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

\section[TcType]{Types used in the typechecker}

This module provides the Type interface for front-end parts of the
compiler.  These parts

        * treat "source types" as opaque:
                newtypes, and predicates are meaningful.
        * look through usage types

The "tc" prefix is for "TypeChecker", because the type checker
is the principal client.
-}

{-# LANGUAGE CPP, ScopedTypeVariables, MultiWayIf, FlexibleContexts #-}

module TcType (
  --------------------------------
  -- Types
  TcType, TcSigmaType, TcRhoType, TcTauType, TcPredType, TcThetaType,
  TcTyVar, TcTyVarSet, TcDTyVarSet, TcTyCoVarSet, TcDTyCoVarSet,
  TcKind, TcCoVar, TcTyCoVar, TcTyVarBinder, TcTyCon,
  KnotTied,

  ExpType(..), InferResult(..), ExpSigmaType, ExpRhoType, mkCheckExpType,

  SyntaxOpType(..), synKnownType, mkSynFunTys,

  -- TcLevel
  TcLevel(..), topTcLevel, pushTcLevel, isTopTcLevel,
  strictlyDeeperThan, sameDepthAs,
  tcTypeLevel, tcTyVarLevel, maxTcLevel,
  promoteSkolem, promoteSkolemX, promoteSkolemsX,
  --------------------------------
  -- MetaDetails
  TcTyVarDetails(..), pprTcTyVarDetails, vanillaSkolemTv, superSkolemTv,
  MetaDetails(Flexi, Indirect), MetaInfo(..),
  isImmutableTyVar, isSkolemTyVar, isMetaTyVar,  isMetaTyVarTy, isTyVarTy,
  tcIsTcTyVar, isTyVarTyVar, isOverlappableTyVar,  isTyConableTyVar,
  isFskTyVar, isFmvTyVar, isFlattenTyVar,
  isAmbiguousTyVar, metaTyVarRef, metaTyVarInfo,
  isFlexi, isIndirect, isRuntimeUnkSkol,
  metaTyVarTcLevel, setMetaTyVarTcLevel, metaTyVarTcLevel_maybe,
  isTouchableMetaTyVar,
  isFloatedTouchableMetaTyVar,
  findDupTyVarTvs, mkTyVarNamePairs,

  --------------------------------
  -- Builders
  mkPhiTy, mkInfSigmaTy, mkSpecSigmaTy, mkSigmaTy,
  mkTcAppTy, mkTcAppTys, mkTcCastTy,

  --------------------------------
  -- Splitters
  -- These are important because they do not look through newtypes
  getTyVar,
  tcSplitForAllTy_maybe,
  tcSplitForAllTys, tcSplitForAllTysSameVis,
  tcSplitPiTys, tcSplitPiTy_maybe, tcSplitForAllVarBndrs,
  tcSplitPhiTy, tcSplitPredFunTy_maybe,
  tcSplitFunTy_maybe, tcSplitFunTys, tcFunArgTy, tcFunResultTy, tcFunResultTyN,
  tcSplitFunTysN,
  tcSplitTyConApp, tcSplitTyConApp_maybe,
  tcTyConAppTyCon, tcTyConAppTyCon_maybe, tcTyConAppArgs,
  tcSplitAppTy_maybe, tcSplitAppTy, tcSplitAppTys, tcRepSplitAppTy_maybe,
  tcRepGetNumAppTys,
  tcGetCastedTyVar_maybe, tcGetTyVar_maybe, tcGetTyVar, nextRole,
  tcSplitSigmaTy, tcSplitNestedSigmaTys, tcDeepSplitSigmaTy_maybe,

  ---------------------------------
  -- Predicates.
  -- Again, newtypes are opaque
  eqType, eqTypes, nonDetCmpType, nonDetCmpTypes, eqTypeX,
  pickyEqType, tcEqType, tcEqKind, tcEqTypeNoKindCheck, tcEqTypeVis,
  isSigmaTy, isRhoTy, isRhoExpTy, isOverloadedTy,
  isFloatingTy, isDoubleTy, isFloatTy, isIntTy, isWordTy, isStringTy,
  isIntegerTy, isBoolTy, isUnitTy, isCharTy, isCallStackTy, isCallStackPred,
  hasIPPred, isTauTy, isTauTyCon, tcIsTyVarTy, tcIsForAllTy,
  isPredTy, isTyVarClassPred, isTyVarHead, isInsolubleOccursCheck,
  checkValidClsArgs, hasTyVarHead,
  isRigidTy, isAlmostFunctionFree,

  ---------------------------------
  -- Misc type manipulators

  deNoteType,
  orphNamesOfType, orphNamesOfCo,
  orphNamesOfTypes, orphNamesOfCoCon,
  getDFunTyKey, evVarPred,

  ---------------------------------
  -- Predicate types
  mkMinimalBySCs, transSuperClasses,
  pickQuantifiablePreds, pickCapturedPreds,
  immSuperClasses, boxEqPred,
  isImprovementPred,

  -- * Finding type instances
  tcTyFamInsts, tcTyFamInstsAndVis, tcTyConAppTyFamInstsAndVis, isTyFamFree,

  -- * Finding "exact" (non-dead) type variables
  exactTyCoVarsOfType, exactTyCoVarsOfTypes,
  anyRewritableTyVar,

  ---------------------------------
  -- Foreign import and export
  isFFIArgumentTy,     -- :: DynFlags -> Safety -> Type -> Bool
  isFFIImportResultTy, -- :: DynFlags -> Type -> Bool
  isFFIExportResultTy, -- :: Type -> Bool
  isFFIExternalTy,     -- :: Type -> Bool
  isFFIDynTy,          -- :: Type -> Type -> Bool
  isFFIPrimArgumentTy, -- :: DynFlags -> Type -> Bool
  isFFIPrimResultTy,   -- :: DynFlags -> Type -> Bool
  isFFILabelTy,        -- :: Type -> Bool
  isFFITy,             -- :: Type -> Bool
  isFunPtrTy,          -- :: Type -> Bool
  tcSplitIOType_maybe, -- :: Type -> Maybe Type

  --------------------------------
  -- Rexported from Kind
  Kind, tcTypeKind,
  liftedTypeKind,
  constraintKind,
  isLiftedTypeKind, isUnliftedTypeKind, classifiesTypeWithValues,

  --------------------------------
  -- Rexported from Type
  Type, PredType, ThetaType, TyCoBinder,
  ArgFlag(..), AnonArgFlag(..), ForallVisFlag(..),

  mkForAllTy, mkForAllTys, mkTyCoInvForAllTys, mkSpecForAllTys, mkTyCoInvForAllTy,
  mkInvForAllTy, mkInvForAllTys,
  mkVisFunTy, mkVisFunTys, mkInvisFunTy, mkInvisFunTys,
  mkTyConApp, mkAppTy, mkAppTys,
  mkTyConTy, mkTyVarTy, mkTyVarTys,
  mkTyCoVarTy, mkTyCoVarTys,

  isClassPred, isEqPrimPred, isIPPred, isEqPred, isEqPredClass,
  mkClassPred,
  tcSplitDFunTy, tcSplitDFunHead, tcSplitMethodTy,
  isRuntimeRepVar, isKindLevPoly,
  isVisibleBinder, isInvisibleBinder,

  -- Type substitutions
  TCvSubst(..),         -- Representation visible to a few friends
  TvSubstEnv, emptyTCvSubst, mkEmptyTCvSubst,
  zipTvSubst,
  mkTvSubstPrs, notElemTCvSubst, unionTCvSubst,
  getTvSubstEnv, setTvSubstEnv, getTCvInScope, extendTCvInScope,
  extendTCvInScopeList, extendTCvInScopeSet, extendTvSubstAndInScope,
  Type.lookupTyVar, Type.extendTCvSubst, Type.substTyVarBndr,
  Type.extendTvSubst,
  isInScope, mkTCvSubst, mkTvSubst, zipTyEnv, zipCoEnv,
  Type.substTy, substTys, substTyWith, substTyWithCoVars,
  substTyAddInScope,
  substTyUnchecked, substTysUnchecked, substThetaUnchecked,
  substTyWithUnchecked,
  substCoUnchecked, substCoWithUnchecked,
  substTheta,

  isUnliftedType,       -- Source types are always lifted
  isUnboxedTupleType,   -- Ditto
  isPrimitiveType,

  tcView, coreView,

  tyCoVarsOfType, tyCoVarsOfTypes, closeOverKinds,
  tyCoFVsOfType, tyCoFVsOfTypes,
  tyCoVarsOfTypeDSet, tyCoVarsOfTypesDSet, closeOverKindsDSet,
  tyCoVarsOfTypeList, tyCoVarsOfTypesList,
  noFreeVarsOfType,

  --------------------------------
  pprKind, pprParendKind, pprSigmaType,
  pprType, pprParendType, pprTypeApp, pprTyThingCategory, tyThingCategory,
  pprTheta, pprParendTheta, pprThetaArrowTy, pprClassPred,
  pprTCvBndr, pprTCvBndrs,

  TypeSize, sizeType, sizeTypes, scopedSort,

  ---------------------------------
  -- argument visibility
  tcTyConVisibilities, isNextTyConArgVisible, isNextArgVisible

  ) where

#include "HsVersions.h"

-- friends:
import GhcPrelude

import TyCoRep
import TyCoSubst ( mkTvSubst, substTyWithCoVars )
import TyCoFVs
import TyCoPpr
import Class
import Var
import ForeignCall
import VarSet
import Coercion
import Type
import Predicate
import RepType
import TyCon

-- others:
import DynFlags
import CoreFVs
import Name -- hiding (varName)
            -- We use this to make dictionaries for type literals.
            -- Perhaps there's a better way to do this?
import NameSet
import VarEnv
import PrelNames
import TysWiredIn( coercibleClass, eqClass, heqClass, unitTyCon, unitTyConKey
                 , listTyCon, constraintKind )
import BasicTypes
import Util
import Maybes
import ListSetOps ( getNth, findDupsEq )
import Outputable
import FastString
import ErrUtils( Validity(..), MsgDoc, isValid )
import qualified GHC.LanguageExtensions as LangExt

import Data.List  ( mapAccumL )
-- import Data.Functor.Identity( Identity(..) )
import Data.IORef
import Data.List.NonEmpty( NonEmpty(..) )

{-
************************************************************************
*                                                                      *
              Types
*                                                                      *
************************************************************************

The type checker divides the generic Type world into the
following more structured beasts:

sigma ::= forall tyvars. phi
        -- A sigma type is a qualified type
        --
        -- Note that even if 'tyvars' is empty, theta
        -- may not be: e.g.   (?x::Int) => Int

        -- Note that 'sigma' is in prenex form:
        -- all the foralls are at the front.
        -- A 'phi' type has no foralls to the right of
        -- an arrow

phi :: theta => rho

rho ::= sigma -> rho
     |  tau

-- A 'tau' type has no quantification anywhere
-- Note that the args of a type constructor must be taus
tau ::= tyvar
     |  tycon tau_1 .. tau_n
     |  tau_1 tau_2
     |  tau_1 -> tau_2

-- In all cases, a (saturated) type synonym application is legal,
-- provided it expands to the required form.

Note [TcTyVars and TyVars in the typechecker]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
The typechecker uses a lot of type variables with special properties,
notably being a unification variable with a mutable reference.  These
use the 'TcTyVar' variant of Var.Var.

Note, though, that a /bound/ type variable can (and probably should)
be a TyVar.  E.g
    forall a. a -> a
Here 'a' is really just a deBruijn-number; it certainly does not have
a signficant TcLevel (as every TcTyVar does).  So a forall-bound type
variable should be TyVars; and hence a TyVar can appear free in a TcType.

The type checker and constraint solver can also encounter /free/ type
variables that use the 'TyVar' variant of Var.Var, for a couple of
reasons:

  - When typechecking a class decl, say
       class C (a :: k) where
          foo :: T a -> Int
    We have first kind-check the header; fix k and (a:k) to be
    TyVars, bring 'k' and 'a' into scope, and kind check the
    signature for 'foo'.  In doing so we call solveEqualities to
    solve any kind equalities in foo's signature.  So the solver
    may see free occurrences of 'k'.

    See calls to tcExtendTyVarEnv for other places that ordinary
    TyVars are bought into scope, and hence may show up in the types
    and kinds generated by TcHsType.

  - The pattern-match overlap checker calls the constraint solver,
    long afer TcTyVars have been zonked away

It's convenient to simply treat these TyVars as skolem constants,
which of course they are.  We give them a level number of "outermost",
so they behave as global constants.  Specifically:

* Var.tcTyVarDetails succeeds on a TyVar, returning
  vanillaSkolemTv, as well as on a TcTyVar.

* tcIsTcTyVar returns True for both TyVar and TcTyVar variants
  of Var.Var.  The "tc" prefix means "a type variable that can be
  encountered by the typechecker".

This is a bit of a change from an earlier era when we remoselessly
insisted on real TcTyVars in the type checker.  But that seems
unnecessary (for skolems, TyVars are fine) and it's now very hard
to guarantee, with the advent of kind equalities.

Note [Coercion variables in free variable lists]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
There are several places in the GHC codebase where functions like
tyCoVarsOfType, tyCoVarsOfCt, et al. are used to compute the free type
variables of a type. The "Co" part of these functions' names shouldn't be
dismissed, as it is entirely possible that they will include coercion variables
in addition to type variables! As a result, there are some places in TcType
where we must take care to check that a variable is a _type_ variable (using
isTyVar) before calling tcTyVarDetails--a partial function that is not defined
for coercion variables--on the variable. Failing to do so led to
GHC #12785.
-}

-- See Note [TcTyVars and TyVars in the typechecker]
type TcCoVar = CoVar    -- Used only during type inference
type TcType = Type      -- A TcType can have mutable type variables
type TcTyCoVar = Var    -- Either a TcTyVar or a CoVar
        -- Invariant on ForAllTy in TcTypes:
        --      forall a. T
        -- a cannot occur inside a MutTyVar in T; that is,
        -- T is "flattened" before quantifying over a

type TcTyVarBinder   = TyVarBinder
type TcTyCon         = TyCon   -- these can be the TcTyCon constructor

-- These types do not have boxy type variables in them
type TcPredType     = PredType
type TcThetaType    = ThetaType
type TcSigmaType    = TcType
type TcRhoType      = TcType  -- Note [TcRhoType]
type TcTauType      = TcType
type TcKind         = Kind
type TcTyVarSet     = TyVarSet
type TcTyCoVarSet   = TyCoVarSet
type TcDTyVarSet    = DTyVarSet
type TcDTyCoVarSet  = DTyCoVarSet

{- *********************************************************************
*                                                                      *
          ExpType: an "expected type" in the type checker
*                                                                      *
********************************************************************* -}

-- | An expected type to check against during type-checking.
-- See Note [ExpType] in TcMType, where you'll also find manipulators.
data ExpType = Check TcType
             | Infer !InferResult

data InferResult
  = IR { InferResult -> Unique
ir_uniq :: Unique  -- For debugging only

       , InferResult -> TcLevel
ir_lvl  :: TcLevel -- See Note [TcLevel of ExpType] in TcMType

       , InferResult -> Bool
ir_inst :: Bool
         -- True <=> deeply instantiate before returning
         --           i.e. return a RhoType
         -- False <=> do not instantiate before returning
         --           i.e. return a SigmaType
         -- See Note [Deep instantiation of InferResult] in TcUnify

       , InferResult -> IORef (Maybe TcType)
ir_ref  :: IORef (Maybe TcType) }
         -- The type that fills in this hole should be a Type,
         -- that is, its kind should be (TYPE rr) for some rr

type ExpSigmaType = ExpType
type ExpRhoType   = ExpType

instance Outputable ExpType where
  ppr :: ExpType -> SDoc
ppr (Check TcType
ty) = String -> SDoc
text String
"Check" SDoc -> SDoc -> SDoc
<> SDoc -> SDoc
braces (TcType -> SDoc
forall a. Outputable a => a -> SDoc
ppr TcType
ty)
  ppr (Infer InferResult
ir) = InferResult -> SDoc
forall a. Outputable a => a -> SDoc
ppr InferResult
ir

instance Outputable InferResult where
  ppr :: InferResult -> SDoc
ppr (IR { ir_uniq :: InferResult -> Unique
ir_uniq = Unique
u, ir_lvl :: InferResult -> TcLevel
ir_lvl = TcLevel
lvl
          , ir_inst :: InferResult -> Bool
ir_inst = Bool
inst })
    = String -> SDoc
text String
"Infer" SDoc -> SDoc -> SDoc
<> SDoc -> SDoc
braces (Unique -> SDoc
forall a. Outputable a => a -> SDoc
ppr Unique
u SDoc -> SDoc -> SDoc
<> SDoc
comma SDoc -> SDoc -> SDoc
<> TcLevel -> SDoc
forall a. Outputable a => a -> SDoc
ppr TcLevel
lvl SDoc -> SDoc -> SDoc
<+> Bool -> SDoc
forall a. Outputable a => a -> SDoc
ppr Bool
inst)

-- | Make an 'ExpType' suitable for checking.
mkCheckExpType :: TcType -> ExpType
mkCheckExpType :: TcType -> ExpType
mkCheckExpType = TcType -> ExpType
Check


{- *********************************************************************
*                                                                      *
          SyntaxOpType
*                                                                      *
********************************************************************* -}

-- | What to expect for an argument to a rebindable-syntax operator.
-- Quite like 'Type', but allows for holes to be filled in by tcSyntaxOp.
-- The callback called from tcSyntaxOp gets a list of types; the meaning
-- of these types is determined by a left-to-right depth-first traversal
-- of the 'SyntaxOpType' tree. So if you pass in
--
-- > SynAny `SynFun` (SynList `SynFun` SynType Int) `SynFun` SynAny
--
-- you'll get three types back: one for the first 'SynAny', the /element/
-- type of the list, and one for the last 'SynAny'. You don't get anything
-- for the 'SynType', because you've said positively that it should be an
-- Int, and so it shall be.
--
-- This is defined here to avoid defining it in TcExpr.hs-boot.
data SyntaxOpType
  = SynAny     -- ^ Any type
  | SynRho     -- ^ A rho type, deeply skolemised or instantiated as appropriate
  | SynList    -- ^ A list type. You get back the element type of the list
  | SynFun SyntaxOpType SyntaxOpType
               -- ^ A function.
  | SynType ExpType   -- ^ A known type.
infixr 0 `SynFun`

-- | Like 'SynType' but accepts a regular TcType
synKnownType :: TcType -> SyntaxOpType
synKnownType :: TcType -> SyntaxOpType
synKnownType = ExpType -> SyntaxOpType
SynType (ExpType -> SyntaxOpType)
-> (TcType -> ExpType) -> TcType -> SyntaxOpType
forall b c a. (b -> c) -> (a -> b) -> a -> c
. TcType -> ExpType
mkCheckExpType

-- | Like 'mkFunTys' but for 'SyntaxOpType'
mkSynFunTys :: [SyntaxOpType] -> ExpType -> SyntaxOpType
mkSynFunTys :: [SyntaxOpType] -> ExpType -> SyntaxOpType
mkSynFunTys [SyntaxOpType]
arg_tys ExpType
res_ty = (SyntaxOpType -> SyntaxOpType -> SyntaxOpType)
-> SyntaxOpType -> [SyntaxOpType] -> SyntaxOpType
forall (t :: * -> *) a b.
Foldable t =>
(a -> b -> b) -> b -> t a -> b
foldr SyntaxOpType -> SyntaxOpType -> SyntaxOpType
SynFun (ExpType -> SyntaxOpType
SynType ExpType
res_ty) [SyntaxOpType]
arg_tys


{-
Note [TcRhoType]
~~~~~~~~~~~~~~~~
A TcRhoType has no foralls or contexts at the top, or to the right of an arrow
  YES    (forall a. a->a) -> Int
  NO     forall a. a ->  Int
  NO     Eq a => a -> a
  NO     Int -> forall a. a -> Int


************************************************************************
*                                                                      *
        TyVarDetails, MetaDetails, MetaInfo
*                                                                      *
************************************************************************

TyVarDetails gives extra info about type variables, used during type
checking.  It's attached to mutable type variables only.
It's knot-tied back to Var.hs.  There is no reason in principle
why Var.hs shouldn't actually have the definition, but it "belongs" here.

Note [Signature skolems]
~~~~~~~~~~~~~~~~~~~~~~~~
A TyVarTv is a specialised variant of TauTv, with the following invarints:

    * A TyVarTv can be unified only with a TyVar,
      not with any other type

    * Its MetaDetails, if filled in, will always be another TyVarTv
      or a SkolemTv

TyVarTvs are only distinguished to improve error messages.
Consider this

  data T (a:k1) = MkT (S a)
  data S (b:k2) = MkS (T b)

When doing kind inference on {S,T} we don't want *skolems* for k1,k2,
because they end up unifying; we want those TyVarTvs again.


Note [TyVars and TcTyVars during type checking]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
The Var type has constructors TyVar and TcTyVar.  They are used
as follows:

* TcTyVar: used /only/ during type checking.  Should never appear
  afterwards.  May contain a mutable field, in the MetaTv case.

* TyVar: is never seen by the constraint solver, except locally
  inside a type like (forall a. [a] ->[a]), where 'a' is a TyVar.
  We instantiate these with TcTyVars before exposing the type
  to the constraint solver.

I have swithered about the latter invariant, excluding TyVars from the
constraint solver.  It's not strictly essential, and indeed
(historically but still there) Var.tcTyVarDetails returns
vanillaSkolemTv for a TyVar.

But ultimately I want to seeparate Type from TcType, and in that case
we would need to enforce the separation.
-}

-- A TyVarDetails is inside a TyVar
-- See Note [TyVars and TcTyVars]
data TcTyVarDetails
  = SkolemTv      -- A skolem
       TcLevel    -- Level of the implication that binds it
                  -- See TcUnify Note [Deeper level on the left] for
                  --     how this level number is used
       Bool       -- True <=> this skolem type variable can be overlapped
                  --          when looking up instances
                  -- See Note [Binding when looking up instances] in InstEnv

  | RuntimeUnk    -- Stands for an as-yet-unknown type in the GHCi
                  -- interactive context

  | MetaTv { TcTyVarDetails -> MetaInfo
mtv_info  :: MetaInfo
           , TcTyVarDetails -> IORef MetaDetails
mtv_ref   :: IORef MetaDetails
           , TcTyVarDetails -> TcLevel
mtv_tclvl :: TcLevel }  -- See Note [TcLevel and untouchable type variables]

vanillaSkolemTv, superSkolemTv :: TcTyVarDetails
-- See Note [Binding when looking up instances] in InstEnv
vanillaSkolemTv :: TcTyVarDetails
vanillaSkolemTv = TcLevel -> Bool -> TcTyVarDetails
SkolemTv TcLevel
topTcLevel Bool
False  -- Might be instantiated
superSkolemTv :: TcTyVarDetails
superSkolemTv   = TcLevel -> Bool -> TcTyVarDetails
SkolemTv TcLevel
topTcLevel Bool
True   -- Treat this as a completely distinct type
                  -- The choice of level number here is a bit dodgy, but
                  -- topTcLevel works in the places that vanillaSkolemTv is used

instance Outputable TcTyVarDetails where
  ppr :: TcTyVarDetails -> SDoc
ppr = TcTyVarDetails -> SDoc
pprTcTyVarDetails

pprTcTyVarDetails :: TcTyVarDetails -> SDoc
-- For debugging
pprTcTyVarDetails :: TcTyVarDetails -> SDoc
pprTcTyVarDetails (RuntimeUnk {})      = String -> SDoc
text String
"rt"
pprTcTyVarDetails (SkolemTv TcLevel
lvl Bool
True)  = String -> SDoc
text String
"ssk" SDoc -> SDoc -> SDoc
<> SDoc
colon SDoc -> SDoc -> SDoc
<> TcLevel -> SDoc
forall a. Outputable a => a -> SDoc
ppr TcLevel
lvl
pprTcTyVarDetails (SkolemTv TcLevel
lvl Bool
False) = String -> SDoc
text String
"sk"  SDoc -> SDoc -> SDoc
<> SDoc
colon SDoc -> SDoc -> SDoc
<> TcLevel -> SDoc
forall a. Outputable a => a -> SDoc
ppr TcLevel
lvl
pprTcTyVarDetails (MetaTv { mtv_info :: TcTyVarDetails -> MetaInfo
mtv_info = MetaInfo
info, mtv_tclvl :: TcTyVarDetails -> TcLevel
mtv_tclvl = TcLevel
tclvl })
  = MetaInfo -> SDoc
forall a. Outputable a => a -> SDoc
ppr MetaInfo
info SDoc -> SDoc -> SDoc
<> SDoc
colon SDoc -> SDoc -> SDoc
<> TcLevel -> SDoc
forall a. Outputable a => a -> SDoc
ppr TcLevel
tclvl

-----------------------------
data MetaDetails
  = Flexi  -- Flexi type variables unify to become Indirects
  | Indirect TcType

data MetaInfo
   = TauTv         -- This MetaTv is an ordinary unification variable
                   -- A TauTv is always filled in with a tau-type, which
                   -- never contains any ForAlls.

   | TyVarTv       -- A variant of TauTv, except that it should not be
                   --   unified with a type, only with a type variable
                   -- See Note [Signature skolems]

   | FlatMetaTv    -- A flatten meta-tyvar
                   -- It is a meta-tyvar, but it is always untouchable, with level 0
                   -- See Note [The flattening story] in TcFlatten

   | FlatSkolTv    -- A flatten skolem tyvar
                   -- Just like FlatMetaTv, but is comletely "owned" by
                   --   its Given CFunEqCan.
                   -- It is filled in /only/ by unflattenGivens
                   -- See Note [The flattening story] in TcFlatten

instance Outputable MetaDetails where
  ppr :: MetaDetails -> SDoc
ppr MetaDetails
Flexi         = String -> SDoc
text String
"Flexi"
  ppr (Indirect TcType
ty) = String -> SDoc
text String
"Indirect" SDoc -> SDoc -> SDoc
<+> TcType -> SDoc
forall a. Outputable a => a -> SDoc
ppr TcType
ty

instance Outputable MetaInfo where
  ppr :: MetaInfo -> SDoc
ppr MetaInfo
TauTv         = String -> SDoc
text String
"tau"
  ppr MetaInfo
TyVarTv       = String -> SDoc
text String
"tyv"
  ppr MetaInfo
FlatMetaTv    = String -> SDoc
text String
"fmv"
  ppr MetaInfo
FlatSkolTv    = String -> SDoc
text String
"fsk"

{- *********************************************************************
*                                                                      *
                Untouchable type variables
*                                                                      *
********************************************************************* -}

newtype TcLevel = TcLevel Int deriving( TcLevel -> TcLevel -> Bool
(TcLevel -> TcLevel -> Bool)
-> (TcLevel -> TcLevel -> Bool) -> Eq TcLevel
forall a. (a -> a -> Bool) -> (a -> a -> Bool) -> Eq a
/= :: TcLevel -> TcLevel -> Bool
$c/= :: TcLevel -> TcLevel -> Bool
== :: TcLevel -> TcLevel -> Bool
$c== :: TcLevel -> TcLevel -> Bool
Eq, Eq TcLevel
Eq TcLevel
-> (TcLevel -> TcLevel -> Ordering)
-> (TcLevel -> TcLevel -> Bool)
-> (TcLevel -> TcLevel -> Bool)
-> (TcLevel -> TcLevel -> Bool)
-> (TcLevel -> TcLevel -> Bool)
-> (TcLevel -> TcLevel -> TcLevel)
-> (TcLevel -> TcLevel -> TcLevel)
-> Ord TcLevel
TcLevel -> TcLevel -> Bool
TcLevel -> TcLevel -> Ordering
TcLevel -> TcLevel -> TcLevel
forall a.
Eq a
-> (a -> a -> Ordering)
-> (a -> a -> Bool)
-> (a -> a -> Bool)
-> (a -> a -> Bool)
-> (a -> a -> Bool)
-> (a -> a -> a)
-> (a -> a -> a)
-> Ord a
min :: TcLevel -> TcLevel -> TcLevel
$cmin :: TcLevel -> TcLevel -> TcLevel
max :: TcLevel -> TcLevel -> TcLevel
$cmax :: TcLevel -> TcLevel -> TcLevel
>= :: TcLevel -> TcLevel -> Bool
$c>= :: TcLevel -> TcLevel -> Bool
> :: TcLevel -> TcLevel -> Bool
$c> :: TcLevel -> TcLevel -> Bool
<= :: TcLevel -> TcLevel -> Bool
$c<= :: TcLevel -> TcLevel -> Bool
< :: TcLevel -> TcLevel -> Bool
$c< :: TcLevel -> TcLevel -> Bool
compare :: TcLevel -> TcLevel -> Ordering
$ccompare :: TcLevel -> TcLevel -> Ordering
$cp1Ord :: Eq TcLevel
Ord )
  -- See Note [TcLevel and untouchable type variables] for what this Int is
  -- See also Note [TcLevel assignment]

{-
Note [TcLevel and untouchable type variables]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
* Each unification variable (MetaTv)
  and each Implication
  has a level number (of type TcLevel)

* INVARIANTS.  In a tree of Implications,

    (ImplicInv) The level number (ic_tclvl) of an Implication is
                STRICTLY GREATER THAN that of its parent

    (SkolInv)   The level number of the skolems (ic_skols) of an
                Implication is equal to the level of the implication
                itself (ic_tclvl)

    (GivenInv)  The level number of a unification variable appearing
                in the 'ic_given' of an implication I should be
                STRICTLY LESS THAN the ic_tclvl of I

    (WantedInv) The level number of a unification variable appearing
                in the 'ic_wanted' of an implication I should be
                LESS THAN OR EQUAL TO the ic_tclvl of I
                See Note [WantedInv]

* A unification variable is *touchable* if its level number
  is EQUAL TO that of its immediate parent implication,
  and it is a TauTv or TyVarTv (but /not/ FlatMetaTv or FlatSkolTv)

Note [WantedInv]
~~~~~~~~~~~~~~~~
Why is WantedInv important?  Consider this implication, where
the constraint (C alpha[3]) disobeys WantedInv:

   forall[2] a. blah => (C alpha[3])
                        (forall[3] b. alpha[3] ~ b)

We can unify alpha:=b in the inner implication, because 'alpha' is
touchable; but then 'b' has excaped its scope into the outer implication.

Note [Skolem escape prevention]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
We only unify touchable unification variables.  Because of
(WantedInv), there can be no occurrences of the variable further out,
so the unification can't cause the skolems to escape. Example:
     data T = forall a. MkT a (a->Int)
     f x (MkT v f) = length [v,x]
We decide (x::alpha), and generate an implication like
      [1]forall a. (a ~ alpha[0])
But we must not unify alpha:=a, because the skolem would escape.

For the cases where we DO want to unify, we rely on floating the
equality.   Example (with same T)
     g x (MkT v f) = x && True
We decide (x::alpha), and generate an implication like
      [1]forall a. (Bool ~ alpha[0])
We do NOT unify directly, bur rather float out (if the constraint
does not mention 'a') to get
      (Bool ~ alpha[0]) /\ [1]forall a.()
and NOW we can unify alpha.

The same idea of only unifying touchables solves another problem.
Suppose we had
   (F Int ~ uf[0])  /\  [1](forall a. C a => F Int ~ beta[1])
In this example, beta is touchable inside the implication. The
first solveSimpleWanteds step leaves 'uf' un-unified. Then we move inside
the implication where a new constraint
       uf  ~  beta
emerges. If we (wrongly) spontaneously solved it to get uf := beta,
the whole implication disappears but when we pop out again we are left with
(F Int ~ uf) which will be unified by our final zonking stage and
uf will get unified *once more* to (F Int).

Note [TcLevel assignment]
~~~~~~~~~~~~~~~~~~~~~~~~~
We arrange the TcLevels like this

   0   Top level
   1   First-level implication constraints
   2   Second-level implication constraints
   ...etc...
-}

maxTcLevel :: TcLevel -> TcLevel -> TcLevel
maxTcLevel :: TcLevel -> TcLevel -> TcLevel
maxTcLevel (TcLevel Int
a) (TcLevel Int
b) = Int -> TcLevel
TcLevel (Int
a Int -> Int -> Int
forall a. Ord a => a -> a -> a
`max` Int
b)

topTcLevel :: TcLevel
-- See Note [TcLevel assignment]
topTcLevel :: TcLevel
topTcLevel = Int -> TcLevel
TcLevel Int
0   -- 0 = outermost level

isTopTcLevel :: TcLevel -> Bool
isTopTcLevel :: TcLevel -> Bool
isTopTcLevel (TcLevel Int
0) = Bool
True
isTopTcLevel TcLevel
_           = Bool
False

pushTcLevel :: TcLevel -> TcLevel
-- See Note [TcLevel assignment]
pushTcLevel :: TcLevel -> TcLevel
pushTcLevel (TcLevel Int
us) = Int -> TcLevel
TcLevel (Int
us Int -> Int -> Int
forall a. Num a => a -> a -> a
+ Int
1)

strictlyDeeperThan :: TcLevel -> TcLevel -> Bool
strictlyDeeperThan :: TcLevel -> TcLevel -> Bool
strictlyDeeperThan (TcLevel Int
tv_tclvl) (TcLevel Int
ctxt_tclvl)
  = Int
tv_tclvl Int -> Int -> Bool
forall a. Ord a => a -> a -> Bool
> Int
ctxt_tclvl

sameDepthAs :: TcLevel -> TcLevel -> Bool
sameDepthAs :: TcLevel -> TcLevel -> Bool
sameDepthAs (TcLevel Int
ctxt_tclvl) (TcLevel Int
tv_tclvl)
  = Int
ctxt_tclvl Int -> Int -> Bool
forall a. Eq a => a -> a -> Bool
== Int
tv_tclvl   -- NB: invariant ctxt_tclvl >= tv_tclvl
                             --     So <= would be equivalent

checkTcLevelInvariant :: TcLevel -> TcLevel -> Bool
-- Checks (WantedInv) from Note [TcLevel and untouchable type variables]
checkTcLevelInvariant :: TcLevel -> TcLevel -> Bool
checkTcLevelInvariant (TcLevel Int
ctxt_tclvl) (TcLevel Int
tv_tclvl)
  = Int
ctxt_tclvl Int -> Int -> Bool
forall a. Ord a => a -> a -> Bool
>= Int
tv_tclvl

-- Returns topTcLevel for non-TcTyVars
tcTyVarLevel :: TcTyVar -> TcLevel
tcTyVarLevel :: TcTyVar -> TcLevel
tcTyVarLevel TcTyVar
tv
  = case TcTyVar -> TcTyVarDetails
tcTyVarDetails TcTyVar
tv of
          MetaTv { mtv_tclvl :: TcTyVarDetails -> TcLevel
mtv_tclvl = TcLevel
tv_lvl } -> TcLevel
tv_lvl
          SkolemTv TcLevel
tv_lvl Bool
_             -> TcLevel
tv_lvl
          TcTyVarDetails
RuntimeUnk                    -> TcLevel
topTcLevel


tcTypeLevel :: TcType -> TcLevel
-- Max level of any free var of the type
tcTypeLevel :: TcType -> TcLevel
tcTypeLevel TcType
ty
  = (TcTyVar -> TcLevel -> TcLevel) -> TcLevel -> DVarSet -> TcLevel
forall a. (TcTyVar -> a -> a) -> a -> DVarSet -> a
foldDVarSet TcTyVar -> TcLevel -> TcLevel
add TcLevel
topTcLevel (TcType -> DVarSet
tyCoVarsOfTypeDSet TcType
ty)
  where
    add :: TcTyVar -> TcLevel -> TcLevel
add TcTyVar
v TcLevel
lvl
      | TcTyVar -> Bool
isTcTyVar TcTyVar
v = TcLevel
lvl TcLevel -> TcLevel -> TcLevel
`maxTcLevel` TcTyVar -> TcLevel
tcTyVarLevel TcTyVar
v
      | Bool
otherwise = TcLevel
lvl

instance Outputable TcLevel where
  ppr :: TcLevel -> SDoc
ppr (TcLevel Int
us) = Int -> SDoc
forall a. Outputable a => a -> SDoc
ppr Int
us

promoteSkolem :: TcLevel -> TcTyVar -> TcTyVar
promoteSkolem :: TcLevel -> TcTyVar -> TcTyVar
promoteSkolem TcLevel
tclvl TcTyVar
skol
  | TcLevel
tclvl TcLevel -> TcLevel -> Bool
forall a. Ord a => a -> a -> Bool
< TcTyVar -> TcLevel
tcTyVarLevel TcTyVar
skol
  = ASSERT( isTcTyVar skol && isSkolemTyVar skol )
    TcTyVar -> TcTyVarDetails -> TcTyVar
setTcTyVarDetails TcTyVar
skol (TcLevel -> Bool -> TcTyVarDetails
SkolemTv TcLevel
tclvl (TcTyVar -> Bool
isOverlappableTyVar TcTyVar
skol))

  | Bool
otherwise
  = TcTyVar
skol

-- | Change the TcLevel in a skolem, extending a substitution
promoteSkolemX :: TcLevel -> TCvSubst -> TcTyVar -> (TCvSubst, TcTyVar)
promoteSkolemX :: TcLevel -> TCvSubst -> TcTyVar -> (TCvSubst, TcTyVar)
promoteSkolemX TcLevel
tclvl TCvSubst
subst TcTyVar
skol
  = ASSERT( isTcTyVar skol && isSkolemTyVar skol )
    (TCvSubst
new_subst, TcTyVar
new_skol)
  where
    new_skol :: TcTyVar
new_skol
      | TcLevel
tclvl TcLevel -> TcLevel -> Bool
forall a. Ord a => a -> a -> Bool
< TcTyVar -> TcLevel
tcTyVarLevel TcTyVar
skol
      = TcTyVar -> TcTyVarDetails -> TcTyVar
setTcTyVarDetails ((TcType -> TcType) -> TcTyVar -> TcTyVar
updateTyVarKind (HasCallStack => TCvSubst -> TcType -> TcType
TCvSubst -> TcType -> TcType
substTy TCvSubst
subst) TcTyVar
skol)
                          (TcLevel -> Bool -> TcTyVarDetails
SkolemTv TcLevel
tclvl (TcTyVar -> Bool
isOverlappableTyVar TcTyVar
skol))
      | Bool
otherwise
      = (TcType -> TcType) -> TcTyVar -> TcTyVar
updateTyVarKind (HasCallStack => TCvSubst -> TcType -> TcType
TCvSubst -> TcType -> TcType
substTy TCvSubst
subst) TcTyVar
skol
    new_subst :: TCvSubst
new_subst = TCvSubst -> TcTyVar -> TcTyVar -> TCvSubst
extendTvSubstWithClone TCvSubst
subst TcTyVar
skol TcTyVar
new_skol

promoteSkolemsX :: TcLevel -> TCvSubst -> [TcTyVar] -> (TCvSubst, [TcTyVar])
promoteSkolemsX :: TcLevel -> TCvSubst -> [TcTyVar] -> (TCvSubst, [TcTyVar])
promoteSkolemsX TcLevel
tclvl = (TCvSubst -> TcTyVar -> (TCvSubst, TcTyVar))
-> TCvSubst -> [TcTyVar] -> (TCvSubst, [TcTyVar])
forall (t :: * -> *) a b c.
Traversable t =>
(a -> b -> (a, c)) -> a -> t b -> (a, t c)
mapAccumL (TcLevel -> TCvSubst -> TcTyVar -> (TCvSubst, TcTyVar)
promoteSkolemX TcLevel
tclvl)

{- *********************************************************************
*                                                                      *
    Finding type family instances
*                                                                      *
************************************************************************
-}

-- | Finds outermost type-family applications occurring in a type,
-- after expanding synonyms.  In the list (F, tys) that is returned
-- we guarantee that tys matches F's arity.  For example, given
--    type family F a :: * -> *    (arity 1)
-- calling tcTyFamInsts on (Maybe (F Int Bool) will return
--     (F, [Int]), not (F, [Int,Bool])
--
-- This is important for its use in deciding termination of type
-- instances (see #11581).  E.g.
--    type instance G [Int] = ...(F Int <big type>)...
-- we don't need to take <big type> into account when asking if
-- the calls on the RHS are smaller than the LHS
tcTyFamInsts :: Type -> [(TyCon, [Type])]
tcTyFamInsts :: TcType -> [(TyCon, [TcType])]
tcTyFamInsts = ((Bool, TyCon, [TcType]) -> (TyCon, [TcType]))
-> [(Bool, TyCon, [TcType])] -> [(TyCon, [TcType])]
forall a b. (a -> b) -> [a] -> [b]
map (\(Bool
_,TyCon
b,[TcType]
c) -> (TyCon
b,[TcType]
c)) ([(Bool, TyCon, [TcType])] -> [(TyCon, [TcType])])
-> (TcType -> [(Bool, TyCon, [TcType])])
-> TcType
-> [(TyCon, [TcType])]
forall b c a. (b -> c) -> (a -> b) -> a -> c
. TcType -> [(Bool, TyCon, [TcType])]
tcTyFamInstsAndVis

-- | Like 'tcTyFamInsts', except that the output records whether the
-- type family and its arguments occur as an /invisible/ argument in
-- some type application. This information is useful because it helps GHC know
-- when to turn on @-fprint-explicit-kinds@ during error reporting so that
-- users can actually see the type family being mentioned.
--
-- As an example, consider:
--
-- @
-- class C a
-- data T (a :: k)
-- type family F a :: k
-- instance C (T @(F Int) (F Bool))
-- @
--
-- There are two occurrences of the type family `F` in that `C` instance, so
-- @'tcTyFamInstsAndVis' (C (T \@(F Int) (F Bool)))@ will return:
--
-- @
-- [ ('True',  F, [Int])
-- , ('False', F, [Bool]) ]
-- @
--
-- @F Int@ is paired with 'True' since it appears as an /invisible/ argument
-- to @C@, whereas @F Bool@ is paired with 'False' since it appears an a
-- /visible/ argument to @C@.
--
-- See also @Note [Kind arguments in error messages]@ in "TcErrors".
tcTyFamInstsAndVis :: Type -> [(Bool, TyCon, [Type])]
tcTyFamInstsAndVis :: TcType -> [(Bool, TyCon, [TcType])]
tcTyFamInstsAndVis = Bool -> TcType -> [(Bool, TyCon, [TcType])]
tcTyFamInstsAndVisX Bool
False

tcTyFamInstsAndVisX
  :: Bool -- ^ Is this an invisible argument to some type application?
  -> Type -> [(Bool, TyCon, [Type])]
tcTyFamInstsAndVisX :: Bool -> TcType -> [(Bool, TyCon, [TcType])]
tcTyFamInstsAndVisX = Bool -> TcType -> [(Bool, TyCon, [TcType])]
go
  where
    go :: Bool -> TcType -> [(Bool, TyCon, [TcType])]
go Bool
is_invis_arg TcType
ty
      | Just TcType
exp_ty <- TcType -> Maybe TcType
tcView TcType
ty       = Bool -> TcType -> [(Bool, TyCon, [TcType])]
go Bool
is_invis_arg TcType
exp_ty
    go Bool
_ (TyVarTy TcTyVar
_)                   = []
    go Bool
is_invis_arg (TyConApp TyCon
tc [TcType]
tys)
      | TyCon -> Bool
isTypeFamilyTyCon TyCon
tc
      = [(Bool
is_invis_arg, TyCon
tc, Int -> [TcType] -> [TcType]
forall a. Int -> [a] -> [a]
take (TyCon -> Int
tyConArity TyCon
tc) [TcType]
tys)]
      | Bool
otherwise
      = Bool -> TyCon -> [TcType] -> [(Bool, TyCon, [TcType])]
tcTyConAppTyFamInstsAndVisX Bool
is_invis_arg TyCon
tc [TcType]
tys
    go Bool
_            (LitTy {})         = []
    go Bool
is_invis_arg (ForAllTy TyCoVarBinder
bndr TcType
ty) = Bool -> TcType -> [(Bool, TyCon, [TcType])]
go Bool
is_invis_arg (TyCoVarBinder -> TcType
forall argf. VarBndr TcTyVar argf -> TcType
binderType TyCoVarBinder
bndr)
                                         [(Bool, TyCon, [TcType])]
-> [(Bool, TyCon, [TcType])] -> [(Bool, TyCon, [TcType])]
forall a. [a] -> [a] -> [a]
++ Bool -> TcType -> [(Bool, TyCon, [TcType])]
go Bool
is_invis_arg TcType
ty
    go Bool
is_invis_arg (FunTy AnonArgFlag
_ TcType
ty1 TcType
ty2)  = Bool -> TcType -> [(Bool, TyCon, [TcType])]
go Bool
is_invis_arg TcType
ty1
                                         [(Bool, TyCon, [TcType])]
-> [(Bool, TyCon, [TcType])] -> [(Bool, TyCon, [TcType])]
forall a. [a] -> [a] -> [a]
++ Bool -> TcType -> [(Bool, TyCon, [TcType])]
go Bool
is_invis_arg TcType
ty2
    go Bool
is_invis_arg ty :: TcType
ty@(AppTy TcType
_ TcType
_)     =
      let (TcType
ty_head, [TcType]
ty_args) = TcType -> (TcType, [TcType])
splitAppTys TcType
ty
          ty_arg_flags :: [ArgFlag]
ty_arg_flags       = TcType -> [TcType] -> [ArgFlag]
appTyArgFlags TcType
ty_head [TcType]
ty_args
      in Bool -> TcType -> [(Bool, TyCon, [TcType])]
go Bool
is_invis_arg TcType
ty_head
         [(Bool, TyCon, [TcType])]
-> [(Bool, TyCon, [TcType])] -> [(Bool, TyCon, [TcType])]
forall a. [a] -> [a] -> [a]
++ [[(Bool, TyCon, [TcType])]] -> [(Bool, TyCon, [TcType])]
forall (t :: * -> *) a. Foldable t => t [a] -> [a]
concat ((ArgFlag -> TcType -> [(Bool, TyCon, [TcType])])
-> [ArgFlag] -> [TcType] -> [[(Bool, TyCon, [TcType])]]
forall a b c. (a -> b -> c) -> [a] -> [b] -> [c]
zipWith (\ArgFlag
flag -> Bool -> TcType -> [(Bool, TyCon, [TcType])]
go (ArgFlag -> Bool
isInvisibleArgFlag ArgFlag
flag))
                            [ArgFlag]
ty_arg_flags [TcType]
ty_args)
    go Bool
is_invis_arg (CastTy TcType
ty KindCoercion
_)      = Bool -> TcType -> [(Bool, TyCon, [TcType])]
go Bool
is_invis_arg TcType
ty
    go Bool
_            (CoercionTy KindCoercion
_)     = [] -- don't count tyfams in coercions,
                                            -- as they never get normalized,
                                            -- anyway

-- | In an application of a 'TyCon' to some arguments, find the outermost
-- occurrences of type family applications within the arguments. This function
-- will not consider the 'TyCon' itself when checking for type family
-- applications.
--
-- See 'tcTyFamInstsAndVis' for more details on how this works (as this
-- function is called inside of 'tcTyFamInstsAndVis').
tcTyConAppTyFamInstsAndVis :: TyCon -> [Type] -> [(Bool, TyCon, [Type])]
tcTyConAppTyFamInstsAndVis :: TyCon -> [TcType] -> [(Bool, TyCon, [TcType])]
tcTyConAppTyFamInstsAndVis = Bool -> TyCon -> [TcType] -> [(Bool, TyCon, [TcType])]
tcTyConAppTyFamInstsAndVisX Bool
False

tcTyConAppTyFamInstsAndVisX
  :: Bool -- ^ Is this an invisible argument to some type application?
  -> TyCon -> [Type] -> [(Bool, TyCon, [Type])]
tcTyConAppTyFamInstsAndVisX :: Bool -> TyCon -> [TcType] -> [(Bool, TyCon, [TcType])]
tcTyConAppTyFamInstsAndVisX Bool
is_invis_arg TyCon
tc [TcType]
tys =
  let ([TcType]
invis_tys, [TcType]
vis_tys) = TyCon -> [TcType] -> ([TcType], [TcType])
partitionInvisibleTypes TyCon
tc [TcType]
tys
  in [[(Bool, TyCon, [TcType])]] -> [(Bool, TyCon, [TcType])]
forall (t :: * -> *) a. Foldable t => t [a] -> [a]
concat ([[(Bool, TyCon, [TcType])]] -> [(Bool, TyCon, [TcType])])
-> [[(Bool, TyCon, [TcType])]] -> [(Bool, TyCon, [TcType])]
forall a b. (a -> b) -> a -> b
$ (TcType -> [(Bool, TyCon, [TcType])])
-> [TcType] -> [[(Bool, TyCon, [TcType])]]
forall a b. (a -> b) -> [a] -> [b]
map (Bool -> TcType -> [(Bool, TyCon, [TcType])]
tcTyFamInstsAndVisX Bool
True)         [TcType]
invis_tys
           [[(Bool, TyCon, [TcType])]]
-> [[(Bool, TyCon, [TcType])]] -> [[(Bool, TyCon, [TcType])]]
forall a. [a] -> [a] -> [a]
++ (TcType -> [(Bool, TyCon, [TcType])])
-> [TcType] -> [[(Bool, TyCon, [TcType])]]
forall a b. (a -> b) -> [a] -> [b]
map (Bool -> TcType -> [(Bool, TyCon, [TcType])]
tcTyFamInstsAndVisX Bool
is_invis_arg) [TcType]
vis_tys

isTyFamFree :: Type -> Bool
-- ^ Check that a type does not contain any type family applications.
isTyFamFree :: TcType -> Bool
isTyFamFree = [(TyCon, [TcType])] -> Bool
forall (t :: * -> *) a. Foldable t => t a -> Bool
null ([(TyCon, [TcType])] -> Bool)
-> (TcType -> [(TyCon, [TcType])]) -> TcType -> Bool
forall b c a. (b -> c) -> (a -> b) -> a -> c
. TcType -> [(TyCon, [TcType])]
tcTyFamInsts

anyRewritableTyVar :: Bool    -- Ignore casts and coercions
                   -> EqRel   -- Ambient role
                   -> (EqRel -> TcTyVar -> Bool)
                   -> TcType -> Bool
-- (anyRewritableTyVar ignore_cos pred ty) returns True
--    if the 'pred' returns True of any free TyVar in 'ty'
-- Do not look inside casts and coercions if 'ignore_cos' is True
-- See Note [anyRewritableTyVar must be role-aware]
anyRewritableTyVar :: Bool -> EqRel -> (EqRel -> TcTyVar -> Bool) -> TcType -> Bool
anyRewritableTyVar Bool
ignore_cos EqRel
role EqRel -> TcTyVar -> Bool
pred TcType
ty
  = EqRel -> VarSet -> TcType -> Bool
go EqRel
role VarSet
emptyVarSet TcType
ty
  where
    go_tv :: EqRel -> VarSet -> TcTyVar -> Bool
go_tv EqRel
rl VarSet
bvs TcTyVar
tv | TcTyVar
tv TcTyVar -> VarSet -> Bool
`elemVarSet` VarSet
bvs = Bool
False
                    | Bool
otherwise           = EqRel -> TcTyVar -> Bool
pred EqRel
rl TcTyVar
tv

    go :: EqRel -> VarSet -> TcType -> Bool
go EqRel
rl VarSet
bvs (TyVarTy TcTyVar
tv)       = EqRel -> VarSet -> TcTyVar -> Bool
go_tv EqRel
rl VarSet
bvs TcTyVar
tv
    go EqRel
_ VarSet
_     (LitTy {})        = Bool
False
    go EqRel
rl VarSet
bvs (TyConApp TyCon
tc [TcType]
tys)  = EqRel -> VarSet -> TyCon -> [TcType] -> Bool
go_tc EqRel
rl VarSet
bvs TyCon
tc [TcType]
tys
    go EqRel
rl VarSet
bvs (AppTy TcType
fun TcType
arg)    = EqRel -> VarSet -> TcType -> Bool
go EqRel
rl VarSet
bvs TcType
fun Bool -> Bool -> Bool
|| EqRel -> VarSet -> TcType -> Bool
go EqRel
NomEq VarSet
bvs TcType
arg
    go EqRel
rl VarSet
bvs (FunTy AnonArgFlag
_ TcType
arg TcType
res)  = EqRel -> VarSet -> TcType -> Bool
go EqRel
rl VarSet
bvs TcType
arg Bool -> Bool -> Bool
|| EqRel -> VarSet -> TcType -> Bool
go EqRel
rl VarSet
bvs TcType
res
    go EqRel
rl VarSet
bvs (ForAllTy TyCoVarBinder
tv TcType
ty)   = EqRel -> VarSet -> TcType -> Bool
go EqRel
rl (VarSet
bvs VarSet -> TcTyVar -> VarSet
`extendVarSet` TyCoVarBinder -> TcTyVar
forall tv argf. VarBndr tv argf -> tv
binderVar TyCoVarBinder
tv) TcType
ty
    go EqRel
rl VarSet
bvs (CastTy TcType
ty KindCoercion
co)     = EqRel -> VarSet -> TcType -> Bool
go EqRel
rl VarSet
bvs TcType
ty Bool -> Bool -> Bool
|| EqRel -> VarSet -> KindCoercion -> Bool
go_co EqRel
rl VarSet
bvs KindCoercion
co
    go EqRel
rl VarSet
bvs (CoercionTy KindCoercion
co)    = EqRel -> VarSet -> KindCoercion -> Bool
go_co EqRel
rl VarSet
bvs KindCoercion
co  -- ToDo: check

    go_tc :: EqRel -> VarSet -> TyCon -> [TcType] -> Bool
go_tc EqRel
NomEq  VarSet
bvs TyCon
_  [TcType]
tys = (TcType -> Bool) -> [TcType] -> Bool
forall (t :: * -> *) a. Foldable t => (a -> Bool) -> t a -> Bool
any (EqRel -> VarSet -> TcType -> Bool
go EqRel
NomEq VarSet
bvs) [TcType]
tys
    go_tc EqRel
ReprEq VarSet
bvs TyCon
tc [TcType]
tys = ((Role, TcType) -> Bool) -> [(Role, TcType)] -> Bool
forall (t :: * -> *) a. Foldable t => (a -> Bool) -> t a -> Bool
any (VarSet -> (Role, TcType) -> Bool
go_arg VarSet
bvs)
                              (TyCon -> [Role]
tyConRolesRepresentational TyCon
tc [Role] -> [TcType] -> [(Role, TcType)]
forall a b. [a] -> [b] -> [(a, b)]
`zip` [TcType]
tys)

    go_arg :: VarSet -> (Role, TcType) -> Bool
go_arg VarSet
bvs (Role
Nominal,          TcType
ty) = EqRel -> VarSet -> TcType -> Bool
go EqRel
NomEq  VarSet
bvs TcType
ty
    go_arg VarSet
bvs (Role
Representational, TcType
ty) = EqRel -> VarSet -> TcType -> Bool
go EqRel
ReprEq VarSet
bvs TcType
ty
    go_arg VarSet
_   (Role
Phantom,          TcType
_)  = Bool
False  -- We never rewrite with phantoms

    go_co :: EqRel -> VarSet -> KindCoercion -> Bool
go_co EqRel
rl VarSet
bvs KindCoercion
co
      | Bool
ignore_cos = Bool
False
      | Bool
otherwise  = (TcTyVar -> Bool) -> VarSet -> Bool
anyVarSet (EqRel -> VarSet -> TcTyVar -> Bool
go_tv EqRel
rl VarSet
bvs) (KindCoercion -> VarSet
tyCoVarsOfCo KindCoercion
co)
      -- We don't have an equivalent of anyRewritableTyVar for coercions
      -- (at least not yet) so take the free vars and test them

{- Note [anyRewritableTyVar must be role-aware]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
anyRewritableTyVar is used during kick-out from the inert set,
to decide if, given a new equality (a ~ ty), we should kick out
a constraint C.  Rather than gather free variables and see if 'a'
is among them, we instead pass in a predicate; this is just efficiency.

Moreover, consider
  work item:   [G] a ~R f b
  inert item:  [G] b ~R f a
We use anyRewritableTyVar to decide whether to kick out the inert item,
on the grounds that the work item might rewrite it. Well, 'a' is certainly
free in [G] b ~R f a.  But because the role of a type variable ('f' in
this case) is nominal, the work item can't actually rewrite the inert item.
Moreover, if we were to kick out the inert item the exact same situation
would re-occur and we end up with an infinite loop in which each kicks
out the other (#14363).
-}

{-
************************************************************************
*                                                                      *
                Predicates
*                                                                      *
************************************************************************
-}

tcIsTcTyVar :: TcTyVar -> Bool
-- See Note [TcTyVars and TyVars in the typechecker]
tcIsTcTyVar :: TcTyVar -> Bool
tcIsTcTyVar TcTyVar
tv = TcTyVar -> Bool
isTyVar TcTyVar
tv

isTouchableMetaTyVar :: TcLevel -> TcTyVar -> Bool
isTouchableMetaTyVar :: TcLevel -> TcTyVar -> Bool
isTouchableMetaTyVar TcLevel
ctxt_tclvl TcTyVar
tv
  | TcTyVar -> Bool
isTyVar TcTyVar
tv -- See Note [Coercion variables in free variable lists]
  , MetaTv { mtv_tclvl :: TcTyVarDetails -> TcLevel
mtv_tclvl = TcLevel
tv_tclvl, mtv_info :: TcTyVarDetails -> MetaInfo
mtv_info = MetaInfo
info } <- TcTyVar -> TcTyVarDetails
tcTyVarDetails TcTyVar
tv
  , Bool -> Bool
not (MetaInfo -> Bool
isFlattenInfo MetaInfo
info)
  = ASSERT2( checkTcLevelInvariant ctxt_tclvl tv_tclvl,
             ppr tv $$ ppr tv_tclvl $$ ppr ctxt_tclvl )
    TcLevel
tv_tclvl TcLevel -> TcLevel -> Bool
`sameDepthAs` TcLevel
ctxt_tclvl

  | Bool
otherwise = Bool
False

isFloatedTouchableMetaTyVar :: TcLevel -> TcTyVar -> Bool
isFloatedTouchableMetaTyVar :: TcLevel -> TcTyVar -> Bool
isFloatedTouchableMetaTyVar TcLevel
ctxt_tclvl TcTyVar
tv
  | TcTyVar -> Bool
isTyVar TcTyVar
tv -- See Note [Coercion variables in free variable lists]
  , MetaTv { mtv_tclvl :: TcTyVarDetails -> TcLevel
mtv_tclvl = TcLevel
tv_tclvl, mtv_info :: TcTyVarDetails -> MetaInfo
mtv_info = MetaInfo
info } <- TcTyVar -> TcTyVarDetails
tcTyVarDetails TcTyVar
tv
  , Bool -> Bool
not (MetaInfo -> Bool
isFlattenInfo MetaInfo
info)
  = TcLevel
tv_tclvl TcLevel -> TcLevel -> Bool
`strictlyDeeperThan` TcLevel
ctxt_tclvl

  | Bool
otherwise = Bool
False

isImmutableTyVar :: TyVar -> Bool
isImmutableTyVar :: TcTyVar -> Bool
isImmutableTyVar TcTyVar
tv = TcTyVar -> Bool
isSkolemTyVar TcTyVar
tv

isTyConableTyVar, isSkolemTyVar, isOverlappableTyVar,
  isMetaTyVar, isAmbiguousTyVar,
  isFmvTyVar, isFskTyVar, isFlattenTyVar :: TcTyVar -> Bool

isTyConableTyVar :: TcTyVar -> Bool
isTyConableTyVar TcTyVar
tv
        -- True of a meta-type variable that can be filled in
        -- with a type constructor application; in particular,
        -- not a TyVarTv
  | TcTyVar -> Bool
isTyVar TcTyVar
tv -- See Note [Coercion variables in free variable lists]
  = case TcTyVar -> TcTyVarDetails
tcTyVarDetails TcTyVar
tv of
        MetaTv { mtv_info :: TcTyVarDetails -> MetaInfo
mtv_info = MetaInfo
TyVarTv } -> Bool
False
        TcTyVarDetails
_                             -> Bool
True
  | Bool
otherwise = Bool
True

isFmvTyVar :: TcTyVar -> Bool
isFmvTyVar TcTyVar
tv
  = ASSERT2( tcIsTcTyVar tv, ppr tv )
    case TcTyVar -> TcTyVarDetails
tcTyVarDetails TcTyVar
tv of
        MetaTv { mtv_info :: TcTyVarDetails -> MetaInfo
mtv_info = MetaInfo
FlatMetaTv } -> Bool
True
        TcTyVarDetails
_                                -> Bool
False

isFskTyVar :: TcTyVar -> Bool
isFskTyVar TcTyVar
tv
  = ASSERT2( tcIsTcTyVar tv, ppr tv )
    case TcTyVar -> TcTyVarDetails
tcTyVarDetails TcTyVar
tv of
        MetaTv { mtv_info :: TcTyVarDetails -> MetaInfo
mtv_info = MetaInfo
FlatSkolTv } -> Bool
True
        TcTyVarDetails
_                                -> Bool
False

-- | True of both given and wanted flatten-skolems (fmv and fsk)
isFlattenTyVar :: TcTyVar -> Bool
isFlattenTyVar TcTyVar
tv
  = ASSERT2( tcIsTcTyVar tv, ppr tv )
    case TcTyVar -> TcTyVarDetails
tcTyVarDetails TcTyVar
tv of
        MetaTv { mtv_info :: TcTyVarDetails -> MetaInfo
mtv_info = MetaInfo
info } -> MetaInfo -> Bool
isFlattenInfo MetaInfo
info
        TcTyVarDetails
_                          -> Bool
False

isSkolemTyVar :: TcTyVar -> Bool
isSkolemTyVar TcTyVar
tv
  = ASSERT2( tcIsTcTyVar tv, ppr tv )
    case TcTyVar -> TcTyVarDetails
tcTyVarDetails TcTyVar
tv of
        MetaTv {} -> Bool
False
        TcTyVarDetails
_other    -> Bool
True

isOverlappableTyVar :: TcTyVar -> Bool
isOverlappableTyVar TcTyVar
tv
  | TcTyVar -> Bool
isTyVar TcTyVar
tv -- See Note [Coercion variables in free variable lists]
  = case TcTyVar -> TcTyVarDetails
tcTyVarDetails TcTyVar
tv of
        SkolemTv TcLevel
_ Bool
overlappable -> Bool
overlappable
        TcTyVarDetails
_                       -> Bool
False
  | Bool
otherwise = Bool
False

isMetaTyVar :: TcTyVar -> Bool
isMetaTyVar TcTyVar
tv
  | TcTyVar -> Bool
isTyVar TcTyVar
tv -- See Note [Coercion variables in free variable lists]
  = case TcTyVar -> TcTyVarDetails
tcTyVarDetails TcTyVar
tv of
        MetaTv {} -> Bool
True
        TcTyVarDetails
_         -> Bool
False
  | Bool
otherwise = Bool
False

-- isAmbiguousTyVar is used only when reporting type errors
-- It picks out variables that are unbound, namely meta
-- type variables and the RuntimUnk variables created by
-- RtClosureInspect.zonkRTTIType.  These are "ambiguous" in
-- the sense that they stand for an as-yet-unknown type
isAmbiguousTyVar :: TcTyVar -> Bool
isAmbiguousTyVar TcTyVar
tv
  | TcTyVar -> Bool
isTyVar TcTyVar
tv -- See Note [Coercion variables in free variable lists]
  = case TcTyVar -> TcTyVarDetails
tcTyVarDetails TcTyVar
tv of
        MetaTv {}     -> Bool
True
        RuntimeUnk {} -> Bool
True
        TcTyVarDetails
_             -> Bool
False
  | Bool
otherwise = Bool
False

isMetaTyVarTy :: TcType -> Bool
isMetaTyVarTy :: TcType -> Bool
isMetaTyVarTy (TyVarTy TcTyVar
tv) = TcTyVar -> Bool
isMetaTyVar TcTyVar
tv
isMetaTyVarTy TcType
_            = Bool
False

metaTyVarInfo :: TcTyVar -> MetaInfo
metaTyVarInfo :: TcTyVar -> MetaInfo
metaTyVarInfo TcTyVar
tv
  = case TcTyVar -> TcTyVarDetails
tcTyVarDetails TcTyVar
tv of
      MetaTv { mtv_info :: TcTyVarDetails -> MetaInfo
mtv_info = MetaInfo
info } -> MetaInfo
info
      TcTyVarDetails
_ -> String -> SDoc -> MetaInfo
forall a. HasCallStack => String -> SDoc -> a
pprPanic String
"metaTyVarInfo" (TcTyVar -> SDoc
forall a. Outputable a => a -> SDoc
ppr TcTyVar
tv)

isFlattenInfo :: MetaInfo -> Bool
isFlattenInfo :: MetaInfo -> Bool
isFlattenInfo MetaInfo
FlatMetaTv = Bool
True
isFlattenInfo MetaInfo
FlatSkolTv = Bool
True
isFlattenInfo MetaInfo
_          = Bool
False

metaTyVarTcLevel :: TcTyVar -> TcLevel
metaTyVarTcLevel :: TcTyVar -> TcLevel
metaTyVarTcLevel TcTyVar
tv
  = case TcTyVar -> TcTyVarDetails
tcTyVarDetails TcTyVar
tv of
      MetaTv { mtv_tclvl :: TcTyVarDetails -> TcLevel
mtv_tclvl = TcLevel
tclvl } -> TcLevel
tclvl
      TcTyVarDetails
_ -> String -> SDoc -> TcLevel
forall a. HasCallStack => String -> SDoc -> a
pprPanic String
"metaTyVarTcLevel" (TcTyVar -> SDoc
forall a. Outputable a => a -> SDoc
ppr TcTyVar
tv)

metaTyVarTcLevel_maybe :: TcTyVar -> Maybe TcLevel
metaTyVarTcLevel_maybe :: TcTyVar -> Maybe TcLevel
metaTyVarTcLevel_maybe TcTyVar
tv
  = case TcTyVar -> TcTyVarDetails
tcTyVarDetails TcTyVar
tv of
      MetaTv { mtv_tclvl :: TcTyVarDetails -> TcLevel
mtv_tclvl = TcLevel
tclvl } -> TcLevel -> Maybe TcLevel
forall a. a -> Maybe a
Just TcLevel
tclvl
      TcTyVarDetails
_                            -> Maybe TcLevel
forall a. Maybe a
Nothing

metaTyVarRef :: TyVar -> IORef MetaDetails
metaTyVarRef :: TcTyVar -> IORef MetaDetails
metaTyVarRef TcTyVar
tv
  = case TcTyVar -> TcTyVarDetails
tcTyVarDetails TcTyVar
tv of
        MetaTv { mtv_ref :: TcTyVarDetails -> IORef MetaDetails
mtv_ref = IORef MetaDetails
ref } -> IORef MetaDetails
ref
        TcTyVarDetails
_ -> String -> SDoc -> IORef MetaDetails
forall a. HasCallStack => String -> SDoc -> a
pprPanic String
"metaTyVarRef" (TcTyVar -> SDoc
forall a. Outputable a => a -> SDoc
ppr TcTyVar
tv)

setMetaTyVarTcLevel :: TcTyVar -> TcLevel -> TcTyVar
setMetaTyVarTcLevel :: TcTyVar -> TcLevel -> TcTyVar
setMetaTyVarTcLevel TcTyVar
tv TcLevel
tclvl
  = case TcTyVar -> TcTyVarDetails
tcTyVarDetails TcTyVar
tv of
      details :: TcTyVarDetails
details@(MetaTv {}) -> TcTyVar -> TcTyVarDetails -> TcTyVar
setTcTyVarDetails TcTyVar
tv (TcTyVarDetails
details { mtv_tclvl :: TcLevel
mtv_tclvl = TcLevel
tclvl })
      TcTyVarDetails
_ -> String -> SDoc -> TcTyVar
forall a. HasCallStack => String -> SDoc -> a
pprPanic String
"metaTyVarTcLevel" (TcTyVar -> SDoc
forall a. Outputable a => a -> SDoc
ppr TcTyVar
tv)

isTyVarTyVar :: Var -> Bool
isTyVarTyVar :: TcTyVar -> Bool
isTyVarTyVar TcTyVar
tv
  = case TcTyVar -> TcTyVarDetails
tcTyVarDetails TcTyVar
tv of
        MetaTv { mtv_info :: TcTyVarDetails -> MetaInfo
mtv_info = MetaInfo
TyVarTv } -> Bool
True
        TcTyVarDetails
_                             -> Bool
False

isFlexi, isIndirect :: MetaDetails -> Bool
isFlexi :: MetaDetails -> Bool
isFlexi MetaDetails
Flexi = Bool
True
isFlexi MetaDetails
_     = Bool
False

isIndirect :: MetaDetails -> Bool
isIndirect (Indirect TcType
_) = Bool
True
isIndirect MetaDetails
_            = Bool
False

isRuntimeUnkSkol :: TyVar -> Bool
-- Called only in TcErrors; see Note [Runtime skolems] there
isRuntimeUnkSkol :: TcTyVar -> Bool
isRuntimeUnkSkol TcTyVar
x
  | TcTyVarDetails
RuntimeUnk <- TcTyVar -> TcTyVarDetails
tcTyVarDetails TcTyVar
x = Bool
True
  | Bool
otherwise                      = Bool
False

mkTyVarNamePairs :: [TyVar] -> [(Name,TyVar)]
-- Just pair each TyVar with its own name
mkTyVarNamePairs :: [TcTyVar] -> [(Name, TcTyVar)]
mkTyVarNamePairs [TcTyVar]
tvs = [(TcTyVar -> Name
tyVarName TcTyVar
tv, TcTyVar
tv) | TcTyVar
tv <- [TcTyVar]
tvs]

findDupTyVarTvs :: [(Name,TcTyVar)] -> [(Name,Name)]
-- If we have [...(x1,tv)...(x2,tv)...]
-- return (x1,x2) in the result list
findDupTyVarTvs :: [(Name, TcTyVar)] -> [(Name, Name)]
findDupTyVarTvs [(Name, TcTyVar)]
prs
  = (NonEmpty (Name, TcTyVar) -> [(Name, Name)])
-> [NonEmpty (Name, TcTyVar)] -> [(Name, Name)]
forall (t :: * -> *) a b. Foldable t => (a -> [b]) -> t a -> [b]
concatMap NonEmpty (Name, TcTyVar) -> [(Name, Name)]
forall b b. NonEmpty (b, b) -> [(b, b)]
mk_result_prs ([NonEmpty (Name, TcTyVar)] -> [(Name, Name)])
-> [NonEmpty (Name, TcTyVar)] -> [(Name, Name)]
forall a b. (a -> b) -> a -> b
$
    ((Name, TcTyVar) -> (Name, TcTyVar) -> Bool)
-> [(Name, TcTyVar)] -> [NonEmpty (Name, TcTyVar)]
forall a. (a -> a -> Bool) -> [a] -> [NonEmpty a]
findDupsEq (Name, TcTyVar) -> (Name, TcTyVar) -> Bool
forall a a a. Eq a => (a, a) -> (a, a) -> Bool
eq_snd [(Name, TcTyVar)]
prs
  where
    eq_snd :: (a, a) -> (a, a) -> Bool
eq_snd (a
_,a
tv1) (a
_,a
tv2) = a
tv1 a -> a -> Bool
forall a. Eq a => a -> a -> Bool
== a
tv2
    mk_result_prs :: NonEmpty (b, b) -> [(b, b)]
mk_result_prs ((b
n1,b
_) :| [(b, b)]
xs) = ((b, b) -> (b, b)) -> [(b, b)] -> [(b, b)]
forall a b. (a -> b) -> [a] -> [b]
map (\(b
n2,b
_) -> (b
n1,b
n2)) [(b, b)]
xs

{-
************************************************************************
*                                                                      *
\subsection{Tau, sigma and rho}
*                                                                      *
************************************************************************
-}

mkSigmaTy :: [TyCoVarBinder] -> [PredType] -> Type -> Type
mkSigmaTy :: [TyCoVarBinder] -> [TcType] -> TcType -> TcType
mkSigmaTy [TyCoVarBinder]
bndrs [TcType]
theta TcType
tau = [TyCoVarBinder] -> TcType -> TcType
mkForAllTys [TyCoVarBinder]
bndrs ([TcType] -> TcType -> TcType
mkPhiTy [TcType]
theta TcType
tau)

-- | Make a sigma ty where all type variables are 'Inferred'. That is,
-- they cannot be used with visible type application.
mkInfSigmaTy :: [TyCoVar] -> [PredType] -> Type -> Type
mkInfSigmaTy :: [TcTyVar] -> [TcType] -> TcType -> TcType
mkInfSigmaTy [TcTyVar]
tyvars [TcType]
theta TcType
ty = [TyCoVarBinder] -> [TcType] -> TcType -> TcType
mkSigmaTy (ArgFlag -> [TcTyVar] -> [TyCoVarBinder]
mkTyCoVarBinders ArgFlag
Inferred [TcTyVar]
tyvars) [TcType]
theta TcType
ty

-- | Make a sigma ty where all type variables are "specified". That is,
-- they can be used with visible type application
mkSpecSigmaTy :: [TyVar] -> [PredType] -> Type -> Type
mkSpecSigmaTy :: [TcTyVar] -> [TcType] -> TcType -> TcType
mkSpecSigmaTy [TcTyVar]
tyvars [TcType]
preds TcType
ty = [TyCoVarBinder] -> [TcType] -> TcType -> TcType
mkSigmaTy (ArgFlag -> [TcTyVar] -> [TyCoVarBinder]
mkTyCoVarBinders ArgFlag
Specified [TcTyVar]
tyvars) [TcType]
preds TcType
ty

mkPhiTy :: [PredType] -> Type -> Type
mkPhiTy :: [TcType] -> TcType -> TcType
mkPhiTy = [TcType] -> TcType -> TcType
mkInvisFunTys

---------------
getDFunTyKey :: Type -> OccName -- Get some string from a type, to be used to
                                -- construct a dictionary function name
getDFunTyKey :: TcType -> OccName
getDFunTyKey TcType
ty | Just TcType
ty' <- TcType -> Maybe TcType
coreView TcType
ty = TcType -> OccName
getDFunTyKey TcType
ty'
getDFunTyKey (TyVarTy TcTyVar
tv)            = TcTyVar -> OccName
forall a. NamedThing a => a -> OccName
getOccName TcTyVar
tv
getDFunTyKey (TyConApp TyCon
tc [TcType]
_)         = TyCon -> OccName
forall a. NamedThing a => a -> OccName
getOccName TyCon
tc
getDFunTyKey (LitTy TyLit
x)               = TyLit -> OccName
getDFunTyLitKey TyLit
x
getDFunTyKey (AppTy TcType
fun TcType
_)           = TcType -> OccName
getDFunTyKey TcType
fun
getDFunTyKey (FunTy {})              = TyCon -> OccName
forall a. NamedThing a => a -> OccName
getOccName TyCon
funTyCon
getDFunTyKey (ForAllTy TyCoVarBinder
_ TcType
t)          = TcType -> OccName
getDFunTyKey TcType
t
getDFunTyKey (CastTy TcType
ty KindCoercion
_)           = TcType -> OccName
getDFunTyKey TcType
ty
getDFunTyKey t :: TcType
t@(CoercionTy KindCoercion
_)        = String -> SDoc -> OccName
forall a. HasCallStack => String -> SDoc -> a
pprPanic String
"getDFunTyKey" (TcType -> SDoc
forall a. Outputable a => a -> SDoc
ppr TcType
t)

getDFunTyLitKey :: TyLit -> OccName
getDFunTyLitKey :: TyLit -> OccName
getDFunTyLitKey (NumTyLit Integer
n) = NameSpace -> String -> OccName
mkOccName NameSpace
Name.varName (Integer -> String
forall a. Show a => a -> String
show Integer
n)
getDFunTyLitKey (StrTyLit FastString
n) = NameSpace -> String -> OccName
mkOccName NameSpace
Name.varName (FastString -> String
forall a. Show a => a -> String
show FastString
n)  -- hm

{- *********************************************************************
*                                                                      *
           Building types
*                                                                      *
********************************************************************* -}

-- ToDo: I think we need Tc versions of these
-- Reason: mkCastTy checks isReflexiveCastTy, which checks
--         for equality; and that has a different answer
--         depending on whether or not Type = Constraint

mkTcAppTys :: Type -> [Type] -> Type
mkTcAppTys :: TcType -> [TcType] -> TcType
mkTcAppTys = TcType -> [TcType] -> TcType
mkAppTys

mkTcAppTy :: Type -> Type -> Type
mkTcAppTy :: TcType -> TcType -> TcType
mkTcAppTy = TcType -> TcType -> TcType
mkAppTy

mkTcCastTy :: Type -> Coercion -> Type
mkTcCastTy :: TcType -> KindCoercion -> TcType
mkTcCastTy = TcType -> KindCoercion -> TcType
mkCastTy   -- Do we need a tc version of mkCastTy?

{-
************************************************************************
*                                                                      *
\subsection{Expanding and splitting}
*                                                                      *
************************************************************************

These tcSplit functions are like their non-Tc analogues, but
        *) they do not look through newtypes

However, they are non-monadic and do not follow through mutable type
variables.  It's up to you to make sure this doesn't matter.
-}

-- | Splits a forall type into a list of 'TyBinder's and the inner type.
-- Always succeeds, even if it returns an empty list.
tcSplitPiTys :: Type -> ([TyBinder], Type)
tcSplitPiTys :: TcType -> ([TyBinder], TcType)
tcSplitPiTys TcType
ty
  = ASSERT( all isTyBinder (fst sty) ) sty
  where sty :: ([TyBinder], TcType)
sty = TcType -> ([TyBinder], TcType)
splitPiTys TcType
ty

-- | Splits a type into a TyBinder and a body, if possible. Panics otherwise
tcSplitPiTy_maybe :: Type -> Maybe (TyBinder, Type)
tcSplitPiTy_maybe :: TcType -> Maybe (TyBinder, TcType)
tcSplitPiTy_maybe TcType
ty
  = ASSERT( isMaybeTyBinder sty ) sty
  where
    sty :: Maybe (TyBinder, TcType)
sty = TcType -> Maybe (TyBinder, TcType)
splitPiTy_maybe TcType
ty
    isMaybeTyBinder :: Maybe (TyBinder, b) -> Bool
isMaybeTyBinder (Just (TyBinder
t,b
_)) = TyBinder -> Bool
isTyBinder TyBinder
t
    isMaybeTyBinder Maybe (TyBinder, b)
_            = Bool
True

tcSplitForAllTy_maybe :: Type -> Maybe (TyVarBinder, Type)
tcSplitForAllTy_maybe :: TcType -> Maybe (TyCoVarBinder, TcType)
tcSplitForAllTy_maybe TcType
ty | Just TcType
ty' <- TcType -> Maybe TcType
tcView TcType
ty = TcType -> Maybe (TyCoVarBinder, TcType)
tcSplitForAllTy_maybe TcType
ty'
tcSplitForAllTy_maybe (ForAllTy TyCoVarBinder
tv TcType
ty) = ASSERT( isTyVarBinder tv ) Just (tv, ty)
tcSplitForAllTy_maybe TcType
_                = Maybe (TyCoVarBinder, TcType)
forall a. Maybe a
Nothing

-- | Like 'tcSplitPiTys', but splits off only named binders,
-- returning just the tycovars.
tcSplitForAllTys :: Type -> ([TyVar], Type)
tcSplitForAllTys :: TcType -> ([TcTyVar], TcType)
tcSplitForAllTys TcType
ty
  = ASSERT( all isTyVar (fst sty) ) sty
  where sty :: ([TcTyVar], TcType)
sty = TcType -> ([TcTyVar], TcType)
splitForAllTys TcType
ty

-- | Like 'tcSplitForAllTys', but only splits a 'ForAllTy' if
-- @'sameVis' argf supplied_argf@ is 'True', where @argf@ is the visibility
-- of the @ForAllTy@'s binder and @supplied_argf@ is the visibility provided
-- as an argument to this function.
tcSplitForAllTysSameVis :: ArgFlag -> Type -> ([TyVar], Type)
tcSplitForAllTysSameVis :: ArgFlag -> TcType -> ([TcTyVar], TcType)
tcSplitForAllTysSameVis ArgFlag
supplied_argf TcType
ty = ASSERT( all isTyVar (fst sty) ) sty
  where sty :: ([TcTyVar], TcType)
sty = ArgFlag -> TcType -> ([TcTyVar], TcType)
splitForAllTysSameVis ArgFlag
supplied_argf TcType
ty

-- | Like 'tcSplitForAllTys', but splits off only named binders.
tcSplitForAllVarBndrs :: Type -> ([TyVarBinder], Type)
tcSplitForAllVarBndrs :: TcType -> ([TyCoVarBinder], TcType)
tcSplitForAllVarBndrs TcType
ty = ASSERT( all isTyVarBinder (fst sty)) sty
  where sty :: ([TyCoVarBinder], TcType)
sty = TcType -> ([TyCoVarBinder], TcType)
splitForAllVarBndrs TcType
ty

-- | Is this a ForAllTy with a named binder?
tcIsForAllTy :: Type -> Bool
tcIsForAllTy :: TcType -> Bool
tcIsForAllTy TcType
ty | Just TcType
ty' <- TcType -> Maybe TcType
tcView TcType
ty = TcType -> Bool
tcIsForAllTy TcType
ty'
tcIsForAllTy (ForAllTy {}) = Bool
True
tcIsForAllTy TcType
_             = Bool
False

tcSplitPredFunTy_maybe :: Type -> Maybe (PredType, Type)
-- Split off the first predicate argument from a type
tcSplitPredFunTy_maybe :: TcType -> Maybe (TcType, TcType)
tcSplitPredFunTy_maybe TcType
ty
  | Just TcType
ty' <- TcType -> Maybe TcType
tcView TcType
ty = TcType -> Maybe (TcType, TcType)
tcSplitPredFunTy_maybe TcType
ty'
tcSplitPredFunTy_maybe (FunTy { ft_af :: TcType -> AnonArgFlag
ft_af = AnonArgFlag
InvisArg
                              , ft_arg :: TcType -> TcType
ft_arg = TcType
arg, ft_res :: TcType -> TcType
ft_res = TcType
res })
  = (TcType, TcType) -> Maybe (TcType, TcType)
forall a. a -> Maybe a
Just (TcType
arg, TcType
res)
tcSplitPredFunTy_maybe TcType
_
  = Maybe (TcType, TcType)
forall a. Maybe a
Nothing

tcSplitPhiTy :: Type -> (ThetaType, Type)
tcSplitPhiTy :: TcType -> ([TcType], TcType)
tcSplitPhiTy TcType
ty
  = TcType -> [TcType] -> ([TcType], TcType)
split TcType
ty []
  where
    split :: TcType -> [TcType] -> ([TcType], TcType)
split TcType
ty [TcType]
ts
      = case TcType -> Maybe (TcType, TcType)
tcSplitPredFunTy_maybe TcType
ty of
          Just (TcType
pred, TcType
ty) -> TcType -> [TcType] -> ([TcType], TcType)
split TcType
ty (TcType
predTcType -> [TcType] -> [TcType]
forall a. a -> [a] -> [a]
:[TcType]
ts)
          Maybe (TcType, TcType)
Nothing         -> ([TcType] -> [TcType]
forall a. [a] -> [a]
reverse [TcType]
ts, TcType
ty)

-- | Split a sigma type into its parts.
tcSplitSigmaTy :: Type -> ([TyVar], ThetaType, Type)
tcSplitSigmaTy :: TcType -> ([TcTyVar], [TcType], TcType)
tcSplitSigmaTy TcType
ty = case TcType -> ([TcTyVar], TcType)
tcSplitForAllTys TcType
ty of
                        ([TcTyVar]
tvs, TcType
rho) -> case TcType -> ([TcType], TcType)
tcSplitPhiTy TcType
rho of
                                        ([TcType]
theta, TcType
tau) -> ([TcTyVar]
tvs, [TcType]
theta, TcType
tau)

-- | Split a sigma type into its parts, going underneath as many @ForAllTy@s
-- as possible. For example, given this type synonym:
--
-- @
-- type Traversal s t a b = forall f. Applicative f => (a -> f b) -> s -> f t
-- @
--
-- if you called @tcSplitSigmaTy@ on this type:
--
-- @
-- forall s t a b. Each s t a b => Traversal s t a b
-- @
--
-- then it would return @([s,t,a,b], [Each s t a b], Traversal s t a b)@. But
-- if you instead called @tcSplitNestedSigmaTys@ on the type, it would return
-- @([s,t,a,b,f], [Each s t a b, Applicative f], (a -> f b) -> s -> f t)@.
tcSplitNestedSigmaTys :: Type -> ([TyVar], ThetaType, Type)
-- NB: This is basically a pure version of deeplyInstantiate (from Inst) that
-- doesn't compute an HsWrapper.
tcSplitNestedSigmaTys :: TcType -> ([TcTyVar], [TcType], TcType)
tcSplitNestedSigmaTys TcType
ty
    -- If there's a forall, split it apart and try splitting the rho type
    -- underneath it.
  | Just ([TcType]
arg_tys, [TcTyVar]
tvs1, [TcType]
theta1, TcType
rho1) <- TcType -> Maybe ([TcType], [TcTyVar], [TcType], TcType)
tcDeepSplitSigmaTy_maybe TcType
ty
  = let ([TcTyVar]
tvs2, [TcType]
theta2, TcType
rho2) = TcType -> ([TcTyVar], [TcType], TcType)
tcSplitNestedSigmaTys TcType
rho1
    in ([TcTyVar]
tvs1 [TcTyVar] -> [TcTyVar] -> [TcTyVar]
forall a. [a] -> [a] -> [a]
++ [TcTyVar]
tvs2, [TcType]
theta1 [TcType] -> [TcType] -> [TcType]
forall a. [a] -> [a] -> [a]
++ [TcType]
theta2, [TcType] -> TcType -> TcType
mkVisFunTys [TcType]
arg_tys TcType
rho2)
    -- If there's no forall, we're done.
  | Bool
otherwise = ([], [], TcType
ty)

-----------------------
tcDeepSplitSigmaTy_maybe
  :: TcSigmaType -> Maybe ([TcType], [TyVar], ThetaType, TcSigmaType)
-- Looks for a *non-trivial* quantified type, under zero or more function arrows
-- By "non-trivial" we mean either tyvars or constraints are non-empty

tcDeepSplitSigmaTy_maybe :: TcType -> Maybe ([TcType], [TcTyVar], [TcType], TcType)
tcDeepSplitSigmaTy_maybe TcType
ty
  | Just (TcType
arg_ty, TcType
res_ty)           <- TcType -> Maybe (TcType, TcType)
tcSplitFunTy_maybe TcType
ty
  , Just ([TcType]
arg_tys, [TcTyVar]
tvs, [TcType]
theta, TcType
rho) <- TcType -> Maybe ([TcType], [TcTyVar], [TcType], TcType)
tcDeepSplitSigmaTy_maybe TcType
res_ty
  = ([TcType], [TcTyVar], [TcType], TcType)
-> Maybe ([TcType], [TcTyVar], [TcType], TcType)
forall a. a -> Maybe a
Just (TcType
arg_tyTcType -> [TcType] -> [TcType]
forall a. a -> [a] -> [a]
:[TcType]
arg_tys, [TcTyVar]
tvs, [TcType]
theta, TcType
rho)

  | ([TcTyVar]
tvs, [TcType]
theta, TcType
rho) <- TcType -> ([TcTyVar], [TcType], TcType)
tcSplitSigmaTy TcType
ty
  , Bool -> Bool
not ([TcTyVar] -> Bool
forall (t :: * -> *) a. Foldable t => t a -> Bool
null [TcTyVar]
tvs Bool -> Bool -> Bool
&& [TcType] -> Bool
forall (t :: * -> *) a. Foldable t => t a -> Bool
null [TcType]
theta)
  = ([TcType], [TcTyVar], [TcType], TcType)
-> Maybe ([TcType], [TcTyVar], [TcType], TcType)
forall a. a -> Maybe a
Just ([], [TcTyVar]
tvs, [TcType]
theta, TcType
rho)

  | Bool
otherwise = Maybe ([TcType], [TcTyVar], [TcType], TcType)
forall a. Maybe a
Nothing

-----------------------
tcTyConAppTyCon :: Type -> TyCon
tcTyConAppTyCon :: TcType -> TyCon
tcTyConAppTyCon TcType
ty
  = case TcType -> Maybe TyCon
tcTyConAppTyCon_maybe TcType
ty of
      Just TyCon
tc -> TyCon
tc
      Maybe TyCon
Nothing -> String -> SDoc -> TyCon
forall a. HasCallStack => String -> SDoc -> a
pprPanic String
"tcTyConAppTyCon" (TcType -> SDoc
pprType TcType
ty)

-- | Like 'tcRepSplitTyConApp_maybe', but only returns the 'TyCon'.
tcTyConAppTyCon_maybe :: Type -> Maybe TyCon
tcTyConAppTyCon_maybe :: TcType -> Maybe TyCon
tcTyConAppTyCon_maybe TcType
ty
  | Just TcType
ty' <- TcType -> Maybe TcType
tcView TcType
ty = TcType -> Maybe TyCon
tcTyConAppTyCon_maybe TcType
ty'
tcTyConAppTyCon_maybe (TyConApp TyCon
tc [TcType]
_)
  = TyCon -> Maybe TyCon
forall a. a -> Maybe a
Just TyCon
tc
tcTyConAppTyCon_maybe (FunTy { ft_af :: TcType -> AnonArgFlag
ft_af = AnonArgFlag
VisArg })
  = TyCon -> Maybe TyCon
forall a. a -> Maybe a
Just TyCon
funTyCon  -- (=>) is /not/ a TyCon in its own right
                   -- C.f. tcRepSplitAppTy_maybe
tcTyConAppTyCon_maybe TcType
_
  = Maybe TyCon
forall a. Maybe a
Nothing

tcTyConAppArgs :: Type -> [Type]
tcTyConAppArgs :: TcType -> [TcType]
tcTyConAppArgs TcType
ty = case HasCallStack => TcType -> Maybe (TyCon, [TcType])
TcType -> Maybe (TyCon, [TcType])
tcSplitTyConApp_maybe TcType
ty of
                        Just (TyCon
_, [TcType]
args) -> [TcType]
args
                        Maybe (TyCon, [TcType])
Nothing        -> String -> SDoc -> [TcType]
forall a. HasCallStack => String -> SDoc -> a
pprPanic String
"tcTyConAppArgs" (TcType -> SDoc
pprType TcType
ty)

tcSplitTyConApp :: Type -> (TyCon, [Type])
tcSplitTyConApp :: TcType -> (TyCon, [TcType])
tcSplitTyConApp TcType
ty = case HasCallStack => TcType -> Maybe (TyCon, [TcType])
TcType -> Maybe (TyCon, [TcType])
tcSplitTyConApp_maybe TcType
ty of
                        Just (TyCon, [TcType])
stuff -> (TyCon, [TcType])
stuff
                        Maybe (TyCon, [TcType])
Nothing    -> String -> SDoc -> (TyCon, [TcType])
forall a. HasCallStack => String -> SDoc -> a
pprPanic String
"tcSplitTyConApp" (TcType -> SDoc
pprType TcType
ty)

-----------------------
tcSplitFunTys :: Type -> ([Type], Type)
tcSplitFunTys :: TcType -> ([TcType], TcType)
tcSplitFunTys TcType
ty = case TcType -> Maybe (TcType, TcType)
tcSplitFunTy_maybe TcType
ty of
                        Maybe (TcType, TcType)
Nothing        -> ([], TcType
ty)
                        Just (TcType
arg,TcType
res) -> (TcType
argTcType -> [TcType] -> [TcType]
forall a. a -> [a] -> [a]
:[TcType]
args, TcType
res')
                                       where
                                          ([TcType]
args,TcType
res') = TcType -> ([TcType], TcType)
tcSplitFunTys TcType
res

tcSplitFunTy_maybe :: Type -> Maybe (Type, Type)
tcSplitFunTy_maybe :: TcType -> Maybe (TcType, TcType)
tcSplitFunTy_maybe TcType
ty
  | Just TcType
ty' <- TcType -> Maybe TcType
tcView TcType
ty = TcType -> Maybe (TcType, TcType)
tcSplitFunTy_maybe TcType
ty'
tcSplitFunTy_maybe (FunTy { ft_af :: TcType -> AnonArgFlag
ft_af = AnonArgFlag
af, ft_arg :: TcType -> TcType
ft_arg = TcType
arg, ft_res :: TcType -> TcType
ft_res = TcType
res })
  | AnonArgFlag
VisArg <- AnonArgFlag
af = (TcType, TcType) -> Maybe (TcType, TcType)
forall a. a -> Maybe a
Just (TcType
arg, TcType
res)
tcSplitFunTy_maybe TcType
_ = Maybe (TcType, TcType)
forall a. Maybe a
Nothing
        -- Note the VisArg guard
        -- Consider     (?x::Int) => Bool
        -- We don't want to treat this as a function type!
        -- A concrete example is test tc230:
        --      f :: () -> (?p :: ()) => () -> ()
        --
        --      g = f () ()

tcSplitFunTysN :: Arity                      -- n: Number of desired args
               -> TcRhoType
               -> Either Arity               -- Number of missing arrows
                        ([TcSigmaType],      -- Arg types (always N types)
                         TcSigmaType)        -- The rest of the type
-- ^ Split off exactly the specified number argument types
-- Returns
--  (Left m) if there are 'm' missing arrows in the type
--  (Right (tys,res)) if the type looks like t1 -> ... -> tn -> res
tcSplitFunTysN :: Int -> TcType -> Either Int ([TcType], TcType)
tcSplitFunTysN Int
n TcType
ty
 | Int
n Int -> Int -> Bool
forall a. Eq a => a -> a -> Bool
== Int
0
 = ([TcType], TcType) -> Either Int ([TcType], TcType)
forall a b. b -> Either a b
Right ([], TcType
ty)
 | Just (TcType
arg,TcType
res) <- TcType -> Maybe (TcType, TcType)
tcSplitFunTy_maybe TcType
ty
 = case Int -> TcType -> Either Int ([TcType], TcType)
tcSplitFunTysN (Int
nInt -> Int -> Int
forall a. Num a => a -> a -> a
-Int
1) TcType
res of
     Left Int
m            -> Int -> Either Int ([TcType], TcType)
forall a b. a -> Either a b
Left Int
m
     Right ([TcType]
args,TcType
body) -> ([TcType], TcType) -> Either Int ([TcType], TcType)
forall a b. b -> Either a b
Right (TcType
argTcType -> [TcType] -> [TcType]
forall a. a -> [a] -> [a]
:[TcType]
args, TcType
body)
 | Bool
otherwise
 = Int -> Either Int ([TcType], TcType)
forall a b. a -> Either a b
Left Int
n

tcSplitFunTy :: Type -> (Type, Type)
tcSplitFunTy :: TcType -> (TcType, TcType)
tcSplitFunTy  TcType
ty = String -> Maybe (TcType, TcType) -> (TcType, TcType)
forall a. HasCallStack => String -> Maybe a -> a
expectJust String
"tcSplitFunTy" (TcType -> Maybe (TcType, TcType)
tcSplitFunTy_maybe TcType
ty)

tcFunArgTy :: Type -> Type
tcFunArgTy :: TcType -> TcType
tcFunArgTy    TcType
ty = (TcType, TcType) -> TcType
forall a b. (a, b) -> a
fst (TcType -> (TcType, TcType)
tcSplitFunTy TcType
ty)

tcFunResultTy :: Type -> Type
tcFunResultTy :: TcType -> TcType
tcFunResultTy TcType
ty = (TcType, TcType) -> TcType
forall a b. (a, b) -> b
snd (TcType -> (TcType, TcType)
tcSplitFunTy TcType
ty)

-- | Strips off n *visible* arguments and returns the resulting type
tcFunResultTyN :: HasDebugCallStack => Arity -> Type -> Type
tcFunResultTyN :: Int -> TcType -> TcType
tcFunResultTyN Int
n TcType
ty
  | Right ([TcType]
_, TcType
res_ty) <- Int -> TcType -> Either Int ([TcType], TcType)
tcSplitFunTysN Int
n TcType
ty
  = TcType
res_ty
  | Bool
otherwise
  = String -> SDoc -> TcType
forall a. HasCallStack => String -> SDoc -> a
pprPanic String
"tcFunResultTyN" (Int -> SDoc
forall a. Outputable a => a -> SDoc
ppr Int
n SDoc -> SDoc -> SDoc
<+> TcType -> SDoc
forall a. Outputable a => a -> SDoc
ppr TcType
ty)

-----------------------
tcSplitAppTy_maybe :: Type -> Maybe (Type, Type)
tcSplitAppTy_maybe :: TcType -> Maybe (TcType, TcType)
tcSplitAppTy_maybe TcType
ty | Just TcType
ty' <- TcType -> Maybe TcType
tcView TcType
ty = TcType -> Maybe (TcType, TcType)
tcSplitAppTy_maybe TcType
ty'
tcSplitAppTy_maybe TcType
ty = TcType -> Maybe (TcType, TcType)
tcRepSplitAppTy_maybe TcType
ty

tcSplitAppTy :: Type -> (Type, Type)
tcSplitAppTy :: TcType -> (TcType, TcType)
tcSplitAppTy TcType
ty = case TcType -> Maybe (TcType, TcType)
tcSplitAppTy_maybe TcType
ty of
                    Just (TcType, TcType)
stuff -> (TcType, TcType)
stuff
                    Maybe (TcType, TcType)
Nothing    -> String -> SDoc -> (TcType, TcType)
forall a. HasCallStack => String -> SDoc -> a
pprPanic String
"tcSplitAppTy" (TcType -> SDoc
pprType TcType
ty)

tcSplitAppTys :: Type -> (Type, [Type])
tcSplitAppTys :: TcType -> (TcType, [TcType])
tcSplitAppTys TcType
ty
  = TcType -> [TcType] -> (TcType, [TcType])
go TcType
ty []
  where
    go :: TcType -> [TcType] -> (TcType, [TcType])
go TcType
ty [TcType]
args = case TcType -> Maybe (TcType, TcType)
tcSplitAppTy_maybe TcType
ty of
                   Just (TcType
ty', TcType
arg) -> TcType -> [TcType] -> (TcType, [TcType])
go TcType
ty' (TcType
argTcType -> [TcType] -> [TcType]
forall a. a -> [a] -> [a]
:[TcType]
args)
                   Maybe (TcType, TcType)
Nothing         -> (TcType
ty,[TcType]
args)

-- | Returns the number of arguments in the given type, without
-- looking through synonyms. This is used only for error reporting.
-- We don't look through synonyms because of #11313.
tcRepGetNumAppTys :: Type -> Arity
tcRepGetNumAppTys :: TcType -> Int
tcRepGetNumAppTys = [TcType] -> Int
forall (t :: * -> *) a. Foldable t => t a -> Int
length ([TcType] -> Int) -> (TcType -> [TcType]) -> TcType -> Int
forall b c a. (b -> c) -> (a -> b) -> a -> c
. (TcType, [TcType]) -> [TcType]
forall a b. (a, b) -> b
snd ((TcType, [TcType]) -> [TcType])
-> (TcType -> (TcType, [TcType])) -> TcType -> [TcType]
forall b c a. (b -> c) -> (a -> b) -> a -> c
. HasDebugCallStack => TcType -> (TcType, [TcType])
TcType -> (TcType, [TcType])
repSplitAppTys

-----------------------
-- | If the type is a tyvar, possibly under a cast, returns it, along
-- with the coercion. Thus, the co is :: kind tv ~N kind type
tcGetCastedTyVar_maybe :: Type -> Maybe (TyVar, CoercionN)
tcGetCastedTyVar_maybe :: TcType -> Maybe (TcTyVar, KindCoercion)
tcGetCastedTyVar_maybe TcType
ty | Just TcType
ty' <- TcType -> Maybe TcType
tcView TcType
ty = TcType -> Maybe (TcTyVar, KindCoercion)
tcGetCastedTyVar_maybe TcType
ty'
tcGetCastedTyVar_maybe (CastTy (TyVarTy TcTyVar
tv) KindCoercion
co) = (TcTyVar, KindCoercion) -> Maybe (TcTyVar, KindCoercion)
forall a. a -> Maybe a
Just (TcTyVar
tv, KindCoercion
co)
tcGetCastedTyVar_maybe (TyVarTy TcTyVar
tv)             = (TcTyVar, KindCoercion) -> Maybe (TcTyVar, KindCoercion)
forall a. a -> Maybe a
Just (TcTyVar
tv, TcType -> KindCoercion
mkNomReflCo (TcTyVar -> TcType
tyVarKind TcTyVar
tv))
tcGetCastedTyVar_maybe TcType
_                        = Maybe (TcTyVar, KindCoercion)
forall a. Maybe a
Nothing

tcGetTyVar_maybe :: Type -> Maybe TyVar
tcGetTyVar_maybe :: TcType -> Maybe TcTyVar
tcGetTyVar_maybe TcType
ty | Just TcType
ty' <- TcType -> Maybe TcType
tcView TcType
ty = TcType -> Maybe TcTyVar
tcGetTyVar_maybe TcType
ty'
tcGetTyVar_maybe (TyVarTy TcTyVar
tv)   = TcTyVar -> Maybe TcTyVar
forall a. a -> Maybe a
Just TcTyVar
tv
tcGetTyVar_maybe TcType
_              = Maybe TcTyVar
forall a. Maybe a
Nothing

tcGetTyVar :: String -> Type -> TyVar
tcGetTyVar :: String -> TcType -> TcTyVar
tcGetTyVar String
msg TcType
ty
  = case TcType -> Maybe TcTyVar
tcGetTyVar_maybe TcType
ty of
     Just TcTyVar
tv -> TcTyVar
tv
     Maybe TcTyVar
Nothing -> String -> SDoc -> TcTyVar
forall a. HasCallStack => String -> SDoc -> a
pprPanic String
msg (TcType -> SDoc
forall a. Outputable a => a -> SDoc
ppr TcType
ty)

tcIsTyVarTy :: Type -> Bool
tcIsTyVarTy :: TcType -> Bool
tcIsTyVarTy TcType
ty | Just TcType
ty' <- TcType -> Maybe TcType
tcView TcType
ty = TcType -> Bool
tcIsTyVarTy TcType
ty'
tcIsTyVarTy (CastTy TcType
ty KindCoercion
_) = TcType -> Bool
tcIsTyVarTy TcType
ty  -- look through casts, as
                                            -- this is only used for
                                            -- e.g., FlexibleContexts
tcIsTyVarTy (TyVarTy TcTyVar
_)   = Bool
True
tcIsTyVarTy TcType
_             = Bool
False

-----------------------
tcSplitDFunTy :: Type -> ([TyVar], [Type], Class, [Type])
-- Split the type of a dictionary function
-- We don't use tcSplitSigmaTy,  because a DFun may (with NDP)
-- have non-Pred arguments, such as
--     df :: forall m. (forall b. Eq b => Eq (m b)) -> C m
--
-- Also NB splitFunTys, not tcSplitFunTys;
-- the latter specifically stops at PredTy arguments,
-- and we don't want to do that here
tcSplitDFunTy :: TcType -> ([TcTyVar], [TcType], Class, [TcType])
tcSplitDFunTy TcType
ty
  = case TcType -> ([TcTyVar], TcType)
tcSplitForAllTys TcType
ty   of { ([TcTyVar]
tvs, TcType
rho)    ->
    case TcType -> ([TcType], TcType)
splitFunTys TcType
rho       of { ([TcType]
theta, TcType
tau)  ->
    case TcType -> (Class, [TcType])
tcSplitDFunHead TcType
tau   of { (Class
clas, [TcType]
tys)   ->
    ([TcTyVar]
tvs, [TcType]
theta, Class
clas, [TcType]
tys) }}}

tcSplitDFunHead :: Type -> (Class, [Type])
tcSplitDFunHead :: TcType -> (Class, [TcType])
tcSplitDFunHead = HasDebugCallStack => TcType -> (Class, [TcType])
TcType -> (Class, [TcType])
getClassPredTys

tcSplitMethodTy :: Type -> ([TyVar], PredType, Type)
-- A class method (selector) always has a type like
--   forall as. C as => blah
-- So if the class looks like
--   class C a where
--     op :: forall b. (Eq a, Ix b) => a -> b
-- the class method type looks like
--  op :: forall a. C a => forall b. (Eq a, Ix b) => a -> b
--
-- tcSplitMethodTy just peels off the outer forall and
-- that first predicate
tcSplitMethodTy :: TcType -> ([TcTyVar], TcType, TcType)
tcSplitMethodTy TcType
ty
  | ([TcTyVar]
sel_tyvars,TcType
sel_rho) <- TcType -> ([TcTyVar], TcType)
tcSplitForAllTys TcType
ty
  , Just (TcType
first_pred, TcType
local_meth_ty) <- TcType -> Maybe (TcType, TcType)
tcSplitPredFunTy_maybe TcType
sel_rho
  = ([TcTyVar]
sel_tyvars, TcType
first_pred, TcType
local_meth_ty)
  | Bool
otherwise
  = String -> SDoc -> ([TcTyVar], TcType, TcType)
forall a. HasCallStack => String -> SDoc -> a
pprPanic String
"tcSplitMethodTy" (TcType -> SDoc
forall a. Outputable a => a -> SDoc
ppr TcType
ty)


{- *********************************************************************
*                                                                      *
            Type equalities
*                                                                      *
********************************************************************* -}

tcEqKind :: HasDebugCallStack => TcKind -> TcKind -> Bool
tcEqKind :: TcType -> TcType -> Bool
tcEqKind = HasDebugCallStack => TcType -> TcType -> Bool
TcType -> TcType -> Bool
tcEqType

tcEqType :: HasDebugCallStack => TcType -> TcType -> Bool
-- tcEqType is a proper implements the same Note [Non-trivial definitional
-- equality] (in TyCoRep) as `eqType`, but Type.eqType believes (* ==
-- Constraint), and that is NOT what we want in the type checker!
tcEqType :: TcType -> TcType -> Bool
tcEqType TcType
ty1 TcType
ty2
  =  Bool -> Bool -> TcType -> TcType -> Bool
tc_eq_type Bool
False Bool
False TcType
ki1 TcType
ki2
  Bool -> Bool -> Bool
&& Bool -> Bool -> TcType -> TcType -> Bool
tc_eq_type Bool
False Bool
False TcType
ty1 TcType
ty2
  where
    ki1 :: TcType
ki1 = HasDebugCallStack => TcType -> TcType
TcType -> TcType
tcTypeKind TcType
ty1
    ki2 :: TcType
ki2 = HasDebugCallStack => TcType -> TcType
TcType -> TcType
tcTypeKind TcType
ty2

-- | Just like 'tcEqType', but will return True for types of different kinds
-- as long as their non-coercion structure is identical.
tcEqTypeNoKindCheck :: TcType -> TcType -> Bool
tcEqTypeNoKindCheck :: TcType -> TcType -> Bool
tcEqTypeNoKindCheck TcType
ty1 TcType
ty2
  = Bool -> Bool -> TcType -> TcType -> Bool
tc_eq_type Bool
False Bool
False TcType
ty1 TcType
ty2

-- | Like 'tcEqType', but returns True if the /visible/ part of the types
-- are equal, even if they are really unequal (in the invisible bits)
tcEqTypeVis :: TcType -> TcType -> Bool
tcEqTypeVis :: TcType -> TcType -> Bool
tcEqTypeVis TcType
ty1 TcType
ty2 = Bool -> Bool -> TcType -> TcType -> Bool
tc_eq_type Bool
False Bool
True TcType
ty1 TcType
ty2

-- | Like 'pickyEqTypeVis', but returns a Bool for convenience
pickyEqType :: TcType -> TcType -> Bool
-- Check when two types _look_ the same, _including_ synonyms.
-- So (pickyEqType String [Char]) returns False
-- This ignores kinds and coercions, because this is used only for printing.
pickyEqType :: TcType -> TcType -> Bool
pickyEqType TcType
ty1 TcType
ty2 = Bool -> Bool -> TcType -> TcType -> Bool
tc_eq_type Bool
True Bool
False TcType
ty1 TcType
ty2



-- | Real worker for 'tcEqType'. No kind check!
tc_eq_type :: Bool          -- ^ True <=> do not expand type synonyms
           -> Bool          -- ^ True <=> compare visible args only
           -> Type -> Type
           -> Bool
-- Flags False, False is the usual setting for tc_eq_type
tc_eq_type :: Bool -> Bool -> TcType -> TcType -> Bool
tc_eq_type Bool
keep_syns Bool
vis_only TcType
orig_ty1 TcType
orig_ty2
  = RnEnv2 -> TcType -> TcType -> Bool
go RnEnv2
orig_env TcType
orig_ty1 TcType
orig_ty2
  where
    go :: RnEnv2 -> Type -> Type -> Bool
    go :: RnEnv2 -> TcType -> TcType -> Bool
go RnEnv2
env TcType
t1 TcType
t2 | Bool -> Bool
not Bool
keep_syns, Just TcType
t1' <- TcType -> Maybe TcType
tcView TcType
t1 = RnEnv2 -> TcType -> TcType -> Bool
go RnEnv2
env TcType
t1' TcType
t2
    go RnEnv2
env TcType
t1 TcType
t2 | Bool -> Bool
not Bool
keep_syns, Just TcType
t2' <- TcType -> Maybe TcType
tcView TcType
t2 = RnEnv2 -> TcType -> TcType -> Bool
go RnEnv2
env TcType
t1 TcType
t2'

    go RnEnv2
env (TyVarTy TcTyVar
tv1) (TyVarTy TcTyVar
tv2)
      = RnEnv2 -> TcTyVar -> TcTyVar
rnOccL RnEnv2
env TcTyVar
tv1 TcTyVar -> TcTyVar -> Bool
forall a. Eq a => a -> a -> Bool
== RnEnv2 -> TcTyVar -> TcTyVar
rnOccR RnEnv2
env TcTyVar
tv2

    go RnEnv2
_   (LitTy TyLit
lit1) (LitTy TyLit
lit2)
      = TyLit
lit1 TyLit -> TyLit -> Bool
forall a. Eq a => a -> a -> Bool
== TyLit
lit2

    go RnEnv2
env (ForAllTy (Bndr TcTyVar
tv1 ArgFlag
vis1) TcType
ty1)
           (ForAllTy (Bndr TcTyVar
tv2 ArgFlag
vis2) TcType
ty2)
      =  ArgFlag
vis1 ArgFlag -> ArgFlag -> Bool
forall a. Eq a => a -> a -> Bool
== ArgFlag
vis2
      Bool -> Bool -> Bool
&& (Bool
vis_only Bool -> Bool -> Bool
|| RnEnv2 -> TcType -> TcType -> Bool
go RnEnv2
env (TcTyVar -> TcType
varType TcTyVar
tv1) (TcTyVar -> TcType
varType TcTyVar
tv2))
      Bool -> Bool -> Bool
&& RnEnv2 -> TcType -> TcType -> Bool
go (RnEnv2 -> TcTyVar -> TcTyVar -> RnEnv2
rnBndr2 RnEnv2
env TcTyVar
tv1 TcTyVar
tv2) TcType
ty1 TcType
ty2

    -- Make sure we handle all FunTy cases since falling through to the
    -- AppTy case means that tcRepSplitAppTy_maybe may see an unzonked
    -- kind variable, which causes things to blow up.
    go RnEnv2
env (FunTy AnonArgFlag
_ TcType
arg1 TcType
res1) (FunTy AnonArgFlag
_ TcType
arg2 TcType
res2)
      = RnEnv2 -> TcType -> TcType -> Bool
go RnEnv2
env TcType
arg1 TcType
arg2 Bool -> Bool -> Bool
&& RnEnv2 -> TcType -> TcType -> Bool
go RnEnv2
env TcType
res1 TcType
res2
    go RnEnv2
env TcType
ty (FunTy AnonArgFlag
_ TcType
arg TcType
res) = RnEnv2 -> TcType -> TcType -> TcType -> Bool
eqFunTy RnEnv2
env TcType
arg TcType
res TcType
ty
    go RnEnv2
env (FunTy AnonArgFlag
_ TcType
arg TcType
res) TcType
ty = RnEnv2 -> TcType -> TcType -> TcType -> Bool
eqFunTy RnEnv2
env TcType
arg TcType
res TcType
ty

      -- See Note [Equality on AppTys] in Type
    go RnEnv2
env (AppTy TcType
s1 TcType
t1)        TcType
ty2
      | Just (TcType
s2, TcType
t2) <- TcType -> Maybe (TcType, TcType)
tcRepSplitAppTy_maybe TcType
ty2
      = RnEnv2 -> TcType -> TcType -> Bool
go RnEnv2
env TcType
s1 TcType
s2 Bool -> Bool -> Bool
&& RnEnv2 -> TcType -> TcType -> Bool
go RnEnv2
env TcType
t1 TcType
t2
    go RnEnv2
env TcType
ty1                  (AppTy TcType
s2 TcType
t2)
      | Just (TcType
s1, TcType
t1) <- TcType -> Maybe (TcType, TcType)
tcRepSplitAppTy_maybe TcType
ty1
      = RnEnv2 -> TcType -> TcType -> Bool
go RnEnv2
env TcType
s1 TcType
s2 Bool -> Bool -> Bool
&& RnEnv2 -> TcType -> TcType -> Bool
go RnEnv2
env TcType
t1 TcType
t2

    go RnEnv2
env (TyConApp TyCon
tc1 [TcType]
ts1)   (TyConApp TyCon
tc2 [TcType]
ts2)
      = TyCon
tc1 TyCon -> TyCon -> Bool
forall a. Eq a => a -> a -> Bool
== TyCon
tc2 Bool -> Bool -> Bool
&& RnEnv2 -> [Bool] -> [TcType] -> [TcType] -> Bool
gos RnEnv2
env (TyCon -> [Bool]
tc_vis TyCon
tc1) [TcType]
ts1 [TcType]
ts2

    go RnEnv2
env (CastTy TcType
t1 KindCoercion
_)   TcType
t2              = RnEnv2 -> TcType -> TcType -> Bool
go RnEnv2
env TcType
t1 TcType
t2
    go RnEnv2
env TcType
t1              (CastTy TcType
t2 KindCoercion
_)   = RnEnv2 -> TcType -> TcType -> Bool
go RnEnv2
env TcType
t1 TcType
t2
    go RnEnv2
_   (CoercionTy {}) (CoercionTy {}) = Bool
True

    go RnEnv2
_ TcType
_ TcType
_ = Bool
False

    gos :: RnEnv2 -> [Bool] -> [TcType] -> [TcType] -> Bool
gos RnEnv2
_   [Bool]
_         []       []      = Bool
True
    gos RnEnv2
env (Bool
ig:[Bool]
igs) (TcType
t1:[TcType]
ts1) (TcType
t2:[TcType]
ts2) = (Bool
ig Bool -> Bool -> Bool
|| RnEnv2 -> TcType -> TcType -> Bool
go RnEnv2
env TcType
t1 TcType
t2)
                                      Bool -> Bool -> Bool
&& RnEnv2 -> [Bool] -> [TcType] -> [TcType] -> Bool
gos RnEnv2
env [Bool]
igs [TcType]
ts1 [TcType]
ts2
    gos RnEnv2
_ [Bool]
_ [TcType]
_ [TcType]
_ = Bool
False

    tc_vis :: TyCon -> [Bool]  -- True for the fields we should ignore
    tc_vis :: TyCon -> [Bool]
tc_vis TyCon
tc | Bool
vis_only  = [Bool]
inviss [Bool] -> [Bool] -> [Bool]
forall a. [a] -> [a] -> [a]
++ Bool -> [Bool]
forall a. a -> [a]
repeat Bool
False    -- Ignore invisibles
              | Bool
otherwise = Bool -> [Bool]
forall a. a -> [a]
repeat Bool
False              -- Ignore nothing
       -- The repeat False is necessary because tycons
       -- can legitimately be oversaturated
      where
        bndrs :: [TyConBinder]
bndrs = TyCon -> [TyConBinder]
tyConBinders TyCon
tc
        inviss :: [Bool]
inviss  = (TyConBinder -> Bool) -> [TyConBinder] -> [Bool]
forall a b. (a -> b) -> [a] -> [b]
map TyConBinder -> Bool
forall tv. VarBndr tv TyConBndrVis -> Bool
isInvisibleTyConBinder [TyConBinder]
bndrs

    orig_env :: RnEnv2
orig_env = InScopeSet -> RnEnv2
mkRnEnv2 (InScopeSet -> RnEnv2) -> InScopeSet -> RnEnv2
forall a b. (a -> b) -> a -> b
$ VarSet -> InScopeSet
mkInScopeSet (VarSet -> InScopeSet) -> VarSet -> InScopeSet
forall a b. (a -> b) -> a -> b
$ [TcType] -> VarSet
tyCoVarsOfTypes [TcType
orig_ty1, TcType
orig_ty2]

    -- @eqFunTy arg res ty@ is True when @ty@ equals @FunTy arg res@. This is
    -- sometimes hard to know directly because @ty@ might have some casts
    -- obscuring the FunTy. And 'splitAppTy' is difficult because we can't
    -- always extract a RuntimeRep (see Note [xyz]) if the kind of the arg or
    -- res is unzonked/unflattened. Thus this function, which handles this
    -- corner case.
    eqFunTy :: RnEnv2 -> Type -> Type -> Type -> Bool
               -- Last arg is /not/ FunTy
    eqFunTy :: RnEnv2 -> TcType -> TcType -> TcType -> Bool
eqFunTy RnEnv2
env TcType
arg TcType
res ty :: TcType
ty@(AppTy{}) = TcType -> [TcType] -> Bool
get_args TcType
ty []
      where
        get_args :: Type -> [Type] -> Bool
        get_args :: TcType -> [TcType] -> Bool
get_args (AppTy TcType
f TcType
x)       [TcType]
args = TcType -> [TcType] -> Bool
get_args TcType
f (TcType
xTcType -> [TcType] -> [TcType]
forall a. a -> [a] -> [a]
:[TcType]
args)
        get_args (CastTy TcType
t KindCoercion
_)      [TcType]
args = TcType -> [TcType] -> Bool
get_args TcType
t [TcType]
args
        get_args (TyConApp TyCon
tc [TcType]
tys) [TcType]
args
          | TyCon
tc TyCon -> TyCon -> Bool
forall a. Eq a => a -> a -> Bool
== TyCon
funTyCon
          , [TcType
_, TcType
_, TcType
arg', TcType
res'] <- [TcType]
tys [TcType] -> [TcType] -> [TcType]
forall a. [a] -> [a] -> [a]
++ [TcType]
args
          = RnEnv2 -> TcType -> TcType -> Bool
go RnEnv2
env TcType
arg TcType
arg' Bool -> Bool -> Bool
&& RnEnv2 -> TcType -> TcType -> Bool
go RnEnv2
env TcType
res TcType
res'
        get_args TcType
_ [TcType]
_    = Bool
False
    eqFunTy RnEnv2
_ TcType
_ TcType
_ TcType
_     = Bool
False

{- *********************************************************************
*                                                                      *
                       Predicate types
*                                                                      *
************************************************************************

Deconstructors and tests on predicate types

Note [Kind polymorphic type classes]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    class C f where...   -- C :: forall k. k -> Constraint
    g :: forall (f::*). C f => f -> f

Here the (C f) in the signature is really (C * f), and we
don't want to complain that the * isn't a type variable!
-}

isTyVarClassPred :: PredType -> Bool
isTyVarClassPred :: TcType -> Bool
isTyVarClassPred TcType
ty = case TcType -> Maybe (Class, [TcType])
getClassPredTys_maybe TcType
ty of
    Just (Class
_, [TcType]
tys) -> (TcType -> Bool) -> [TcType] -> Bool
forall (t :: * -> *) a. Foldable t => (a -> Bool) -> t a -> Bool
all TcType -> Bool
isTyVarTy [TcType]
tys
    Maybe (Class, [TcType])
_             -> Bool
False

-------------------------
checkValidClsArgs :: Bool -> Class -> [KindOrType] -> Bool
-- If the Bool is True (flexible contexts), return True (i.e. ok)
-- Otherwise, check that the type (not kind) args are all headed by a tyvar
--   E.g. (Eq a) accepted, (Eq (f a)) accepted, but (Eq Int) rejected
-- This function is here rather than in TcValidity because it is
-- called from TcSimplify, which itself is imported by TcValidity
checkValidClsArgs :: Bool -> Class -> [TcType] -> Bool
checkValidClsArgs Bool
flexible_contexts Class
cls [TcType]
kts
  | Bool
flexible_contexts = Bool
True
  | Bool
otherwise         = (TcType -> Bool) -> [TcType] -> Bool
forall (t :: * -> *) a. Foldable t => (a -> Bool) -> t a -> Bool
all TcType -> Bool
hasTyVarHead [TcType]
tys
  where
    tys :: [TcType]
tys = TyCon -> [TcType] -> [TcType]
filterOutInvisibleTypes (Class -> TyCon
classTyCon Class
cls) [TcType]
kts

hasTyVarHead :: Type -> Bool
-- Returns true of (a t1 .. tn), where 'a' is a type variable
hasTyVarHead :: TcType -> Bool
hasTyVarHead TcType
ty                 -- Haskell 98 allows predicates of form
  | TcType -> Bool
tcIsTyVarTy TcType
ty = Bool
True       --      C (a ty1 .. tyn)
  | Bool
otherwise                   -- where a is a type variable
  = case TcType -> Maybe (TcType, TcType)
tcSplitAppTy_maybe TcType
ty of
       Just (TcType
ty, TcType
_) -> TcType -> Bool
hasTyVarHead TcType
ty
       Maybe (TcType, TcType)
Nothing      -> Bool
False

evVarPred :: EvVar -> PredType
evVarPred :: TcTyVar -> TcType
evVarPred TcTyVar
var = TcTyVar -> TcType
varType TcTyVar
var
  -- Historical note: I used to have an ASSERT here,
  -- checking (isEvVarType (varType var)).  But with something like
  --   f :: c => _ -> _
  -- we end up with (c :: kappa), and (kappa ~ Constraint).  Until
  -- we solve and zonk (which there is no particular reason to do for
  -- partial signatures, (isEvVarType kappa) will return False. But
  -- nothing is wrong.  So I just removed the ASSERT.

------------------
-- | When inferring types, should we quantify over a given predicate?
-- Generally true of classes; generally false of equality constraints.
-- Equality constraints that mention quantified type variables and
-- implicit variables complicate the story. See Notes
-- [Inheriting implicit parameters] and [Quantifying over equality constraints]
pickQuantifiablePreds
  :: TyVarSet           -- Quantifying over these
  -> TcThetaType        -- Proposed constraints to quantify
  -> TcThetaType        -- A subset that we can actually quantify
-- This function decides whether a particular constraint should be
-- quantified over, given the type variables that are being quantified
pickQuantifiablePreds :: VarSet -> [TcType] -> [TcType]
pickQuantifiablePreds VarSet
qtvs [TcType]
theta
  = let flex_ctxt :: Bool
flex_ctxt = Bool
True in  -- Quantify over non-tyvar constraints, even without
                             -- -XFlexibleContexts: see #10608, #10351
         -- flex_ctxt <- xoptM Opt_FlexibleContexts
    (TcType -> Maybe TcType) -> [TcType] -> [TcType]
forall a b. (a -> Maybe b) -> [a] -> [b]
mapMaybe (Bool -> TcType -> Maybe TcType
pick_me Bool
flex_ctxt) [TcType]
theta
  where
    pick_me :: Bool -> TcType -> Maybe TcType
pick_me Bool
flex_ctxt TcType
pred
      = case TcType -> Pred
classifyPredType TcType
pred of

          ClassPred Class
cls [TcType]
tys
            | Just {} <- Class -> [TcType] -> Maybe FastString
isCallStackPred Class
cls [TcType]
tys
              -- NEVER infer a CallStack constraint.  Otherwise we let
              -- the constraints bubble up to be solved from the outer
              -- context, or be defaulted when we reach the top-level.
              -- See Note [Overview of implicit CallStacks]
            -> Maybe TcType
forall a. Maybe a
Nothing

            | Class -> Bool
isIPClass Class
cls
            -> TcType -> Maybe TcType
forall a. a -> Maybe a
Just TcType
pred -- See note [Inheriting implicit parameters]

            | Bool -> Class -> [TcType] -> Bool
pick_cls_pred Bool
flex_ctxt Class
cls [TcType]
tys
            -> TcType -> Maybe TcType
forall a. a -> Maybe a
Just TcType
pred

          EqPred EqRel
eq_rel TcType
ty1 TcType
ty2
            | EqRel -> TcType -> TcType -> Bool
quantify_equality EqRel
eq_rel TcType
ty1 TcType
ty2
            , Just (Class
cls, [TcType]
tys) <- EqRel -> TcType -> TcType -> Maybe (Class, [TcType])
boxEqPred EqRel
eq_rel TcType
ty1 TcType
ty2
              -- boxEqPred: See Note [Lift equality constaints when quantifying]
            , Bool -> Class -> [TcType] -> Bool
pick_cls_pred Bool
flex_ctxt Class
cls [TcType]
tys
            -> TcType -> Maybe TcType
forall a. a -> Maybe a
Just (Class -> [TcType] -> TcType
mkClassPred Class
cls [TcType]
tys)

          IrredPred TcType
ty
            | TcType -> VarSet
tyCoVarsOfType TcType
ty VarSet -> VarSet -> Bool
`intersectsVarSet` VarSet
qtvs
            -> TcType -> Maybe TcType
forall a. a -> Maybe a
Just TcType
pred

          Pred
_ -> Maybe TcType
forall a. Maybe a
Nothing


    pick_cls_pred :: Bool -> Class -> [TcType] -> Bool
pick_cls_pred Bool
flex_ctxt Class
cls [TcType]
tys
      = [TcType] -> VarSet
tyCoVarsOfTypes [TcType]
tys VarSet -> VarSet -> Bool
`intersectsVarSet` VarSet
qtvs
        Bool -> Bool -> Bool
&& (Bool -> Class -> [TcType] -> Bool
checkValidClsArgs Bool
flex_ctxt Class
cls [TcType]
tys)
           -- Only quantify over predicates that checkValidType
           -- will pass!  See #10351.

    -- See Note [Quantifying over equality constraints]
    quantify_equality :: EqRel -> TcType -> TcType -> Bool
quantify_equality EqRel
NomEq  TcType
ty1 TcType
ty2 = TcType -> Bool
quant_fun TcType
ty1 Bool -> Bool -> Bool
|| TcType -> Bool
quant_fun TcType
ty2
    quantify_equality EqRel
ReprEq TcType
_   TcType
_   = Bool
True

    quant_fun :: TcType -> Bool
quant_fun TcType
ty
      = case HasCallStack => TcType -> Maybe (TyCon, [TcType])
TcType -> Maybe (TyCon, [TcType])
tcSplitTyConApp_maybe TcType
ty of
          Just (TyCon
tc, [TcType]
tys) | TyCon -> Bool
isTypeFamilyTyCon TyCon
tc
                         -> [TcType] -> VarSet
tyCoVarsOfTypes [TcType]
tys VarSet -> VarSet -> Bool
`intersectsVarSet` VarSet
qtvs
          Maybe (TyCon, [TcType])
_ -> Bool
False

boxEqPred :: EqRel -> Type -> Type -> Maybe (Class, [Type])
-- Given (t1 ~# t2) or (t1 ~R# t2) return the boxed version
--       (t1 ~ t2)  or (t1 `Coercible` t2)
boxEqPred :: EqRel -> TcType -> TcType -> Maybe (Class, [TcType])
boxEqPred EqRel
eq_rel TcType
ty1 TcType
ty2
  = case EqRel
eq_rel of
      EqRel
NomEq  | Bool
homo_kind -> (Class, [TcType]) -> Maybe (Class, [TcType])
forall a. a -> Maybe a
Just (Class
eqClass,        [TcType
k1,     TcType
ty1, TcType
ty2])
             | Bool
otherwise -> (Class, [TcType]) -> Maybe (Class, [TcType])
forall a. a -> Maybe a
Just (Class
heqClass,       [TcType
k1, TcType
k2, TcType
ty1, TcType
ty2])
      EqRel
ReprEq | Bool
homo_kind -> (Class, [TcType]) -> Maybe (Class, [TcType])
forall a. a -> Maybe a
Just (Class
coercibleClass, [TcType
k1,     TcType
ty1, TcType
ty2])
             | Bool
otherwise -> Maybe (Class, [TcType])
forall a. Maybe a
Nothing -- Sigh: we do not have hererogeneous Coercible
                                    --       so we can't abstract over it
                                    -- Nothing fundamental: we could add it
 where
   k1 :: TcType
k1 = HasDebugCallStack => TcType -> TcType
TcType -> TcType
tcTypeKind TcType
ty1
   k2 :: TcType
k2 = HasDebugCallStack => TcType -> TcType
TcType -> TcType
tcTypeKind TcType
ty2
   homo_kind :: Bool
homo_kind = TcType
k1 HasDebugCallStack => TcType -> TcType -> Bool
TcType -> TcType -> Bool
`tcEqType` TcType
k2

pickCapturedPreds
  :: TyVarSet           -- Quantifying over these
  -> TcThetaType        -- Proposed constraints to quantify
  -> TcThetaType        -- A subset that we can actually quantify
-- A simpler version of pickQuantifiablePreds, used to winnow down
-- the inferred constraints of a group of bindings, into those for
-- one particular identifier
pickCapturedPreds :: VarSet -> [TcType] -> [TcType]
pickCapturedPreds VarSet
qtvs [TcType]
theta
  = (TcType -> Bool) -> [TcType] -> [TcType]
forall a. (a -> Bool) -> [a] -> [a]
filter TcType -> Bool
captured [TcType]
theta
  where
    captured :: TcType -> Bool
captured TcType
pred = TcType -> Bool
isIPPred TcType
pred Bool -> Bool -> Bool
|| (TcType -> VarSet
tyCoVarsOfType TcType
pred VarSet -> VarSet -> Bool
`intersectsVarSet` VarSet
qtvs)


-- Superclasses

type PredWithSCs a = (PredType, [PredType], a)

mkMinimalBySCs :: forall a. (a -> PredType) -> [a] -> [a]
-- Remove predicates that
--
--   - are the same as another predicate
--
--   - can be deduced from another by superclasses,
--
--   - are a reflexive equality (e.g  * ~ *)
--     (see Note [Remove redundant provided dicts] in TcPatSyn)
--
-- The result is a subset of the input.
-- The 'a' is just paired up with the PredType;
--   typically it might be a dictionary Id
mkMinimalBySCs :: (a -> TcType) -> [a] -> [a]
mkMinimalBySCs a -> TcType
get_pred [a]
xs = [PredWithSCs a] -> [PredWithSCs a] -> [a]
go [PredWithSCs a]
preds_with_scs []
 where
   preds_with_scs :: [PredWithSCs a]
   preds_with_scs :: [PredWithSCs a]
preds_with_scs = [ (TcType
pred, TcType
pred TcType -> [TcType] -> [TcType]
forall a. a -> [a] -> [a]
: TcType -> [TcType]
transSuperClasses TcType
pred, a
x)
                    | a
x <- [a]
xs
                    , let pred :: TcType
pred = a -> TcType
get_pred a
x ]

   go :: [PredWithSCs a]   -- Work list
      -> [PredWithSCs a]   -- Accumulating result
      -> [a]
   go :: [PredWithSCs a] -> [PredWithSCs a] -> [a]
go [] [PredWithSCs a]
min_preds
     = [a] -> [a]
forall a. [a] -> [a]
reverse ((PredWithSCs a -> a) -> [PredWithSCs a] -> [a]
forall a b. (a -> b) -> [a] -> [b]
map PredWithSCs a -> a
forall a b c. (a, b, c) -> c
thdOf3 [PredWithSCs a]
min_preds)
       -- The 'reverse' isn't strictly necessary, but it
       -- means that the results are returned in the same
       -- order as the input, which is generally saner
   go (work_item :: PredWithSCs a
work_item@(TcType
p,[TcType]
_,a
_) : [PredWithSCs a]
work_list) [PredWithSCs a]
min_preds
     | EqPred EqRel
_ TcType
t1 TcType
t2 <- TcType -> Pred
classifyPredType TcType
p
     , TcType
t1 HasDebugCallStack => TcType -> TcType -> Bool
TcType -> TcType -> Bool
`tcEqType` TcType
t2   -- See TcPatSyn
                          -- Note [Remove redundant provided dicts]
     = [PredWithSCs a] -> [PredWithSCs a] -> [a]
go [PredWithSCs a]
work_list [PredWithSCs a]
min_preds
     | TcType
p TcType -> [PredWithSCs a] -> Bool
`in_cloud` [PredWithSCs a]
work_list Bool -> Bool -> Bool
|| TcType
p TcType -> [PredWithSCs a] -> Bool
`in_cloud` [PredWithSCs a]
min_preds
     = [PredWithSCs a] -> [PredWithSCs a] -> [a]
go [PredWithSCs a]
work_list [PredWithSCs a]
min_preds
     | Bool
otherwise
     = [PredWithSCs a] -> [PredWithSCs a] -> [a]
go [PredWithSCs a]
work_list (PredWithSCs a
work_item PredWithSCs a -> [PredWithSCs a] -> [PredWithSCs a]
forall a. a -> [a] -> [a]
: [PredWithSCs a]
min_preds)

   in_cloud :: PredType -> [PredWithSCs a] -> Bool
   in_cloud :: TcType -> [PredWithSCs a] -> Bool
in_cloud TcType
p [PredWithSCs a]
ps = [Bool] -> Bool
forall (t :: * -> *). Foldable t => t Bool -> Bool
or [ TcType
p HasDebugCallStack => TcType -> TcType -> Bool
TcType -> TcType -> Bool
`tcEqType` TcType
p' | (TcType
_, [TcType]
scs, a
_) <- [PredWithSCs a]
ps, TcType
p' <- [TcType]
scs ]

transSuperClasses :: PredType -> [PredType]
-- (transSuperClasses p) returns (p's superclasses) not including p
-- Stop if you encounter the same class again
-- See Note [Expanding superclasses]
transSuperClasses :: TcType -> [TcType]
transSuperClasses TcType
p
  = NameSet -> TcType -> [TcType]
go NameSet
emptyNameSet TcType
p
  where
    go :: NameSet -> PredType -> [PredType]
    go :: NameSet -> TcType -> [TcType]
go NameSet
rec_clss TcType
p
       | ClassPred Class
cls [TcType]
tys <- TcType -> Pred
classifyPredType TcType
p
       , let cls_nm :: Name
cls_nm = Class -> Name
className Class
cls
       , Bool -> Bool
not (Name
cls_nm Name -> NameSet -> Bool
`elemNameSet` NameSet
rec_clss)
       , let rec_clss' :: NameSet
rec_clss' | Class -> Bool
isCTupleClass Class
cls = NameSet
rec_clss
                       | Bool
otherwise         = NameSet
rec_clss NameSet -> Name -> NameSet
`extendNameSet` Name
cls_nm
       = [ TcType
p' | TcType
sc <- Class -> [TcType] -> [TcType]
immSuperClasses Class
cls [TcType]
tys
              , TcType
p'  <- TcType
sc TcType -> [TcType] -> [TcType]
forall a. a -> [a] -> [a]
: NameSet -> TcType -> [TcType]
go NameSet
rec_clss' TcType
sc ]
       | Bool
otherwise
       = []

immSuperClasses :: Class -> [Type] -> [PredType]
immSuperClasses :: Class -> [TcType] -> [TcType]
immSuperClasses Class
cls [TcType]
tys
  = HasCallStack => TCvSubst -> [TcType] -> [TcType]
TCvSubst -> [TcType] -> [TcType]
substTheta ([TcTyVar] -> [TcType] -> TCvSubst
HasDebugCallStack => [TcTyVar] -> [TcType] -> TCvSubst
zipTvSubst [TcTyVar]
tyvars [TcType]
tys) [TcType]
sc_theta
  where
    ([TcTyVar]
tyvars,[TcType]
sc_theta,[TcTyVar]
_,[ClassOpItem]
_) = Class -> ([TcTyVar], [TcType], [TcTyVar], [ClassOpItem])
classBigSig Class
cls

isImprovementPred :: PredType -> Bool
-- Either it's an equality, or has some functional dependency
isImprovementPred :: TcType -> Bool
isImprovementPred TcType
ty
  = case TcType -> Pred
classifyPredType TcType
ty of
      EqPred EqRel
NomEq TcType
t1 TcType
t2 -> Bool -> Bool
not (TcType
t1 HasDebugCallStack => TcType -> TcType -> Bool
TcType -> TcType -> Bool
`tcEqType` TcType
t2)
      EqPred EqRel
ReprEq TcType
_ TcType
_  -> Bool
False
      ClassPred Class
cls [TcType]
_    -> Class -> Bool
classHasFds Class
cls
      IrredPred {}       -> Bool
True -- Might have equalities after reduction?
      ForAllPred {}      -> Bool
False

-- | Is the equality
--        a ~r ...a....
-- definitely insoluble or not?
--      a ~r Maybe a      -- Definitely insoluble
--      a ~N ...(F a)...  -- Not definitely insoluble
--                        -- Perhaps (F a) reduces to Int
--      a ~R ...(N a)...  -- Not definitely insoluble
--                        -- Perhaps newtype N a = MkN Int
-- See Note [Occurs check error] in
-- TcCanonical for the motivation for this function.
isInsolubleOccursCheck :: EqRel -> TcTyVar -> TcType -> Bool
isInsolubleOccursCheck :: EqRel -> TcTyVar -> TcType -> Bool
isInsolubleOccursCheck EqRel
eq_rel TcTyVar
tv TcType
ty
  = TcType -> Bool
go TcType
ty
  where
    go :: TcType -> Bool
go TcType
ty | Just TcType
ty' <- TcType -> Maybe TcType
tcView TcType
ty = TcType -> Bool
go TcType
ty'
    go (TyVarTy TcTyVar
tv') = TcTyVar
tv TcTyVar -> TcTyVar -> Bool
forall a. Eq a => a -> a -> Bool
== TcTyVar
tv' Bool -> Bool -> Bool
|| TcType -> Bool
go (TcTyVar -> TcType
tyVarKind TcTyVar
tv')
    go (LitTy {})    = Bool
False
    go (AppTy TcType
t1 TcType
t2) = case EqRel
eq_rel of  -- See Note [AppTy and ReprEq]
                         EqRel
NomEq  -> TcType -> Bool
go TcType
t1 Bool -> Bool -> Bool
|| TcType -> Bool
go TcType
t2
                         EqRel
ReprEq -> TcType -> Bool
go TcType
t1
    go (FunTy AnonArgFlag
_ TcType
t1 TcType
t2) = TcType -> Bool
go TcType
t1 Bool -> Bool -> Bool
|| TcType -> Bool
go TcType
t2
    go (ForAllTy (Bndr TcTyVar
tv' ArgFlag
_) TcType
inner_ty)
      | TcTyVar
tv' TcTyVar -> TcTyVar -> Bool
forall a. Eq a => a -> a -> Bool
== TcTyVar
tv = Bool
False
      | Bool
otherwise = TcType -> Bool
go (TcTyVar -> TcType
varType TcTyVar
tv') Bool -> Bool -> Bool
|| TcType -> Bool
go TcType
inner_ty
    go (CastTy TcType
ty KindCoercion
_)  = TcType -> Bool
go TcType
ty   -- ToDo: what about the coercion
    go (CoercionTy KindCoercion
_) = Bool
False   -- ToDo: what about the coercion
    go (TyConApp TyCon
tc [TcType]
tys)
      | TyCon -> Role -> Bool
isGenerativeTyCon TyCon
tc Role
role = (TcType -> Bool) -> [TcType] -> Bool
forall (t :: * -> *) a. Foldable t => (a -> Bool) -> t a -> Bool
any TcType -> Bool
go [TcType]
tys
      | Bool
otherwise                 = (TcType -> Bool) -> [TcType] -> Bool
forall (t :: * -> *) a. Foldable t => (a -> Bool) -> t a -> Bool
any TcType -> Bool
go (Int -> [TcType] -> [TcType]
forall a. Int -> [a] -> [a]
drop (TyCon -> Int
tyConArity TyCon
tc) [TcType]
tys)
         -- (a ~ F b a), where F has arity 1,
         -- has an insoluble occurs check

    role :: Role
role = EqRel -> Role
eqRelRole EqRel
eq_rel

{- Note [Expanding superclasses]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
When we expand superclasses, we use the following algorithm:

transSuperClasses( C tys ) returns the transitive superclasses
                           of (C tys), not including C itself

For example
  class C a b => D a b
  class D b a => C a b

Then
  transSuperClasses( Ord ty )  = [Eq ty]
  transSuperClasses( C ta tb ) = [D tb ta, C tb ta]

Notice that in the recursive-superclass case we include C again at
the end of the chain.  One could exclude C in this case, but
the code is more awkward and there seems no good reason to do so.
(However C.f. TcCanonical.mk_strict_superclasses, which /does/
appear to do so.)

The algorithm is expand( so_far, pred ):

 1. If pred is not a class constraint, return empty set
       Otherwise pred = C ts
 2. If C is in so_far, return empty set (breaks loops)
 3. Find the immediate superclasses constraints of (C ts)
 4. For each such sc_pred, return (sc_pred : expand( so_far+C, D ss )

Notice that

 * With normal Haskell-98 classes, the loop-detector will never bite,
   so we'll get all the superclasses.

 * We need the loop-breaker in case we have UndecidableSuperClasses on

 * Since there is only a finite number of distinct classes, expansion
   must terminate.

 * The loop breaking is a bit conservative. Notably, a tuple class
   could contain many times without threatening termination:
      (Eq a, (Ord a, Ix a))
   And this is try of any class that we can statically guarantee
   as non-recursive (in some sense).  For now, we just make a special
   case for tuples.  Something better would be cool.

See also TcTyDecls.checkClassCycles.

Note [Lift equality constaints when quantifying]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
We can't quantify over a constraint (t1 ~# t2) because that isn't a
predicate type; see Note [Types for coercions, predicates, and evidence]
in TyCoRep.

So we have to 'lift' it to (t1 ~ t2).  Similarly (~R#) must be lifted
to Coercible.

This tiresome lifting is the reason that pick_me (in
pickQuantifiablePreds) returns a Maybe rather than a Bool.

Note [Quantifying over equality constraints]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Should we quantify over an equality constraint (s ~ t)?  In general, we don't.
Doing so may simply postpone a type error from the function definition site to
its call site.  (At worst, imagine (Int ~ Bool)).

However, consider this
         forall a. (F [a] ~ Int) => blah
Should we quantify over the (F [a] ~ Int)?  Perhaps yes, because at the call
site we will know 'a', and perhaps we have instance  F [Bool] = Int.
So we *do* quantify over a type-family equality where the arguments mention
the quantified variables.

Note [Inheriting implicit parameters]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Consider this:

        f x = (x::Int) + ?y

where f is *not* a top-level binding.
From the RHS of f we'll get the constraint (?y::Int).
There are two types we might infer for f:

        f :: Int -> Int

(so we get ?y from the context of f's definition), or

        f :: (?y::Int) => Int -> Int

At first you might think the first was better, because then
?y behaves like a free variable of the definition, rather than
having to be passed at each call site.  But of course, the WHOLE
IDEA is that ?y should be passed at each call site (that's what
dynamic binding means) so we'd better infer the second.

BOTTOM LINE: when *inferring types* you must quantify over implicit
parameters, *even if* they don't mention the bound type variables.
Reason: because implicit parameters, uniquely, have local instance
declarations. See pickQuantifiablePreds.

Note [Quantifying over equality constraints]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Should we quantify over an equality constraint (s ~ t)?  In general, we don't.
Doing so may simply postpone a type error from the function definition site to
its call site.  (At worst, imagine (Int ~ Bool)).

However, consider this
         forall a. (F [a] ~ Int) => blah
Should we quantify over the (F [a] ~ Int).  Perhaps yes, because at the call
site we will know 'a', and perhaps we have instance  F [Bool] = Int.
So we *do* quantify over a type-family equality where the arguments mention
the quantified variables.

************************************************************************
*                                                                      *
      Classifying types
*                                                                      *
************************************************************************
-}

isSigmaTy :: TcType -> Bool
-- isSigmaTy returns true of any qualified type.  It doesn't
-- *necessarily* have any foralls.  E.g
--        f :: (?x::Int) => Int -> Int
isSigmaTy :: TcType -> Bool
isSigmaTy TcType
ty | Just TcType
ty' <- TcType -> Maybe TcType
tcView TcType
ty = TcType -> Bool
isSigmaTy TcType
ty'
isSigmaTy (ForAllTy {})                = Bool
True
isSigmaTy (FunTy { ft_af :: TcType -> AnonArgFlag
ft_af = AnonArgFlag
InvisArg }) = Bool
True
isSigmaTy TcType
_                            = Bool
False

isRhoTy :: TcType -> Bool   -- True of TcRhoTypes; see Note [TcRhoType]
isRhoTy :: TcType -> Bool
isRhoTy TcType
ty | Just TcType
ty' <- TcType -> Maybe TcType
tcView TcType
ty = TcType -> Bool
isRhoTy TcType
ty'
isRhoTy (ForAllTy {})                          = Bool
False
isRhoTy (FunTy { ft_af :: TcType -> AnonArgFlag
ft_af = AnonArgFlag
VisArg, ft_res :: TcType -> TcType
ft_res = TcType
r }) = TcType -> Bool
isRhoTy TcType
r
isRhoTy TcType
_                                      = Bool
True

-- | Like 'isRhoTy', but also says 'True' for 'Infer' types
isRhoExpTy :: ExpType -> Bool
isRhoExpTy :: ExpType -> Bool
isRhoExpTy (Check TcType
ty) = TcType -> Bool
isRhoTy TcType
ty
isRhoExpTy (Infer {}) = Bool
True

isOverloadedTy :: Type -> Bool
-- Yes for a type of a function that might require evidence-passing
-- Used only by bindLocalMethods
isOverloadedTy :: TcType -> Bool
isOverloadedTy TcType
ty | Just TcType
ty' <- TcType -> Maybe TcType
tcView TcType
ty = TcType -> Bool
isOverloadedTy TcType
ty'
isOverloadedTy (ForAllTy TyCoVarBinder
_  TcType
ty)             = TcType -> Bool
isOverloadedTy TcType
ty
isOverloadedTy (FunTy { ft_af :: TcType -> AnonArgFlag
ft_af = AnonArgFlag
InvisArg }) = Bool
True
isOverloadedTy TcType
_                            = Bool
False

isFloatTy, isDoubleTy, isIntegerTy, isIntTy, isWordTy, isBoolTy,
    isUnitTy, isCharTy, isAnyTy :: Type -> Bool
isFloatTy :: TcType -> Bool
isFloatTy      = Unique -> TcType -> Bool
is_tc Unique
floatTyConKey
isDoubleTy :: TcType -> Bool
isDoubleTy     = Unique -> TcType -> Bool
is_tc Unique
doubleTyConKey
isIntegerTy :: TcType -> Bool
isIntegerTy    = Unique -> TcType -> Bool
is_tc Unique
integerTyConKey
isIntTy :: TcType -> Bool
isIntTy        = Unique -> TcType -> Bool
is_tc Unique
intTyConKey
isWordTy :: TcType -> Bool
isWordTy       = Unique -> TcType -> Bool
is_tc Unique
wordTyConKey
isBoolTy :: TcType -> Bool
isBoolTy       = Unique -> TcType -> Bool
is_tc Unique
boolTyConKey
isUnitTy :: TcType -> Bool
isUnitTy       = Unique -> TcType -> Bool
is_tc Unique
unitTyConKey
isCharTy :: TcType -> Bool
isCharTy       = Unique -> TcType -> Bool
is_tc Unique
charTyConKey
isAnyTy :: TcType -> Bool
isAnyTy        = Unique -> TcType -> Bool
is_tc Unique
anyTyConKey

-- | Does a type represent a floating-point number?
isFloatingTy :: Type -> Bool
isFloatingTy :: TcType -> Bool
isFloatingTy TcType
ty = TcType -> Bool
isFloatTy TcType
ty Bool -> Bool -> Bool
|| TcType -> Bool
isDoubleTy TcType
ty

-- | Is a type 'String'?
isStringTy :: Type -> Bool
isStringTy :: TcType -> Bool
isStringTy TcType
ty
  = case HasCallStack => TcType -> Maybe (TyCon, [TcType])
TcType -> Maybe (TyCon, [TcType])
tcSplitTyConApp_maybe TcType
ty of
      Just (TyCon
tc, [TcType
arg_ty]) -> TyCon
tc TyCon -> TyCon -> Bool
forall a. Eq a => a -> a -> Bool
== TyCon
listTyCon Bool -> Bool -> Bool
&& TcType -> Bool
isCharTy TcType
arg_ty
      Maybe (TyCon, [TcType])
_                   -> Bool
False

-- | Is a type a 'CallStack'?
isCallStackTy :: Type -> Bool
isCallStackTy :: TcType -> Bool
isCallStackTy TcType
ty
  | Just TyCon
tc <- TcType -> Maybe TyCon
tyConAppTyCon_maybe TcType
ty
  = TyCon
tc TyCon -> Unique -> Bool
forall a. Uniquable a => a -> Unique -> Bool
`hasKey` Unique
callStackTyConKey
  | Bool
otherwise
  = Bool
False

-- | Is a 'PredType' a 'CallStack' implicit parameter?
--
-- If so, return the name of the parameter.
isCallStackPred :: Class -> [Type] -> Maybe FastString
isCallStackPred :: Class -> [TcType] -> Maybe FastString
isCallStackPred Class
cls [TcType]
tys
  | [TcType
ty1, TcType
ty2] <- [TcType]
tys
  , Class -> Bool
isIPClass Class
cls
  , TcType -> Bool
isCallStackTy TcType
ty2
  = TcType -> Maybe FastString
isStrLitTy TcType
ty1
  | Bool
otherwise
  = Maybe FastString
forall a. Maybe a
Nothing

is_tc :: Unique -> Type -> Bool
-- Newtypes are opaque to this
is_tc :: Unique -> TcType -> Bool
is_tc Unique
uniq TcType
ty = case HasCallStack => TcType -> Maybe (TyCon, [TcType])
TcType -> Maybe (TyCon, [TcType])
tcSplitTyConApp_maybe TcType
ty of
                        Just (TyCon
tc, [TcType]
_) -> Unique
uniq Unique -> Unique -> Bool
forall a. Eq a => a -> a -> Bool
== TyCon -> Unique
forall a. Uniquable a => a -> Unique
getUnique TyCon
tc
                        Maybe (TyCon, [TcType])
Nothing      -> Bool
False

-- | Does the given tyvar appear at the head of a chain of applications
--     (a t1 ... tn)
isTyVarHead :: TcTyVar -> TcType -> Bool
isTyVarHead :: TcTyVar -> TcType -> Bool
isTyVarHead TcTyVar
tv (TyVarTy TcTyVar
tv')   = TcTyVar
tv TcTyVar -> TcTyVar -> Bool
forall a. Eq a => a -> a -> Bool
== TcTyVar
tv'
isTyVarHead TcTyVar
tv (AppTy TcType
fun TcType
_)   = TcTyVar -> TcType -> Bool
isTyVarHead TcTyVar
tv TcType
fun
isTyVarHead TcTyVar
tv (CastTy TcType
ty KindCoercion
_)   = TcTyVar -> TcType -> Bool
isTyVarHead TcTyVar
tv TcType
ty
isTyVarHead TcTyVar
_ (TyConApp {})    = Bool
False
isTyVarHead TcTyVar
_  (LitTy {})      = Bool
False
isTyVarHead TcTyVar
_  (ForAllTy {})   = Bool
False
isTyVarHead TcTyVar
_  (FunTy {})      = Bool
False
isTyVarHead TcTyVar
_  (CoercionTy {}) = Bool
False


{- Note [AppTy and ReprEq]
~~~~~~~~~~~~~~~~~~~~~~~~~~
Consider   a ~R# b a
           a ~R# a b

The former is /not/ a definite error; we might instantiate 'b' with Id
   newtype Id a = MkId a
but the latter /is/ a definite error.

On the other hand, with nominal equality, both are definite errors
-}

isRigidTy :: TcType -> Bool
isRigidTy :: TcType -> Bool
isRigidTy TcType
ty
  | Just (TyCon
tc,[TcType]
_) <- HasCallStack => TcType -> Maybe (TyCon, [TcType])
TcType -> Maybe (TyCon, [TcType])
tcSplitTyConApp_maybe TcType
ty = TyCon -> Role -> Bool
isGenerativeTyCon TyCon
tc Role
Nominal
  | Just {} <- TcType -> Maybe (TcType, TcType)
tcSplitAppTy_maybe TcType
ty        = Bool
True
  | TcType -> Bool
isForAllTy TcType
ty                           = Bool
True
  | Bool
otherwise                               = Bool
False


-- | Is this type *almost function-free*? See Note [Almost function-free]
-- in TcRnTypes
isAlmostFunctionFree :: TcType -> Bool
isAlmostFunctionFree :: TcType -> Bool
isAlmostFunctionFree TcType
ty | Just TcType
ty' <- TcType -> Maybe TcType
tcView TcType
ty = TcType -> Bool
isAlmostFunctionFree TcType
ty'
isAlmostFunctionFree (TyVarTy {})    = Bool
True
isAlmostFunctionFree (AppTy TcType
ty1 TcType
ty2) = TcType -> Bool
isAlmostFunctionFree TcType
ty1 Bool -> Bool -> Bool
&&
                                       TcType -> Bool
isAlmostFunctionFree TcType
ty2
isAlmostFunctionFree (TyConApp TyCon
tc [TcType]
args)
  | TyCon -> Bool
isTypeFamilyTyCon TyCon
tc = Bool
False
  | Bool
otherwise            = (TcType -> Bool) -> [TcType] -> Bool
forall (t :: * -> *) a. Foldable t => (a -> Bool) -> t a -> Bool
all TcType -> Bool
isAlmostFunctionFree [TcType]
args
isAlmostFunctionFree (ForAllTy TyCoVarBinder
bndr TcType
_) = TcType -> Bool
isAlmostFunctionFree (TyCoVarBinder -> TcType
forall argf. VarBndr TcTyVar argf -> TcType
binderType TyCoVarBinder
bndr)
isAlmostFunctionFree (FunTy AnonArgFlag
_ TcType
ty1 TcType
ty2) = TcType -> Bool
isAlmostFunctionFree TcType
ty1 Bool -> Bool -> Bool
&&
                                         TcType -> Bool
isAlmostFunctionFree TcType
ty2
isAlmostFunctionFree (LitTy {})        = Bool
True
isAlmostFunctionFree (CastTy TcType
ty KindCoercion
_)     = TcType -> Bool
isAlmostFunctionFree TcType
ty
isAlmostFunctionFree (CoercionTy {})   = Bool
True

{-
************************************************************************
*                                                                      *
\subsection{Misc}
*                                                                      *
************************************************************************

Note [Visible type application]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
GHC implements a generalisation of the algorithm described in the
"Visible Type Application" paper (available from
http://www.cis.upenn.edu/~sweirich/publications.html). A key part
of that algorithm is to distinguish user-specified variables from inferred
variables. For example, the following should typecheck:

  f :: forall a b. a -> b -> b
  f = const id

  g = const id

  x = f @Int @Bool 5 False
  y = g 5 @Bool False

The idea is that we wish to allow visible type application when we are
instantiating a specified, fixed variable. In practice, specified, fixed
variables are either written in a type signature (or
annotation), OR are imported from another module. (We could do better here,
for example by doing SCC analysis on parts of a module and considering any
type from outside one's SCC to be fully specified, but this is very confusing to
users. The simple rule above is much more straightforward and predictable.)

So, both of f's quantified variables are specified and may be instantiated.
But g has no type signature, so only id's variable is specified (because id
is imported). We write the type of g as forall {a}. a -> forall b. b -> b.
Note that the a is in braces, meaning it cannot be instantiated with
visible type application.

Tracking specified vs. inferred variables is done conveniently by a field
in TyBinder.

-}

deNoteType :: Type -> Type
-- Remove all *outermost* type synonyms and other notes
deNoteType :: TcType -> TcType
deNoteType TcType
ty | Just TcType
ty' <- TcType -> Maybe TcType
coreView TcType
ty = TcType -> TcType
deNoteType TcType
ty'
deNoteType TcType
ty = TcType
ty

{-
Find the free tycons and classes of a type.  This is used in the front
end of the compiler.
-}

{-
************************************************************************
*                                                                      *
\subsection[TysWiredIn-ext-type]{External types}
*                                                                      *
************************************************************************

The compiler's foreign function interface supports the passing of a
restricted set of types as arguments and results (the restricting factor
being the )
-}

tcSplitIOType_maybe :: Type -> Maybe (TyCon, Type)
-- (tcSplitIOType_maybe t) returns Just (IO,t',co)
--              if co : t ~ IO t'
--              returns Nothing otherwise
tcSplitIOType_maybe :: TcType -> Maybe (TyCon, TcType)
tcSplitIOType_maybe TcType
ty
  = case HasCallStack => TcType -> Maybe (TyCon, [TcType])
TcType -> Maybe (TyCon, [TcType])
tcSplitTyConApp_maybe TcType
ty of
        Just (TyCon
io_tycon, [TcType
io_res_ty])
         | TyCon
io_tycon TyCon -> Unique -> Bool
forall a. Uniquable a => a -> Unique -> Bool
`hasKey` Unique
ioTyConKey ->
            (TyCon, TcType) -> Maybe (TyCon, TcType)
forall a. a -> Maybe a
Just (TyCon
io_tycon, TcType
io_res_ty)
        Maybe (TyCon, [TcType])
_ ->
            Maybe (TyCon, TcType)
forall a. Maybe a
Nothing

isFFITy :: Type -> Bool
-- True for any TyCon that can possibly be an arg or result of an FFI call
isFFITy :: TcType -> Bool
isFFITy TcType
ty = Validity -> Bool
isValid ((TyCon -> Validity) -> TcType -> Validity
checkRepTyCon TyCon -> Validity
legalFFITyCon TcType
ty)

isFFIArgumentTy :: DynFlags -> Safety -> Type -> Validity
-- Checks for valid argument type for a 'foreign import'
isFFIArgumentTy :: DynFlags -> Safety -> TcType -> Validity
isFFIArgumentTy DynFlags
dflags Safety
safety TcType
ty
   = (TyCon -> Validity) -> TcType -> Validity
checkRepTyCon (DynFlags -> Safety -> TyCon -> Validity
legalOutgoingTyCon DynFlags
dflags Safety
safety) TcType
ty

isFFIExternalTy :: Type -> Validity
-- Types that are allowed as arguments of a 'foreign export'
isFFIExternalTy :: TcType -> Validity
isFFIExternalTy TcType
ty = (TyCon -> Validity) -> TcType -> Validity
checkRepTyCon TyCon -> Validity
legalFEArgTyCon TcType
ty

isFFIImportResultTy :: DynFlags -> Type -> Validity
isFFIImportResultTy :: DynFlags -> TcType -> Validity
isFFIImportResultTy DynFlags
dflags TcType
ty
  = (TyCon -> Validity) -> TcType -> Validity
checkRepTyCon (DynFlags -> TyCon -> Validity
legalFIResultTyCon DynFlags
dflags) TcType
ty

isFFIExportResultTy :: Type -> Validity
isFFIExportResultTy :: TcType -> Validity
isFFIExportResultTy TcType
ty = (TyCon -> Validity) -> TcType -> Validity
checkRepTyCon TyCon -> Validity
legalFEResultTyCon TcType
ty

isFFIDynTy :: Type -> Type -> Validity
-- The type in a foreign import dynamic must be Ptr, FunPtr, or a newtype of
-- either, and the wrapped function type must be equal to the given type.
-- We assume that all types have been run through normaliseFfiType, so we don't
-- need to worry about expanding newtypes here.
isFFIDynTy :: TcType -> TcType -> Validity
isFFIDynTy TcType
expected TcType
ty
    -- Note [Foreign import dynamic]
    -- In the example below, expected would be 'CInt -> IO ()', while ty would
    -- be 'FunPtr (CDouble -> IO ())'.
    | Just (TyCon
tc, [TcType
ty']) <- HasDebugCallStack => TcType -> Maybe (TyCon, [TcType])
TcType -> Maybe (TyCon, [TcType])
splitTyConApp_maybe TcType
ty
    , TyCon -> Unique
tyConUnique TyCon
tc Unique -> [Unique] -> Bool
forall (t :: * -> *) a. (Foldable t, Eq a) => a -> t a -> Bool
`elem` [Unique
ptrTyConKey, Unique
funPtrTyConKey]
    , TcType -> TcType -> Bool
eqType TcType
ty' TcType
expected
    = Validity
IsValid
    | Bool
otherwise
    = SDoc -> Validity
NotValid ([SDoc] -> SDoc
vcat [ String -> SDoc
text String
"Expected: Ptr/FunPtr" SDoc -> SDoc -> SDoc
<+> TcType -> SDoc
pprParendType TcType
expected SDoc -> SDoc -> SDoc
<> SDoc
comma
                     , String -> SDoc
text String
"  Actual:" SDoc -> SDoc -> SDoc
<+> TcType -> SDoc
forall a. Outputable a => a -> SDoc
ppr TcType
ty ])

isFFILabelTy :: Type -> Validity
-- The type of a foreign label must be Ptr, FunPtr, or a newtype of either.
isFFILabelTy :: TcType -> Validity
isFFILabelTy TcType
ty = (TyCon -> Validity) -> TcType -> Validity
checkRepTyCon TyCon -> Validity
forall a. Uniquable a => a -> Validity
ok TcType
ty
  where
    ok :: a -> Validity
ok a
tc | a
tc a -> Unique -> Bool
forall a. Uniquable a => a -> Unique -> Bool
`hasKey` Unique
funPtrTyConKey Bool -> Bool -> Bool
|| a
tc a -> Unique -> Bool
forall a. Uniquable a => a -> Unique -> Bool
`hasKey` Unique
ptrTyConKey
          = Validity
IsValid
          | Bool
otherwise
          = SDoc -> Validity
NotValid (String -> SDoc
text String
"A foreign-imported address (via &foo) must have type (Ptr a) or (FunPtr a)")

isFFIPrimArgumentTy :: DynFlags -> Type -> Validity
-- Checks for valid argument type for a 'foreign import prim'
-- Currently they must all be simple unlifted types, or the well-known type
-- Any, which can be used to pass the address to a Haskell object on the heap to
-- the foreign function.
isFFIPrimArgumentTy :: DynFlags -> TcType -> Validity
isFFIPrimArgumentTy DynFlags
dflags TcType
ty
  | TcType -> Bool
isAnyTy TcType
ty = Validity
IsValid
  | Bool
otherwise  = (TyCon -> Validity) -> TcType -> Validity
checkRepTyCon (DynFlags -> TyCon -> Validity
legalFIPrimArgTyCon DynFlags
dflags) TcType
ty

isFFIPrimResultTy :: DynFlags -> Type -> Validity
-- Checks for valid result type for a 'foreign import prim' Currently
-- it must be an unlifted type, including unboxed tuples, unboxed
-- sums, or the well-known type Any.
isFFIPrimResultTy :: DynFlags -> TcType -> Validity
isFFIPrimResultTy DynFlags
dflags TcType
ty
  | TcType -> Bool
isAnyTy TcType
ty = Validity
IsValid
  | Bool
otherwise = (TyCon -> Validity) -> TcType -> Validity
checkRepTyCon (DynFlags -> TyCon -> Validity
legalFIPrimResultTyCon DynFlags
dflags) TcType
ty

isFunPtrTy :: Type -> Bool
isFunPtrTy :: TcType -> Bool
isFunPtrTy TcType
ty
  | Just (TyCon
tc, [TcType
_]) <- HasDebugCallStack => TcType -> Maybe (TyCon, [TcType])
TcType -> Maybe (TyCon, [TcType])
splitTyConApp_maybe TcType
ty
  = TyCon
tc TyCon -> Unique -> Bool
forall a. Uniquable a => a -> Unique -> Bool
`hasKey` Unique
funPtrTyConKey
  | Bool
otherwise
  = Bool
False

-- normaliseFfiType gets run before checkRepTyCon, so we don't
-- need to worry about looking through newtypes or type functions
-- here; that's already been taken care of.
checkRepTyCon :: (TyCon -> Validity) -> Type -> Validity
checkRepTyCon :: (TyCon -> Validity) -> TcType -> Validity
checkRepTyCon TyCon -> Validity
check_tc TcType
ty
  = case HasDebugCallStack => TcType -> Maybe (TyCon, [TcType])
TcType -> Maybe (TyCon, [TcType])
splitTyConApp_maybe TcType
ty of
      Just (TyCon
tc, [TcType]
tys)
        | TyCon -> Bool
isNewTyCon TyCon
tc -> SDoc -> Validity
NotValid (SDoc -> Int -> SDoc -> SDoc
hang SDoc
msg Int
2 (TyCon -> [TcType] -> SDoc
forall (t :: * -> *) a a.
(Foldable t, Outputable a) =>
a -> t a -> SDoc
mk_nt_reason TyCon
tc [TcType]
tys SDoc -> SDoc -> SDoc
$$ SDoc
nt_fix))
        | Bool
otherwise     -> case TyCon -> Validity
check_tc TyCon
tc of
                             Validity
IsValid        -> Validity
IsValid
                             NotValid SDoc
extra -> SDoc -> Validity
NotValid (SDoc
msg SDoc -> SDoc -> SDoc
$$ SDoc
extra)
      Maybe (TyCon, [TcType])
Nothing -> SDoc -> Validity
NotValid (SDoc -> SDoc
quotes (TcType -> SDoc
forall a. Outputable a => a -> SDoc
ppr TcType
ty) SDoc -> SDoc -> SDoc
<+> String -> SDoc
text String
"is not a data type")
  where
    msg :: SDoc
msg = SDoc -> SDoc
quotes (TcType -> SDoc
forall a. Outputable a => a -> SDoc
ppr TcType
ty) SDoc -> SDoc -> SDoc
<+> String -> SDoc
text String
"cannot be marshalled in a foreign call"
    mk_nt_reason :: a -> t a -> SDoc
mk_nt_reason a
tc t a
tys
      | t a -> Bool
forall (t :: * -> *) a. Foldable t => t a -> Bool
null t a
tys  = String -> SDoc
text String
"because its data constructor is not in scope"
      | Bool
otherwise = String -> SDoc
text String
"because the data constructor for"
                    SDoc -> SDoc -> SDoc
<+> SDoc -> SDoc
quotes (a -> SDoc
forall a. Outputable a => a -> SDoc
ppr a
tc) SDoc -> SDoc -> SDoc
<+> String -> SDoc
text String
"is not in scope"
    nt_fix :: SDoc
nt_fix = String -> SDoc
text String
"Possible fix: import the data constructor to bring it into scope"

{-
Note [Foreign import dynamic]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
A dynamic stub must be of the form 'FunPtr ft -> ft' where ft is any foreign
type.  Similarly, a wrapper stub must be of the form 'ft -> IO (FunPtr ft)'.

We use isFFIDynTy to check whether a signature is well-formed. For example,
given a (illegal) declaration like:

foreign import ccall "dynamic"
  foo :: FunPtr (CDouble -> IO ()) -> CInt -> IO ()

isFFIDynTy will compare the 'FunPtr' type 'CDouble -> IO ()' with the curried
result type 'CInt -> IO ()', and return False, as they are not equal.


----------------------------------------------
These chaps do the work; they are not exported
----------------------------------------------
-}

legalFEArgTyCon :: TyCon -> Validity
legalFEArgTyCon :: TyCon -> Validity
legalFEArgTyCon TyCon
tc
  -- It's illegal to make foreign exports that take unboxed
  -- arguments.  The RTS API currently can't invoke such things.  --SDM 7/2000
  = TyCon -> Validity
boxedMarshalableTyCon TyCon
tc

legalFIResultTyCon :: DynFlags -> TyCon -> Validity
legalFIResultTyCon :: DynFlags -> TyCon -> Validity
legalFIResultTyCon DynFlags
dflags TyCon
tc
  | TyCon
tc TyCon -> TyCon -> Bool
forall a. Eq a => a -> a -> Bool
== TyCon
unitTyCon         = Validity
IsValid
  | Bool
otherwise               = DynFlags -> TyCon -> Validity
marshalableTyCon DynFlags
dflags TyCon
tc

legalFEResultTyCon :: TyCon -> Validity
legalFEResultTyCon :: TyCon -> Validity
legalFEResultTyCon TyCon
tc
  | TyCon
tc TyCon -> TyCon -> Bool
forall a. Eq a => a -> a -> Bool
== TyCon
unitTyCon         = Validity
IsValid
  | Bool
otherwise               = TyCon -> Validity
boxedMarshalableTyCon TyCon
tc

legalOutgoingTyCon :: DynFlags -> Safety -> TyCon -> Validity
-- Checks validity of types going from Haskell -> external world
legalOutgoingTyCon :: DynFlags -> Safety -> TyCon -> Validity
legalOutgoingTyCon DynFlags
dflags Safety
_ TyCon
tc
  = DynFlags -> TyCon -> Validity
marshalableTyCon DynFlags
dflags TyCon
tc

legalFFITyCon :: TyCon -> Validity
-- True for any TyCon that can possibly be an arg or result of an FFI call
legalFFITyCon :: TyCon -> Validity
legalFFITyCon TyCon
tc
  | TyCon -> Bool
isUnliftedTyCon TyCon
tc = Validity
IsValid
  | TyCon
tc TyCon -> TyCon -> Bool
forall a. Eq a => a -> a -> Bool
== TyCon
unitTyCon    = Validity
IsValid
  | Bool
otherwise          = TyCon -> Validity
boxedMarshalableTyCon TyCon
tc

marshalableTyCon :: DynFlags -> TyCon -> Validity
marshalableTyCon :: DynFlags -> TyCon -> Validity
marshalableTyCon DynFlags
dflags TyCon
tc
  | TyCon -> Bool
isUnliftedTyCon TyCon
tc
  , Bool -> Bool
not (TyCon -> Bool
isUnboxedTupleTyCon TyCon
tc Bool -> Bool -> Bool
|| TyCon -> Bool
isUnboxedSumTyCon TyCon
tc)
  , Bool -> Bool
not ([PrimRep] -> Bool
forall (t :: * -> *) a. Foldable t => t a -> Bool
null (HasDebugCallStack => TyCon -> [PrimRep]
TyCon -> [PrimRep]
tyConPrimRep TyCon
tc)) -- Note [Marshalling void]
  = DynFlags -> Validity
validIfUnliftedFFITypes DynFlags
dflags
  | Bool
otherwise
  = TyCon -> Validity
boxedMarshalableTyCon TyCon
tc

boxedMarshalableTyCon :: TyCon -> Validity
boxedMarshalableTyCon :: TyCon -> Validity
boxedMarshalableTyCon TyCon
tc
   | TyCon -> Unique
forall a. Uniquable a => a -> Unique
getUnique TyCon
tc Unique -> [Unique] -> Bool
forall (t :: * -> *) a. (Foldable t, Eq a) => a -> t a -> Bool
`elem` [ Unique
intTyConKey, Unique
int8TyConKey, Unique
int16TyConKey
                         , Unique
int32TyConKey, Unique
int64TyConKey
                         , Unique
wordTyConKey, Unique
word8TyConKey, Unique
word16TyConKey
                         , Unique
word32TyConKey, Unique
word64TyConKey
                         , Unique
floatTyConKey, Unique
doubleTyConKey
                         , Unique
ptrTyConKey, Unique
funPtrTyConKey
                         , Unique
charTyConKey
                         , Unique
stablePtrTyConKey
                         , Unique
boolTyConKey
                         ]
  = Validity
IsValid

  | Bool
otherwise = SDoc -> Validity
NotValid SDoc
empty

legalFIPrimArgTyCon :: DynFlags -> TyCon -> Validity
-- Check args of 'foreign import prim', only allow simple unlifted types.
-- Strictly speaking it is unnecessary to ban unboxed tuples and sums here since
-- currently they're of the wrong kind to use in function args anyway.
legalFIPrimArgTyCon :: DynFlags -> TyCon -> Validity
legalFIPrimArgTyCon DynFlags
dflags TyCon
tc
  | TyCon -> Bool
isUnliftedTyCon TyCon
tc
  , Bool -> Bool
not (TyCon -> Bool
isUnboxedTupleTyCon TyCon
tc Bool -> Bool -> Bool
|| TyCon -> Bool
isUnboxedSumTyCon TyCon
tc)
  = DynFlags -> Validity
validIfUnliftedFFITypes DynFlags
dflags
  | Bool
otherwise
  = SDoc -> Validity
NotValid SDoc
unlifted_only

legalFIPrimResultTyCon :: DynFlags -> TyCon -> Validity
-- Check result type of 'foreign import prim'. Allow simple unlifted
-- types and also unboxed tuple and sum result types.
legalFIPrimResultTyCon :: DynFlags -> TyCon -> Validity
legalFIPrimResultTyCon DynFlags
dflags TyCon
tc
  | TyCon -> Bool
isUnliftedTyCon TyCon
tc
  , TyCon -> Bool
isUnboxedTupleTyCon TyCon
tc Bool -> Bool -> Bool
|| TyCon -> Bool
isUnboxedSumTyCon TyCon
tc
     Bool -> Bool -> Bool
|| Bool -> Bool
not ([PrimRep] -> Bool
forall (t :: * -> *) a. Foldable t => t a -> Bool
null (HasDebugCallStack => TyCon -> [PrimRep]
TyCon -> [PrimRep]
tyConPrimRep TyCon
tc))   -- Note [Marshalling void]
  = DynFlags -> Validity
validIfUnliftedFFITypes DynFlags
dflags

  | Bool
otherwise
  = SDoc -> Validity
NotValid SDoc
unlifted_only

unlifted_only :: MsgDoc
unlifted_only :: SDoc
unlifted_only = String -> SDoc
text String
"foreign import prim only accepts simple unlifted types"

validIfUnliftedFFITypes :: DynFlags -> Validity
validIfUnliftedFFITypes :: DynFlags -> Validity
validIfUnliftedFFITypes DynFlags
dflags
  | Extension -> DynFlags -> Bool
xopt Extension
LangExt.UnliftedFFITypes DynFlags
dflags =  Validity
IsValid
  | Bool
otherwise = SDoc -> Validity
NotValid (String -> SDoc
text String
"To marshal unlifted types, use UnliftedFFITypes")

{-
Note [Marshalling void]
~~~~~~~~~~~~~~~~~~~~~~~
We don't treat State# (whose PrimRep is VoidRep) as marshalable.
In turn that means you can't write
        foreign import foo :: Int -> State# RealWorld

Reason: the back end falls over with panic "primRepHint:VoidRep";
        and there is no compelling reason to permit it
-}

{-
************************************************************************
*                                                                      *
        The "Paterson size" of a type
*                                                                      *
************************************************************************
-}

{-
Note [Paterson conditions on PredTypes]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
We are considering whether *class* constraints terminate
(see Note [Paterson conditions]). Precisely, the Paterson conditions
would have us check that "the constraint has fewer constructors and variables
(taken together and counting repetitions) than the head.".

However, we can be a bit more refined by looking at which kind of constraint
this actually is. There are two main tricks:

 1. It seems like it should be OK not to count the tuple type constructor
    for a PredType like (Show a, Eq a) :: Constraint, since we don't
    count the "implicit" tuple in the ThetaType itself.

    In fact, the Paterson test just checks *each component* of the top level
    ThetaType against the size bound, one at a time. By analogy, it should be
    OK to return the size of the *largest* tuple component as the size of the
    whole tuple.

 2. Once we get into an implicit parameter or equality we
    can't get back to a class constraint, so it's safe
    to say "size 0".  See #4200.

NB: we don't want to detect PredTypes in sizeType (and then call
sizePred on them), or we might get an infinite loop if that PredType
is irreducible. See #5581.
-}

type TypeSize = IntWithInf

sizeType :: Type -> TypeSize
-- Size of a type: the number of variables and constructors
-- Ignore kinds altogether
sizeType :: TcType -> TypeSize
sizeType = TcType -> TypeSize
go
  where
    go :: TcType -> TypeSize
go TcType
ty | Just TcType
exp_ty <- TcType -> Maybe TcType
tcView TcType
ty = TcType -> TypeSize
go TcType
exp_ty
    go (TyVarTy {})              = TypeSize
1
    go (TyConApp TyCon
tc [TcType]
tys)
      | TyCon -> Bool
isTypeFamilyTyCon TyCon
tc     = TypeSize
infinity  -- Type-family applications can
                                             -- expand to any arbitrary size
      | Bool
otherwise                = [TcType] -> TypeSize
sizeTypes (TyCon -> [TcType] -> [TcType]
filterOutInvisibleTypes TyCon
tc [TcType]
tys) TypeSize -> TypeSize -> TypeSize
forall a. Num a => a -> a -> a
+ TypeSize
1
                                   -- Why filter out invisible args?  I suppose any
                                   -- size ordering is sound, but why is this better?
                                   -- I came across this when investigating #14010.
    go (LitTy {})                = TypeSize
1
    go (FunTy AnonArgFlag
_ TcType
arg TcType
res)         = TcType -> TypeSize
go TcType
arg TypeSize -> TypeSize -> TypeSize
forall a. Num a => a -> a -> a
+ TcType -> TypeSize
go TcType
res TypeSize -> TypeSize -> TypeSize
forall a. Num a => a -> a -> a
+ TypeSize
1
    go (AppTy TcType
fun TcType
arg)           = TcType -> TypeSize
go TcType
fun TypeSize -> TypeSize -> TypeSize
forall a. Num a => a -> a -> a
+ TcType -> TypeSize
go TcType
arg
    go (ForAllTy (Bndr TcTyVar
tv ArgFlag
vis) TcType
ty)
        | ArgFlag -> Bool
isVisibleArgFlag ArgFlag
vis   = TcType -> TypeSize
go (TcTyVar -> TcType
tyVarKind TcTyVar
tv) TypeSize -> TypeSize -> TypeSize
forall a. Num a => a -> a -> a
+ TcType -> TypeSize
go TcType
ty TypeSize -> TypeSize -> TypeSize
forall a. Num a => a -> a -> a
+ TypeSize
1
        | Bool
otherwise              = TcType -> TypeSize
go TcType
ty TypeSize -> TypeSize -> TypeSize
forall a. Num a => a -> a -> a
+ TypeSize
1
    go (CastTy TcType
ty KindCoercion
_)             = TcType -> TypeSize
go TcType
ty
    go (CoercionTy {})           = TypeSize
0

sizeTypes :: [Type] -> TypeSize
sizeTypes :: [TcType] -> TypeSize
sizeTypes [TcType]
tys = [TypeSize] -> TypeSize
forall (t :: * -> *) a. (Foldable t, Num a) => t a -> a
sum ((TcType -> TypeSize) -> [TcType] -> [TypeSize]
forall a b. (a -> b) -> [a] -> [b]
map TcType -> TypeSize
sizeType [TcType]
tys)

-----------------------------------------------------------------------------------
-----------------------------------------------------------------------------------
-----------------------
-- | For every arg a tycon can take, the returned list says True if the argument
-- is taken visibly, and False otherwise. Ends with an infinite tail of Trues to
-- allow for oversaturation.
tcTyConVisibilities :: TyCon -> [Bool]
tcTyConVisibilities :: TyCon -> [Bool]
tcTyConVisibilities TyCon
tc = [Bool]
tc_binder_viss [Bool] -> [Bool] -> [Bool]
forall a. [a] -> [a] -> [a]
++ [Bool]
tc_return_kind_viss [Bool] -> [Bool] -> [Bool]
forall a. [a] -> [a] -> [a]
++ Bool -> [Bool]
forall a. a -> [a]
repeat Bool
True
  where
    tc_binder_viss :: [Bool]
tc_binder_viss      = (TyConBinder -> Bool) -> [TyConBinder] -> [Bool]
forall a b. (a -> b) -> [a] -> [b]
map TyConBinder -> Bool
forall tv. VarBndr tv TyConBndrVis -> Bool
isVisibleTyConBinder (TyCon -> [TyConBinder]
tyConBinders TyCon
tc)
    tc_return_kind_viss :: [Bool]
tc_return_kind_viss = (TyBinder -> Bool) -> [TyBinder] -> [Bool]
forall a b. (a -> b) -> [a] -> [b]
map TyBinder -> Bool
isVisibleBinder (([TyBinder], TcType) -> [TyBinder]
forall a b. (a, b) -> a
fst (([TyBinder], TcType) -> [TyBinder])
-> ([TyBinder], TcType) -> [TyBinder]
forall a b. (a -> b) -> a -> b
$ TcType -> ([TyBinder], TcType)
tcSplitPiTys (TyCon -> TcType
tyConResKind TyCon
tc))

-- | If the tycon is applied to the types, is the next argument visible?
isNextTyConArgVisible :: TyCon -> [Type] -> Bool
isNextTyConArgVisible :: TyCon -> [TcType] -> Bool
isNextTyConArgVisible TyCon
tc [TcType]
tys
  = TyCon -> [Bool]
tcTyConVisibilities TyCon
tc [Bool] -> Int -> Bool
forall a. Outputable a => [a] -> Int -> a
`getNth` [TcType] -> Int
forall (t :: * -> *) a. Foldable t => t a -> Int
length [TcType]
tys

-- | Should this type be applied to a visible argument?
isNextArgVisible :: TcType -> Bool
isNextArgVisible :: TcType -> Bool
isNextArgVisible TcType
ty
  | Just (TyBinder
bndr, TcType
_) <- TcType -> Maybe (TyBinder, TcType)
tcSplitPiTy_maybe TcType
ty = TyBinder -> Bool
isVisibleBinder TyBinder
bndr
  | Bool
otherwise                              = Bool
True
    -- this second case might happen if, say, we have an unzonked TauTv.
    -- But TauTvs can't range over types that take invisible arguments