeCtxt -> LHsType GhcRn -> TcM Type
tc_lhs_kind_sig TcTyMode
kindLevelMode UserTypeCtxt
ctxt LHsType GhcRn
hs_kind

tc_lhs_kind_sig :: TcTyMode -> UserTypeCtxt -> LHsKind GhcRn -> TcM Kind
tc_lhs_kind_sig :: TcTyMode -> UserTypeCtxt -> LHsType GhcRn -> TcM Type
tc_lhs_kind_sig TcTyMode
mode UserTypeCtxt
ctxt LHsType GhcRn
hs_kind
-- See  Note [Recipe for checking a signature] in GHC.Tc.Gen.HsType
-- Result is zonked
  = do { Type
kind <- SDoc -> TcM Type -> TcM Type
forall a. SDoc -> TcM a -> TcM a
addErrCtxt (String -> SDoc
text String
"In the kind" SDoc -> SDoc -> SDoc
<+> SDoc -> SDoc
quotes (GenLocated SrcSpanAnnA (HsType GhcRn) -> SDoc
forall a. Outputable a => a -> SDoc
ppr GenLocated SrcSpanAnnA (HsType GhcRn)
LHsType GhcRn
hs_kind)) (TcM Type -> TcM Type) -> TcM Type -> TcM Type
forall a b. (a -> b) -> a -> b
$
                 String -> TcM Type -> TcM Type
forall a. String -> TcM a -> TcM a
solveEqualities String
"tcLHsKindSig" (TcM Type -> TcM Type) -> TcM Type -> TcM Type
forall a b. (a -> b) -> a -> b
$
                 TcTyMode -> LHsType GhcRn -> Type -> TcM Type
tc_lhs_type TcTyMode
mode LHsType GhcRn
hs_kind Type
liftedTypeKind
       ; String -> SDoc -> TcM ()
traceTc String
"tcLHsKindSig" (GenLocated SrcSpanAnnA (HsType GhcRn) -> SDoc
forall a. Outputable a => a -> SDoc
ppr GenLocated SrcSpanAnnA (HsType GhcRn)
LHsType GhcRn
hs_kind SDoc -> SDoc -> SDoc
$$ Type -> SDoc
forall a. Outputable a => a -> SDoc
ppr Type
kind)
       -- No generalization:
       ; Type -> TcM ()
kindGeneralizeNone Type
kind
       ; Type
kind <- Type -> TcM Type
zonkTcType Type
kind
         -- This zonk is very important in the case of higher rank kinds
         -- E.g. #13879    f :: forall (p :: forall z (y::z). <blah>).
         --                          <more blah>
         --      When instantiating p's kind at occurrences of p in <more blah>
         --      it's crucial that the kind we instantiate is fully zonked,
         --      else we may fail to substitute properly

       ; UserTypeCtxt -> Type -> TcM ()
checkValidType UserTypeCtxt
ctxt Type
kind
       ; String -> SDoc -> TcM ()
traceTc String
"tcLHsKindSig2" (Type -> SDoc
forall a. Outputable a => a -> SDoc
ppr Type
kind)
       ; Type -> TcM Type
forall (m :: * -> *) a. Monad m => a -> m a
return Type
kind }

promotionErr :: Name -> PromotionErr -> TcM a
promotionErr :: forall a. Name -> PromotionErr -> TcM a
promotionErr Name
name PromotionErr
err
  = SDoc -> TcM a
forall a. SDoc -> TcM a
failWithTc (SDoc -> Arity -> SDoc -> SDoc
hang (PromotionErr -> SDoc
pprPECategory PromotionErr
err SDoc -> SDoc -> SDoc
<+> SDoc -> SDoc
quotes (Name -> SDoc
forall a. Outputable a => a -> SDoc
ppr Name
name) SDoc -> SDoc -> SDoc
<+> String -> SDoc
text String
"cannot be used here")
                   Arity
2 (SDoc -> SDoc
parens SDoc
reason))
  where
    reason :: SDoc
reason = case PromotionErr
err of
               ConstrainedDataConPE Type
pred
                              -> String -> SDoc
text String
"it has an unpromotable context"
                                 SDoc -> SDoc -> SDoc
<+> SDoc -> SDoc
quotes (Type -> SDoc
forall a. Outputable a => a -> SDoc
ppr Type
pred)
               PromotionErr
FamDataConPE   -> String -> SDoc
text String
"it comes from a data family instance"
               PromotionErr
NoDataKindsTC  -> String -> SDoc
text String
"perhaps you intended to use DataKinds"
               PromotionErr
NoDataKindsDC  -> String -> SDoc
text String
"perhaps you intended to use DataKinds"
               PromotionErr
PatSynPE       -> String -> SDoc
text String
"pattern synonyms cannot be promoted"
               PromotionErr
RecDataConPE   -> SDoc
same_rec_group_msg
               PromotionErr
ClassPE        -> SDoc
same_rec_group_msg
               PromotionErr
TyConPE        -> SDoc
same_rec_group_msg

    same_rec_group_msg :: SDoc
same_rec_group_msg = String -> SDoc
text String
"it is defined and used in the same recursive group"

{-
************************************************************************
*                                                                      *
          Error messages and such
*                                                                      *
************************************************************************
-}


-- | Make an appropriate message for an error in a function argument.
-- Used for both expressions and types.
funAppCtxt :: (Outputable fun, Outputable arg) => fun -> arg -> Int -> SDoc
funAppCtxt :: forall fun arg.
(Outputable fun, Outputable arg) =>
fun -> arg -> Arity -> SDoc
funAppCtxt fun
fun arg
arg Arity
arg_no
  = SDoc -> Arity -> SDoc -> SDoc
hang ([SDoc] -> SDoc
hsep [ String -> SDoc
text String
"In the", Arity -> SDoc
speakNth Arity
arg_no, PtrString -> SDoc
ptext (String -> PtrString
sLit String
"argument of"),
                    SDoc -> SDoc
quotes (fun -> SDoc
forall a. Outputable a => a -> SDoc
ppr fun
fun) SDoc -> SDoc -> SDoc
<> String -> SDoc
text String
", namely"])
       Arity
2 (SDoc -> SDoc
quotes (arg -> SDoc
forall a. Outputable a => a -> SDoc
ppr arg
arg))

-- | Add a "In the data declaration for T" or some such.
addTyConFlavCtxt :: Name -> TyConFlavour -> TcM a -> TcM a
addTyConFlavCtxt :: forall a. Name -> TyConFlavour -> TcM a -> TcM a
addTyConFlavCtxt Name
name TyConFlavour
flav
  = SDoc -> TcM a -> TcM a
forall a. SDoc -> TcM a -> TcM a
addErrCtxt (SDoc -> TcM a -> TcM a) -> SDoc -> TcM a -> TcM a
forall a b. (a -> b) -> a -> b
$ [SDoc] -> SDoc
hsep [ String -> SDoc
text String
"In the", TyConFlavour -> SDoc
forall a. Outputable a => a -> SDoc
ppr TyConFlavour
flav
                      , String -> SDoc
text String
"declaration for", SDoc -> SDoc
quotes (Name -> SDoc
forall a. Outputable a => a -> SDoc
ppr Name
name) ]