{-
(c) The University of Glasgow 2006-2012
(c) The GRASP Project, Glasgow University, 1992-2002


Various types used during typechecking, please see TcRnMonad as well for
operations on these types. You probably want to import it, instead of this
module.

All the monads exported here are built on top of the same IOEnv monad. The
monad functions like a Reader monad in the way it passes the environment
around. This is done to allow the environment to be manipulated in a stack
like fashion when entering expressions... etc.

For state that is global and should be returned at the end (e.g not part
of the stack mechanism), you should use a TcRef (= IORef) to store them.
-}

{-# LANGUAGE CPP, ExistentialQuantification, GeneralizedNewtypeDeriving,
             ViewPatterns #-}

module TcRnTypes(
        TcRnIf, TcRn, TcM, RnM, IfM, IfL, IfG, -- The monad is opaque outside this module
        TcRef,

        -- The environment types
        Env(..),
        TcGblEnv(..), TcLclEnv(..),
        IfGblEnv(..), IfLclEnv(..),
        tcVisibleOrphanMods,

        -- Frontend types (shouldn't really be here)
        FrontendResult(..),

        -- Renamer types
        ErrCtxt, RecFieldEnv,
        ImportAvails(..), emptyImportAvails, plusImportAvails,
        WhereFrom(..), mkModDeps, modDepsElts,

        -- Typechecker types
        TcTypeEnv, TcBinderStack, TcBinder(..),
        TcTyThing(..), PromotionErr(..),
        IdBindingInfo(..), ClosedTypeId, RhsNames,
        IsGroupClosed(..),
        SelfBootInfo(..),
        pprTcTyThingCategory, pprPECategory, CompleteMatch(..),

        -- Desugaring types
        DsM, DsLclEnv(..), DsGblEnv(..),
        DsMetaEnv, DsMetaVal(..), CompleteMatchMap,
        mkCompleteMatchMap, extendCompleteMatchMap,

        -- Template Haskell
        ThStage(..), SpliceType(..), PendingStuff(..),
        topStage, topAnnStage, topSpliceStage,
        ThLevel, impLevel, outerLevel, thLevel,
        ForeignSrcLang(..),

        -- Arrows
        ArrowCtxt(..),

        -- TcSigInfo
        TcSigFun, TcSigInfo(..), TcIdSigInfo(..),
        TcIdSigInst(..), TcPatSynInfo(..),
        isPartialSig, hasCompleteSig,

        -- QCInst
        QCInst(..), isPendingScInst,

        -- Canonical constraints
        Xi, Ct(..), Cts, emptyCts, andCts, andManyCts, pprCts,
        singleCt, listToCts, ctsElts, consCts, snocCts, extendCtsList,
        isEmptyCts, isCTyEqCan, isCFunEqCan,
        isPendingScDict, superClassesMightHelp, getPendingWantedScs,
        isCDictCan_Maybe, isCFunEqCan_maybe,
        isCNonCanonical, isWantedCt, isDerivedCt,
        isGivenCt, isHoleCt, isOutOfScopeCt, isExprHoleCt, isTypeHoleCt,
        isUserTypeErrorCt, getUserTypeErrorMsg,
        ctEvidence, ctLoc, setCtLoc, ctPred, ctFlavour, ctEqRel, ctOrigin,
        ctEvId, mkTcEqPredLikeEv,
        mkNonCanonical, mkNonCanonicalCt, mkGivens,
        mkIrredCt, mkInsolubleCt,
        ctEvPred, ctEvLoc, ctEvOrigin, ctEvEqRel,
        ctEvExpr, ctEvTerm, ctEvCoercion, ctEvEvId,
        tyCoVarsOfCt, tyCoVarsOfCts,
        tyCoVarsOfCtList, tyCoVarsOfCtsList,

        WantedConstraints(..), insolubleWC, emptyWC, isEmptyWC,
        isSolvedWC, andWC, unionsWC, mkSimpleWC, mkImplicWC,
        addInsols, insolublesOnly, addSimples, addImplics,
        tyCoVarsOfWC, dropDerivedWC, dropDerivedSimples,
        tyCoVarsOfWCList, insolubleCt, insolubleEqCt,
        isDroppableCt, insolubleImplic,
        arisesFromGivens,

        Implication(..), newImplication, implicationPrototype,
        implicLclEnv, implicDynFlags,
        ImplicStatus(..), isInsolubleStatus, isSolvedStatus,
        SubGoalDepth, initialSubGoalDepth, maxSubGoalDepth,
        bumpSubGoalDepth, subGoalDepthExceeded,
        CtLoc(..), ctLocSpan, ctLocEnv, ctLocLevel, ctLocOrigin,
        ctLocTypeOrKind_maybe,
        ctLocDepth, bumpCtLocDepth, isGivenLoc,
        setCtLocOrigin, updateCtLocOrigin, setCtLocEnv, setCtLocSpan,
        CtOrigin(..), exprCtOrigin, lexprCtOrigin, matchesCtOrigin, grhssCtOrigin,
        isVisibleOrigin, toInvisibleOrigin,
        TypeOrKind(..), isTypeLevel, isKindLevel,
        pprCtOrigin, pprCtLoc,
        pushErrCtxt, pushErrCtxtSameOrigin,


        SkolemInfo(..), pprSigSkolInfo, pprSkolInfo,

        CtEvidence(..), TcEvDest(..),
        mkKindLoc, toKindLoc, mkGivenLoc,
        isWanted, isGiven, isDerived, isGivenOrWDeriv,
        ctEvRole,

        wrapType, wrapTypeWithImplication,
        removeBindingShadowing,

        -- Constraint solver plugins
        TcPlugin(..), TcPluginResult(..), TcPluginSolver,
        TcPluginM, runTcPluginM, unsafeTcPluginTcM,
        getEvBindsTcPluginM,

        CtFlavour(..), ShadowInfo(..), ctEvFlavour,
        CtFlavourRole, ctEvFlavourRole, ctFlavourRole,
        eqCanRewrite, eqCanRewriteFR, eqMayRewriteFR,
        eqCanDischargeFR,
        funEqCanDischarge, funEqCanDischargeF,

        -- Pretty printing
        pprEvVarTheta,
        pprEvVars, pprEvVarWithType,

        -- Misc other types
        TcId, TcIdSet,
        Hole(..), holeOcc,
        NameShape(..),

        -- Role annotations
        RoleAnnotEnv, emptyRoleAnnotEnv, mkRoleAnnotEnv,
        lookupRoleAnnot, getRoleAnnots,

  ) where

#include "HsVersions.h"

import GhcPrelude

import HsSyn
import CoreSyn
import HscTypes
import TcEvidence
import Type
import Class    ( Class )
import TyCon    ( TyCon, TyConFlavour, tyConKind )
import TyCoRep  ( coHoleCoVar )
import Coercion ( Coercion, mkHoleCo )
import ConLike  ( ConLike(..) )
import DataCon  ( DataCon, dataConUserType, dataConOrigArgTys )
import PatSyn   ( PatSyn, pprPatSynType )
import Id       ( idType, idName )
import FieldLabel ( FieldLabel )
import TcType
import Annotations
import InstEnv
import FamInstEnv
import PmExpr
import IOEnv
import RdrName
import Name
import NameEnv
import NameSet
import Avail
import Var
import FV
import VarEnv
import Module
import SrcLoc
import VarSet
import ErrUtils
import UniqFM
import UniqSupply
import BasicTypes
import Bag
import DynFlags
import Outputable
import ListSetOps
import FastString
import qualified GHC.LanguageExtensions as LangExt
import Fingerprint
import Util
import PrelNames ( isUnboundName )
import CostCentreState

import Control.Monad (ap, liftM, msum)
import qualified Control.Monad.Fail as MonadFail
import Data.Set      ( Set )
import qualified Data.Set as S

import Data.List ( sort )
import Data.Map ( Map )
import Data.Dynamic  ( Dynamic )
import Data.Typeable ( TypeRep )
import Data.Maybe    ( mapMaybe )
import GHCi.Message
import GHCi.RemoteTypes

import qualified Language.Haskell.TH as TH

-- | A 'NameShape' is a substitution on 'Name's that can be used
-- to refine the identities of a hole while we are renaming interfaces
-- (see 'RnModIface').  Specifically, a 'NameShape' for
-- 'ns_module_name' @A@, defines a mapping from @{A.T}@
-- (for some 'OccName' @T@) to some arbitrary other 'Name'.
--
-- The most intruiging thing about a 'NameShape', however, is
-- how it's constructed.  A 'NameShape' is *implied* by the
-- exported 'AvailInfo's of the implementor of an interface:
-- if an implementor of signature @<H>@ exports @M.T@, you implicitly
-- define a substitution from @{H.T}@ to @M.T@.  So a 'NameShape'
-- is computed from the list of 'AvailInfo's that are exported
-- by the implementation of a module, or successively merged
-- together by the export lists of signatures which are joining
-- together.
--
-- It's not the most obvious way to go about doing this, but it
-- does seem to work!
--
-- NB: Can't boot this and put it in NameShape because then we
-- start pulling in too many DynFlags things.
data NameShape = NameShape {
        NameShape -> ModuleName
ns_mod_name :: ModuleName,
        NameShape -> [AvailInfo]
ns_exports :: [AvailInfo],
        NameShape -> OccEnv Name
ns_map :: OccEnv Name
    }


{-
************************************************************************
*                                                                      *
               Standard monad definition for TcRn
    All the combinators for the monad can be found in TcRnMonad
*                                                                      *
************************************************************************

The monad itself has to be defined here, because it is mentioned by ErrCtxt
-}

type TcRnIf a b = IOEnv (Env a b)
type TcRn       = TcRnIf TcGblEnv TcLclEnv    -- Type inference
type IfM lcl    = TcRnIf IfGblEnv lcl         -- Iface stuff
type IfG        = IfM ()                      --    Top level
type IfL        = IfM IfLclEnv                --    Nested
type DsM        = TcRnIf DsGblEnv DsLclEnv    -- Desugaring

-- TcRn is the type-checking and renaming monad: the main monad that
-- most type-checking takes place in.  The global environment is
-- 'TcGblEnv', which tracks all of the top-level type-checking
-- information we've accumulated while checking a module, while the
-- local environment is 'TcLclEnv', which tracks local information as
-- we move inside expressions.

-- | Historical "renaming monad" (now it's just 'TcRn').
type RnM  = TcRn

-- | Historical "type-checking monad" (now it's just 'TcRn').
type TcM  = TcRn

-- We 'stack' these envs through the Reader like monad infrastructure
-- as we move into an expression (although the change is focused in
-- the lcl type).
data Env gbl lcl
  = Env {
        Env gbl lcl -> HscEnv
env_top  :: !HscEnv, -- Top-level stuff that never changes
                             -- Includes all info about imported things
                             -- BangPattern is to fix leak, see #15111

        Env gbl lcl -> IORef UniqSupply
env_us   :: {-# UNPACK #-} !(IORef UniqSupply),
                             -- Unique supply for local variables

        Env gbl lcl -> gbl
env_gbl  :: gbl,     -- Info about things defined at the top level
                             -- of the module being compiled

        Env gbl lcl -> lcl
env_lcl  :: lcl      -- Nested stuff; changes as we go into
    }

instance ContainsDynFlags (Env gbl lcl) where
    extractDynFlags :: Env gbl lcl -> DynFlags
extractDynFlags env :: Env gbl lcl
env = HscEnv -> DynFlags
hsc_dflags (Env gbl lcl -> HscEnv
forall gbl lcl. Env gbl lcl -> HscEnv
env_top Env gbl lcl
env)

instance ContainsModule gbl => ContainsModule (Env gbl lcl) where
    extractModule :: Env gbl lcl -> Module
extractModule env :: Env gbl lcl
env = gbl -> Module
forall t. ContainsModule t => t -> Module
extractModule (Env gbl lcl -> gbl
forall gbl lcl. Env gbl lcl -> gbl
env_gbl Env gbl lcl
env)


{-
************************************************************************
*                                                                      *
                The interface environments
              Used when dealing with IfaceDecls
*                                                                      *
************************************************************************
-}

data IfGblEnv
  = IfGblEnv {
        -- Some information about where this environment came from;
        -- useful for debugging.
        IfGblEnv -> SDoc
if_doc :: SDoc,
        -- The type environment for the module being compiled,
        -- in case the interface refers back to it via a reference that
        -- was originally a hi-boot file.
        -- We need the module name so we can test when it's appropriate
        -- to look in this env.
        -- See Note [Tying the knot] in TcIface
        IfGblEnv -> Maybe (Module, IfG TypeEnv)
if_rec_types :: Maybe (Module, IfG TypeEnv)
                -- Allows a read effect, so it can be in a mutable
                -- variable; c.f. handling the external package type env
                -- Nothing => interactive stuff, no loops possible
    }

data IfLclEnv
  = IfLclEnv {
        -- The module for the current IfaceDecl
        -- So if we see   f = \x -> x
        -- it means M.f = \x -> x, where M is the if_mod
        -- NB: This is a semantic module, see
        -- Note [Identity versus semantic module]
        IfLclEnv -> Module
if_mod :: Module,

        -- Whether or not the IfaceDecl came from a boot
        -- file or not; we'll use this to choose between
        -- NoUnfolding and BootUnfolding
        IfLclEnv -> Bool
if_boot :: Bool,

        -- The field is used only for error reporting
        -- if (say) there's a Lint error in it
        IfLclEnv -> SDoc
if_loc :: SDoc,
                -- Where the interface came from:
                --      .hi file, or GHCi state, or ext core
                -- plus which bit is currently being examined

        IfLclEnv -> Maybe NameShape
if_nsubst :: Maybe NameShape,

        -- This field is used to make sure "implicit" declarations
        -- (anything that cannot be exported in mi_exports) get
        -- wired up correctly in typecheckIfacesForMerging.  Most
        -- of the time it's @Nothing@.  See Note [Resolving never-exported Names in TcIface]
        -- in TcIface.
        IfLclEnv -> Maybe TypeEnv
if_implicits_env :: Maybe TypeEnv,

        IfLclEnv -> FastStringEnv TyVar
if_tv_env  :: FastStringEnv TyVar,     -- Nested tyvar bindings
        IfLclEnv -> FastStringEnv TyVar
if_id_env  :: FastStringEnv Id         -- Nested id binding
    }

{-
************************************************************************
*                                                                      *
                Desugarer monad
*                                                                      *
************************************************************************

Now the mondo monad magic (yes, @DsM@ is a silly name)---carry around
a @UniqueSupply@ and some annotations, which
presumably include source-file location information:
-}

data DsGblEnv
        = DsGblEnv
        { DsGblEnv -> Module
ds_mod          :: Module             -- For SCC profiling
        , DsGblEnv -> FamInstEnv
ds_fam_inst_env :: FamInstEnv         -- Like tcg_fam_inst_env
        , DsGblEnv -> PrintUnqualified
ds_unqual  :: PrintUnqualified
        , DsGblEnv -> IORef Messages
ds_msgs    :: IORef Messages          -- Warning messages
        , DsGblEnv -> (IfGblEnv, IfLclEnv)
ds_if_env  :: (IfGblEnv, IfLclEnv)    -- Used for looking up global,
                                                -- possibly-imported things
        , DsGblEnv -> CompleteMatchMap
ds_complete_matches :: CompleteMatchMap
           -- Additional complete pattern matches
        , DsGblEnv -> IORef CostCentreState
ds_cc_st   :: IORef CostCentreState
           -- Tracking indices for cost centre annotations
        }

instance ContainsModule DsGblEnv where
    extractModule :: DsGblEnv -> Module
extractModule = DsGblEnv -> Module
ds_mod

data DsLclEnv = DsLclEnv {
        DsLclEnv -> DsMetaEnv
dsl_meta    :: DsMetaEnv,        -- Template Haskell bindings
        DsLclEnv -> RealSrcSpan
dsl_loc     :: RealSrcSpan,      -- To put in pattern-matching error msgs

        -- See Note [Note [Type and Term Equality Propagation] in Check.hs
        -- These two fields are augmented as we walk inwards,
        -- through each patttern match in turn
        DsLclEnv -> Bag TyVar
dsl_dicts   :: Bag EvVar,     -- Constraints from GADT pattern-matching
        DsLclEnv -> Bag SimpleEq
dsl_tm_cs   :: Bag SimpleEq,  -- Constraints form term-level pattern matching

        DsLclEnv -> IORef Int
dsl_pm_iter :: IORef Int  -- Number of iterations for pmcheck so far
                                  -- We fail if this gets too big
     }

-- Inside [| |] brackets, the desugarer looks
-- up variables in the DsMetaEnv
type DsMetaEnv = NameEnv DsMetaVal

data DsMetaVal
   = DsBound Id         -- Bound by a pattern inside the [| |].
                        -- Will be dynamically alpha renamed.
                        -- The Id has type THSyntax.Var

   | DsSplice (HsExpr GhcTc) -- These bindings are introduced by
                             -- the PendingSplices on a HsBracketOut


{-
************************************************************************
*                                                                      *
                Global typechecker environment
*                                                                      *
************************************************************************
-}

-- | 'FrontendResult' describes the result of running the
-- frontend of a Haskell module.  Usually, you'll get
-- a 'FrontendTypecheck', since running the frontend involves
-- typechecking a program, but for an hs-boot merge you'll
-- just get a ModIface, since no actual typechecking occurred.
--
-- This data type really should be in HscTypes, but it needs
-- to have a TcGblEnv which is only defined here.
data FrontendResult
        = FrontendTypecheck TcGblEnv

-- Note [Identity versus semantic module]
-- ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
-- When typechecking an hsig file, it is convenient to keep track
-- of two different "this module" identifiers:
--
--      - The IDENTITY module is simply thisPackage + the module
--        name; i.e. it uniquely *identifies* the interface file
--        we're compiling.  For example, p[A=<A>]:A is an
--        identity module identifying the requirement named A
--        from library p.
--
--      - The SEMANTIC module, which is the actual module that
--        this signature is intended to represent (e.g. if
--        we have a identity module p[A=base:Data.IORef]:A,
--        then the semantic module is base:Data.IORef)
--
-- Which one should you use?
--
--      - In the desugarer and later phases of compilation,
--        identity and semantic modules coincide, since we never compile
--        signatures (we just generate blank object files for
--        hsig files.)
--
--        A corrolary of this is that the following invariant holds at any point
--        past desugaring,
--
--            if I have a Module, this_mod, in hand representing the module
--            currently being compiled,
--            then moduleUnitId this_mod == thisPackage dflags
--
--      - For any code involving Names, we want semantic modules.
--        See lookupIfaceTop in IfaceEnv, mkIface and addFingerprints
--        in MkIface, and tcLookupGlobal in TcEnv
--
--      - When reading interfaces, we want the identity module to
--        identify the specific interface we want (such interfaces
--        should never be loaded into the EPS).  However, if a
--        hole module <A> is requested, we look for A.hi
--        in the home library we are compiling.  (See LoadIface.)
--        Similarly, in RnNames we check for self-imports using
--        identity modules, to allow signatures to import their implementor.
--
--      - For recompilation avoidance, you want the identity module,
--        since that will actually say the specific interface you
--        want to track (and recompile if it changes)

-- | 'TcGblEnv' describes the top-level of the module at the
-- point at which the typechecker is finished work.
-- It is this structure that is handed on to the desugarer
-- For state that needs to be updated during the typechecking
-- phase and returned at end, use a 'TcRef' (= 'IORef').
data TcGblEnv
  = TcGblEnv {
        TcGblEnv -> Module
tcg_mod     :: Module,         -- ^ Module being compiled
        TcGblEnv -> Module
tcg_semantic_mod :: Module,    -- ^ If a signature, the backing module
            -- See also Note [Identity versus semantic module]
        TcGblEnv -> HscSource
tcg_src     :: HscSource,
          -- ^ What kind of module (regular Haskell, hs-boot, hsig)

        TcGblEnv -> GlobalRdrEnv
tcg_rdr_env :: GlobalRdrEnv,   -- ^ Top level envt; used during renaming
        TcGblEnv -> Maybe [Type]
tcg_default :: Maybe [Type],
          -- ^ Types used for defaulting. @Nothing@ => no @default@ decl

        TcGblEnv -> FixityEnv
tcg_fix_env   :: FixityEnv,     -- ^ Just for things in this module
        TcGblEnv -> RecFieldEnv
tcg_field_env :: RecFieldEnv,   -- ^ Just for things in this module
                                        -- See Note [The interactive package] in HscTypes

        TcGblEnv -> TypeEnv
tcg_type_env :: TypeEnv,
          -- ^ Global type env for the module we are compiling now.  All
          -- TyCons and Classes (for this module) end up in here right away,
          -- along with their derived constructors, selectors.
          --
          -- (Ids defined in this module start in the local envt, though they
          --  move to the global envt during zonking)
          --
          -- NB: for what "things in this module" means, see
          -- Note [The interactive package] in HscTypes

        TcGblEnv -> TcRef TypeEnv
tcg_type_env_var :: TcRef TypeEnv,
                -- Used only to initialise the interface-file
                -- typechecker in initIfaceTcRn, so that it can see stuff
                -- bound in this module when dealing with hi-boot recursions
                -- Updated at intervals (e.g. after dealing with types and classes)

        TcGblEnv -> InstEnv
tcg_inst_env     :: !InstEnv,
          -- ^ Instance envt for all /home-package/ modules;
          -- Includes the dfuns in tcg_insts
          -- NB. BangPattern is to fix a leak, see #15111
        TcGblEnv -> FamInstEnv
tcg_fam_inst_env :: !FamInstEnv, -- ^ Ditto for family instances
          -- NB. BangPattern is to fix a leak, see #15111
        TcGblEnv -> AnnEnv
tcg_ann_env      :: AnnEnv,     -- ^ And for annotations

                -- Now a bunch of things about this module that are simply
                -- accumulated, but never consulted until the end.
                -- Nevertheless, it's convenient to accumulate them along
                -- with the rest of the info from this module.
        TcGblEnv -> [AvailInfo]
tcg_exports :: [AvailInfo],     -- ^ What is exported
        TcGblEnv -> ImportAvails
tcg_imports :: ImportAvails,
          -- ^ Information about what was imported from where, including
          -- things bound in this module. Also store Safe Haskell info
          -- here about transitive trusted package requirements.
          --
          -- There are not many uses of this field, so you can grep for
          -- all them.
          --
          -- The ImportAvails records information about the following
          -- things:
          --
          --    1. All of the modules you directly imported (tcRnImports)
          --    2. The orphans (only!) of all imported modules in a GHCi
          --       session (runTcInteractive)
          --    3. The module that instantiated a signature
          --    4. Each of the signatures that merged in
          --
          -- It is used in the following ways:
          --    - imp_orphs is used to determine what orphan modules should be
          --      visible in the context (tcVisibleOrphanMods)
          --    - imp_finsts is used to determine what family instances should
          --      be visible (tcExtendLocalFamInstEnv)
          --    - To resolve the meaning of the export list of a module
          --      (tcRnExports)
          --    - imp_mods is used to compute usage info (mkIfaceTc, deSugar)
          --    - imp_trust_own_pkg is used for Safe Haskell in interfaces
          --      (mkIfaceTc, as well as in HscMain)
          --    - To create the Dependencies field in interface (mkDependencies)

        TcGblEnv -> DefUses
tcg_dus       :: DefUses,   -- ^ What is defined in this module and what is used.
        TcGblEnv -> TcRef [GlobalRdrElt]
tcg_used_gres :: TcRef [GlobalRdrElt],  -- ^ Records occurrences of imported entities
          -- One entry for each occurrence; but may have different GREs for
          -- the same Name See Note [Tracking unused binding and imports]

        TcGblEnv -> TcRef NameSet
tcg_keep :: TcRef NameSet,
          -- ^ Locally-defined top-level names to keep alive.
          --
          -- "Keep alive" means give them an Exported flag, so that the
          -- simplifier does not discard them as dead code, and so that they
          -- are exposed in the interface file (but not to export to the
          -- user).
          --
          -- Some things, like dict-fun Ids and default-method Ids are "born"
          -- with the Exported flag on, for exactly the above reason, but some
          -- we only discover as we go.  Specifically:
          --
          --   * The to/from functions for generic data types
          --
          --   * Top-level variables appearing free in the RHS of an orphan
          --     rule
          --
          --   * Top-level variables appearing free in a TH bracket

        TcGblEnv -> TcRef Bool
tcg_th_used :: TcRef Bool,
          -- ^ @True@ <=> Template Haskell syntax used.
          --
          -- We need this so that we can generate a dependency on the
          -- Template Haskell package, because the desugarer is going
          -- to emit loads of references to TH symbols.  The reference
          -- is implicit rather than explicit, so we have to zap a
          -- mutable variable.

        TcGblEnv -> TcRef Bool
tcg_th_splice_used :: TcRef Bool,
          -- ^ @True@ <=> A Template Haskell splice was used.
          --
          -- Splices disable recompilation avoidance (see #481)

        TcGblEnv -> TcRef (Set RealSrcSpan)
tcg_th_top_level_locs :: TcRef (Set RealSrcSpan),
          -- ^ Locations of the top-level splices; used for providing details on
          -- scope in error messages for out-of-scope variables

        TcGblEnv -> TcRef OccSet
tcg_dfun_n  :: TcRef OccSet,
          -- ^ Allows us to choose unique DFun names.

        TcGblEnv -> [(Module, Fingerprint)]
tcg_merged :: [(Module, Fingerprint)],
          -- ^ The requirements we merged with; we always have to recompile
          -- if any of these changed.

        -- The next fields accumulate the payload of the module
        -- The binds, rules and foreign-decl fields are collected
        -- initially in un-zonked form and are finally zonked in tcRnSrcDecls

        TcGblEnv -> Maybe [(Located (IE GhcRn), [AvailInfo])]
tcg_rn_exports :: Maybe [(Located (IE GhcRn), Avails)],
                -- Nothing <=> no explicit export list
                -- Is always Nothing if we don't want to retain renamed
                -- exports.
                -- If present contains each renamed export list item
                -- together with its exported names.

        TcGblEnv -> [LImportDecl GhcRn]
tcg_rn_imports :: [LImportDecl GhcRn],
                -- Keep the renamed imports regardless.  They are not
                -- voluminous and are needed if you want to report unused imports

        TcGblEnv -> Maybe (HsGroup GhcRn)
tcg_rn_decls :: Maybe (HsGroup GhcRn),
          -- ^ Renamed decls, maybe.  @Nothing@ <=> Don't retain renamed
          -- decls.

        TcGblEnv -> TcRef [FilePath]
tcg_dependent_files :: TcRef [FilePath], -- ^ dependencies from addDependentFile

        TcGblEnv -> TcRef [LHsDecl GhcPs]
tcg_th_topdecls :: TcRef [LHsDecl GhcPs],
        -- ^ Top-level declarations from addTopDecls

        TcGblEnv -> TcRef [(ForeignSrcLang, FilePath)]
tcg_th_foreign_files :: TcRef [(ForeignSrcLang, FilePath)],
        -- ^ Foreign files emitted from TH.

        TcGblEnv -> TcRef NameSet
tcg_th_topnames :: TcRef NameSet,
        -- ^ Exact names bound in top-level declarations in tcg_th_topdecls

        TcGblEnv -> TcRef [(TcLclEnv, ThModFinalizers)]
tcg_th_modfinalizers :: TcRef [(TcLclEnv, ThModFinalizers)],
        -- ^ Template Haskell module finalizers.
        --
        -- They can use particular local environments.

        TcGblEnv -> TcRef [FilePath]
tcg_th_coreplugins :: TcRef [String],
        -- ^ Core plugins added by Template Haskell code.

        TcGblEnv -> TcRef (Map TypeRep Dynamic)
tcg_th_state :: TcRef (Map TypeRep Dynamic),
        TcGblEnv -> TcRef (Maybe (ForeignRef (IORef QState)))
tcg_th_remote_state :: TcRef (Maybe (ForeignRef (IORef QState))),
        -- ^ Template Haskell state

        TcGblEnv -> Bag EvBind
tcg_ev_binds  :: Bag EvBind,        -- Top-level evidence bindings

        -- Things defined in this module, or (in GHCi)
        -- in the declarations for a single GHCi command.
        -- For the latter, see Note [The interactive package] in HscTypes
        TcGblEnv -> Maybe TyVar
tcg_tr_module :: Maybe Id,   -- Id for $trModule :: GHC.Types.Module
                                             -- for which every module has a top-level defn
                                             -- except in GHCi in which case we have Nothing
        TcGblEnv -> LHsBinds GhcTc
tcg_binds     :: LHsBinds GhcTc,     -- Value bindings in this module
        TcGblEnv -> NameSet
tcg_sigs      :: NameSet,            -- ...Top-level names that *lack* a signature
        TcGblEnv -> [LTcSpecPrag]
tcg_imp_specs :: [LTcSpecPrag],      -- ...SPECIALISE prags for imported Ids
        TcGblEnv -> Warnings
tcg_warns     :: Warnings,           -- ...Warnings and deprecations
        TcGblEnv -> [Annotation]
tcg_anns      :: [Annotation],       -- ...Annotations
        TcGblEnv -> [TyCon]
tcg_tcs       :: [TyCon],            -- ...TyCons and Classes
        TcGblEnv -> [ClsInst]
tcg_insts     :: [ClsInst],          -- ...Instances
        TcGblEnv -> [FamInst]
tcg_fam_insts :: [FamInst],          -- ...Family instances
        TcGblEnv -> [LRuleDecl GhcTc]
tcg_rules     :: [LRuleDecl GhcTc],  -- ...Rules
        TcGblEnv -> [LForeignDecl GhcTc]
tcg_fords     :: [LForeignDecl GhcTc], -- ...Foreign import & exports
        TcGblEnv -> [PatSyn]
tcg_patsyns   :: [PatSyn],            -- ...Pattern synonyms

        TcGblEnv -> Maybe LHsDocString
tcg_doc_hdr   :: Maybe LHsDocString, -- ^ Maybe Haddock header docs
        TcGblEnv -> Bool
tcg_hpc       :: !AnyHpcUsage,       -- ^ @True@ if any part of the
                                             --  prog uses hpc instrumentation.
           -- NB. BangPattern is to fix a leak, see #15111

        TcGblEnv -> SelfBootInfo
tcg_self_boot :: SelfBootInfo,       -- ^ Whether this module has a
                                             -- corresponding hi-boot file

        TcGblEnv -> Maybe Name
tcg_main      :: Maybe Name,         -- ^ The Name of the main
                                             -- function, if this module is
                                             -- the main module.

        TcGblEnv -> TcRef (Bool, WarningMessages)
tcg_safeInfer :: TcRef (Bool, WarningMessages),
        -- ^ Has the typechecker inferred this module as -XSafe (Safe Haskell)
        -- See Note [Safe Haskell Overlapping Instances Implementation],
        -- although this is used for more than just that failure case.

        TcGblEnv -> [TcPluginSolver]
tcg_tc_plugins :: [TcPluginSolver],
        -- ^ A list of user-defined plugins for the constraint solver.

        TcGblEnv -> RealSrcSpan
tcg_top_loc :: RealSrcSpan,
        -- ^ The RealSrcSpan this module came from

        TcGblEnv -> TcRef WantedConstraints
tcg_static_wc :: TcRef WantedConstraints,
          -- ^ Wanted constraints of static forms.
        -- See Note [Constraints in static forms].
        TcGblEnv -> [CompleteMatch]
tcg_complete_matches :: [CompleteMatch],

        -- ^ Tracking indices for cost centre annotations
        TcGblEnv -> IORef CostCentreState
tcg_cc_st   :: TcRef CostCentreState
    }

-- NB: topModIdentity, not topModSemantic!
-- Definition sites of orphan identities will be identity modules, not semantic
-- modules.

-- Note [Constraints in static forms]
-- ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
--
-- When a static form produces constraints like
--
-- f :: StaticPtr (Bool -> String)
-- f = static show
--
-- we collect them in tcg_static_wc and resolve them at the end
-- of type checking. They need to be resolved separately because
-- we don't want to resolve them in the context of the enclosing
-- expression. Consider
--
-- g :: Show a => StaticPtr (a -> String)
-- g = static show
--
-- If the @Show a0@ constraint that the body of the static form produces was
-- resolved in the context of the enclosing expression, then the body of the
-- static form wouldn't be closed because the Show dictionary would come from
-- g's context instead of coming from the top level.

tcVisibleOrphanMods :: TcGblEnv -> ModuleSet
tcVisibleOrphanMods :: TcGblEnv -> ModuleSet
tcVisibleOrphanMods tcg_env :: TcGblEnv
tcg_env
    = [Module] -> ModuleSet
mkModuleSet (TcGblEnv -> Module
tcg_mod TcGblEnv
tcg_env Module -> [Module] -> [Module]
forall a. a -> [a] -> [a]
: ImportAvails -> [Module]
imp_orphs (TcGblEnv -> ImportAvails
tcg_imports TcGblEnv
tcg_env))

instance ContainsModule TcGblEnv where
    extractModule :: TcGblEnv -> Module
extractModule env :: TcGblEnv
env = TcGblEnv -> Module
tcg_semantic_mod TcGblEnv
env

type RecFieldEnv = NameEnv [FieldLabel]
        -- Maps a constructor name *in this module*
        -- to the fields for that constructor.
        -- This is used when dealing with ".." notation in record
        -- construction and pattern matching.
        -- The FieldEnv deals *only* with constructors defined in *this*
        -- module.  For imported modules, we get the same info from the
        -- TypeEnv

data SelfBootInfo
  = NoSelfBoot    -- No corresponding hi-boot file
  | SelfBoot
       { SelfBootInfo -> ModDetails
sb_mds :: ModDetails   -- There was a hi-boot file,
       , SelfBootInfo -> NameSet
sb_tcs :: NameSet }    -- defining these TyCons,
-- What is sb_tcs used for?  See Note [Extra dependencies from .hs-boot files]
-- in RnSource


{- Note [Tracking unused binding and imports]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
We gather two sorts of usage information

 * tcg_dus (defs/uses)
      Records *defined* Names (local, top-level)
          and *used*    Names (local or imported)

      Used (a) to report "defined but not used"
               (see RnNames.reportUnusedNames)
           (b) to generate version-tracking usage info in interface
               files (see MkIface.mkUsedNames)
   This usage info is mainly gathered by the renamer's
   gathering of free-variables

 * tcg_used_gres
      Used only to report unused import declarations

      Records each *occurrence* an *imported* (not locally-defined) entity.
      The occurrence is recorded by keeping a GlobalRdrElt for it.
      These is not the GRE that is in the GlobalRdrEnv; rather it
      is recorded *after* the filtering done by pickGREs.  So it reflect
      /how that occurrence is in scope/.   See Note [GRE filtering] in
      RdrName.


************************************************************************
*                                                                      *
                The local typechecker environment
*                                                                      *
************************************************************************

Note [The Global-Env/Local-Env story]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
During type checking, we keep in the tcg_type_env
        * All types and classes
        * All Ids derived from types and classes (constructors, selectors)

At the end of type checking, we zonk the local bindings,
and as we do so we add to the tcg_type_env
        * Locally defined top-level Ids

Why?  Because they are now Ids not TcIds.  This final GlobalEnv is
        a) fed back (via the knot) to typechecking the
           unfoldings of interface signatures
        b) used in the ModDetails of this module
-}

data TcLclEnv           -- Changes as we move inside an expression
                        -- Discarded after typecheck/rename; not passed on to desugarer
  = TcLclEnv {
        TcLclEnv -> RealSrcSpan
tcl_loc        :: RealSrcSpan,     -- Source span
        TcLclEnv -> [ErrCtxt]
tcl_ctxt       :: [ErrCtxt],       -- Error context, innermost on top
        TcLclEnv -> TcLevel
tcl_tclvl      :: TcLevel,         -- Birthplace for new unification variables

        TcLclEnv -> ThStage
tcl_th_ctxt    :: ThStage,         -- Template Haskell context
        TcLclEnv -> ThBindEnv
tcl_th_bndrs   :: ThBindEnv,       -- and binder info
            -- The ThBindEnv records the TH binding level of in-scope Names
            -- defined in this module (not imported)
            -- We can't put this info in the TypeEnv because it's needed
            -- (and extended) in the renamer, for untyed splices

        TcLclEnv -> ArrowCtxt
tcl_arrow_ctxt :: ArrowCtxt,       -- Arrow-notation context

        TcLclEnv -> LocalRdrEnv
tcl_rdr :: LocalRdrEnv,         -- Local name envt
                -- Maintained during renaming, of course, but also during
                -- type checking, solely so that when renaming a Template-Haskell
                -- splice we have the right environment for the renamer.
                --
                --   Does *not* include global name envt; may shadow it
                --   Includes both ordinary variables and type variables;
                --   they are kept distinct because tyvar have a different
                --   occurrence constructor (Name.TvOcc)
                -- We still need the unsullied global name env so that
                --   we can look up record field names

        TcLclEnv -> TcTypeEnv
tcl_env  :: TcTypeEnv,    -- The local type environment:
                                  -- Ids and TyVars defined in this module

        TcLclEnv -> TcBinderStack
tcl_bndrs :: TcBinderStack,   -- Used for reporting relevant bindings,
                                      -- and for tidying types

        TcLclEnv -> TcRef TcTyVarSet
tcl_tyvars :: TcRef TcTyVarSet, -- The "global tyvars"
                        -- Namely, the in-scope TyVars bound in tcl_env,
                        -- plus the tyvars mentioned in the types of Ids bound
                        -- in tcl_lenv.
                        -- Why mutable? see notes with tcGetGlobalTyCoVars

        TcLclEnv -> TcRef WantedConstraints
tcl_lie  :: TcRef WantedConstraints,    -- Place to accumulate type constraints
        TcLclEnv -> IORef Messages
tcl_errs :: TcRef Messages              -- Place to accumulate errors
    }

type ErrCtxt = (Bool, TidyEnv -> TcM (TidyEnv, MsgDoc))
        -- Monadic so that we have a chance
        -- to deal with bound type variables just before error
        -- message construction

        -- Bool:  True <=> this is a landmark context; do not
        --                 discard it when trimming for display

type TcTypeEnv = NameEnv TcTyThing

type ThBindEnv = NameEnv (TopLevelFlag, ThLevel)
   -- Domain = all Ids bound in this module (ie not imported)
   -- The TopLevelFlag tells if the binding is syntactically top level.
   -- We need to know this, because the cross-stage persistence story allows
   -- cross-stage at arbitrary types if the Id is bound at top level.
   --
   -- Nota bene: a ThLevel of 'outerLevel' is *not* the same as being
   -- bound at top level!  See Note [Template Haskell levels] in TcSplice

{- Note [Given Insts]
   ~~~~~~~~~~~~~~~~~~
Because of GADTs, we have to pass inwards the Insts provided by type signatures
and existential contexts. Consider
        data T a where { T1 :: b -> b -> T [b] }
        f :: Eq a => T a -> Bool
        f (T1 x y) = [x]==[y]

The constructor T1 binds an existential variable 'b', and we need Eq [b].
Well, we have it, because Eq a refines to Eq [b], but we can only spot that if we
pass it inwards.

-}

-- | Type alias for 'IORef'; the convention is we'll use this for mutable
-- bits of data in 'TcGblEnv' which are updated during typechecking and
-- returned at the end.
type TcRef a     = IORef a
-- ToDo: when should I refer to it as a 'TcId' instead of an 'Id'?
type TcId        = Id
type TcIdSet     = IdSet

---------------------------
-- The TcBinderStack
---------------------------

type TcBinderStack = [TcBinder]
   -- This is a stack of locally-bound ids and tyvars,
   --   innermost on top
   -- Used only in error reporting (relevantBindings in TcError),
   --   and in tidying
   -- We can't use the tcl_env type environment, because it doesn't
   --   keep track of the nesting order

data TcBinder
  = TcIdBndr
       TcId
       TopLevelFlag    -- Tells whether the binding is syntactically top-level
                       -- (The monomorphic Ids for a recursive group count
                       --  as not-top-level for this purpose.)

  | TcIdBndr_ExpType  -- Variant that allows the type to be specified as
                      -- an ExpType
       Name
       ExpType
       TopLevelFlag

  | TcTvBndr          -- e.g.   case x of P (y::a) -> blah
       Name           -- We bind the lexical name "a" to the type of y,
       TyVar          -- which might be an utterly different (perhaps
                      -- existential) tyvar

instance Outputable TcBinder where
   ppr :: TcBinder -> SDoc
ppr (TcIdBndr id :: TyVar
id top_lvl :: TopLevelFlag
top_lvl)           = TyVar -> SDoc
forall a. Outputable a => a -> SDoc
ppr TyVar
id SDoc -> SDoc -> SDoc
<> SDoc -> SDoc
brackets (TopLevelFlag -> SDoc
forall a. Outputable a => a -> SDoc
ppr TopLevelFlag
top_lvl)
   ppr (TcIdBndr_ExpType id :: Name
id _ top_lvl :: TopLevelFlag
top_lvl) = Name -> SDoc
forall a. Outputable a => a -> SDoc
ppr Name
id SDoc -> SDoc -> SDoc
<> SDoc -> SDoc
brackets (TopLevelFlag -> SDoc
forall a. Outputable a => a -> SDoc
ppr TopLevelFlag
top_lvl)
   ppr (TcTvBndr name :: Name
name tv :: TyVar
tv)              = Name -> SDoc
forall a. Outputable a => a -> SDoc
ppr Name
name SDoc -> SDoc -> SDoc
<+> TyVar -> SDoc
forall a. Outputable a => a -> SDoc
ppr TyVar
tv

instance HasOccName TcBinder where
    occName :: TcBinder -> OccName
occName (TcIdBndr id :: TyVar
id _)             = Name -> OccName
forall name. HasOccName name => name -> OccName
occName (TyVar -> Name
idName TyVar
id)
    occName (TcIdBndr_ExpType name :: Name
name _ _) = Name -> OccName
forall name. HasOccName name => name -> OccName
occName Name
name
    occName (TcTvBndr name :: Name
name _)           = Name -> OccName
forall name. HasOccName name => name -> OccName
occName Name
name

-- fixes #12177
-- Builds up a list of bindings whose OccName has not been seen before
-- i.e., If    ys  = removeBindingShadowing xs
-- then
--  - ys is obtained from xs by deleting some elements
--  - ys has no duplicate OccNames
--  - The first duplicated OccName in xs is retained in ys
-- Overloaded so that it can be used for both GlobalRdrElt in typed-hole
-- substitutions and TcBinder when looking for relevant bindings.
removeBindingShadowing :: HasOccName a => [a] -> [a]
removeBindingShadowing :: [a] -> [a]
removeBindingShadowing bindings :: [a]
bindings = [a] -> [a]
forall a. [a] -> [a]
reverse ([a] -> [a]) -> [a] -> [a]
forall a b. (a -> b) -> a -> b
$ ([a], OccSet) -> [a]
forall a b. (a, b) -> a
fst (([a], OccSet) -> [a]) -> ([a], OccSet) -> [a]
forall a b. (a -> b) -> a -> b
$ (([a], OccSet) -> a -> ([a], OccSet))
-> ([a], OccSet) -> [a] -> ([a], OccSet)
forall (t :: * -> *) b a.
Foldable t =>
(b -> a -> b) -> b -> t a -> b
foldl
    (\(bindingAcc :: [a]
bindingAcc, seenNames :: OccSet
seenNames) binding :: a
binding ->
    if a -> OccName
forall name. HasOccName name => name -> OccName
occName a
binding OccName -> OccSet -> Bool
`elemOccSet` OccSet
seenNames -- if we've seen it
        then ([a]
bindingAcc, OccSet
seenNames)              -- skip it
        else (a
bindinga -> [a] -> [a]
forall a. a -> [a] -> [a]
:[a]
bindingAcc, OccSet -> OccName -> OccSet
extendOccSet OccSet
seenNames (a -> OccName
forall name. HasOccName name => name -> OccName
occName a
binding)))
    ([], OccSet
emptyOccSet) [a]
bindings

---------------------------
-- Template Haskell stages and levels
---------------------------

data SpliceType = Typed | Untyped

data ThStage    -- See Note [Template Haskell state diagram] in TcSplice
  = Splice SpliceType -- Inside a top-level splice
                      -- This code will be run *at compile time*;
                      --   the result replaces the splice
                      -- Binding level = 0

  | RunSplice (TcRef [ForeignRef (TH.Q ())])
      -- Set when running a splice, i.e. NOT when renaming or typechecking the
      -- Haskell code for the splice. See Note [RunSplice ThLevel].
      --
      -- Contains a list of mod finalizers collected while executing the splice.
      --
      -- 'addModFinalizer' inserts finalizers here, and from here they are taken
      -- to construct an @HsSpliced@ annotation for untyped splices. See Note
      -- [Delaying modFinalizers in untyped splices] in "RnSplice".
      --
      -- For typed splices, the typechecker takes finalizers from here and
      -- inserts them in the list of finalizers in the global environment.
      --
      -- See Note [Collecting modFinalizers in typed splices] in "TcSplice".

  | Comp        -- Ordinary Haskell code
                -- Binding level = 1

  | Brack                       -- Inside brackets
      ThStage                   --   Enclosing stage
      PendingStuff

data PendingStuff
  = RnPendingUntyped              -- Renaming the inside of an *untyped* bracket
      (TcRef [PendingRnSplice])   -- Pending splices in here

  | RnPendingTyped                -- Renaming the inside of a *typed* bracket

  | TcPending                     -- Typechecking the inside of a typed bracket
      (TcRef [PendingTcSplice])   --   Accumulate pending splices here
      (TcRef WantedConstraints)   --     and type constraints here

topStage, topAnnStage, topSpliceStage :: ThStage
topStage :: ThStage
topStage       = ThStage
Comp
topAnnStage :: ThStage
topAnnStage    = SpliceType -> ThStage
Splice SpliceType
Untyped
topSpliceStage :: ThStage
topSpliceStage = SpliceType -> ThStage
Splice SpliceType
Untyped

instance Outputable ThStage where
   ppr :: ThStage -> SDoc
ppr (Splice _)    = FilePath -> SDoc
text "Splice"
   ppr (RunSplice _) = FilePath -> SDoc
text "RunSplice"
   ppr Comp          = FilePath -> SDoc
text "Comp"
   ppr (Brack s :: ThStage
s _)   = FilePath -> SDoc
text "Brack" SDoc -> SDoc -> SDoc
<> SDoc -> SDoc
parens (ThStage -> SDoc
forall a. Outputable a => a -> SDoc
ppr ThStage
s)

type ThLevel = Int
    -- NB: see Note [Template Haskell levels] in TcSplice
    -- Incremented when going inside a bracket,
    -- decremented when going inside a splice
    -- NB: ThLevel is one greater than the 'n' in Fig 2 of the
    --     original "Template meta-programming for Haskell" paper

impLevel, outerLevel :: ThLevel
impLevel :: Int
impLevel = 0    -- Imported things; they can be used inside a top level splice
outerLevel :: Int
outerLevel = 1  -- Things defined outside brackets

thLevel :: ThStage -> ThLevel
thLevel :: ThStage -> Int
thLevel (Splice _)    = 0
thLevel (RunSplice _) =
    -- See Note [RunSplice ThLevel].
    FilePath -> Int
forall a. FilePath -> a
panic "thLevel: called when running a splice"
thLevel Comp          = 1
thLevel (Brack s :: ThStage
s _)   = ThStage -> Int
thLevel ThStage
s Int -> Int -> Int
forall a. Num a => a -> a -> a
+ 1

{- Node [RunSplice ThLevel]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~
The 'RunSplice' stage is set when executing a splice, and only when running a
splice. In particular it is not set when the splice is renamed or typechecked.

'RunSplice' is needed to provide a reference where 'addModFinalizer' can insert
the finalizer (see Note [Delaying modFinalizers in untyped splices]), and
'addModFinalizer' runs when doing Q things. Therefore, It doesn't make sense to
set 'RunSplice' when renaming or typechecking the splice, where 'Splice', 
'Brack' or 'Comp' are used instead.

-}

---------------------------
-- Arrow-notation context
---------------------------

{- Note [Escaping the arrow scope]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
In arrow notation, a variable bound by a proc (or enclosed let/kappa)
is not in scope to the left of an arrow tail (-<) or the head of (|..|).
For example

        proc x -> (e1 -< e2)

Here, x is not in scope in e1, but it is in scope in e2.  This can get
a bit complicated:

        let x = 3 in
        proc y -> (proc z -> e1) -< e2

Here, x and z are in scope in e1, but y is not.

We implement this by
recording the environment when passing a proc (using newArrowScope),
and returning to that (using escapeArrowScope) on the left of -< and the
head of (|..|).

All this can be dealt with by the *renamer*. But the type checker needs
to be involved too.  Example (arrowfail001)
  class Foo a where foo :: a -> ()
  data Bar = forall a. Foo a => Bar a
  get :: Bar -> ()
  get = proc x -> case x of Bar a -> foo -< a
Here the call of 'foo' gives rise to a (Foo a) constraint that should not
be captured by the pattern match on 'Bar'.  Rather it should join the
constraints from further out.  So we must capture the constraint bag
from further out in the ArrowCtxt that we push inwards.
-}

data ArrowCtxt   -- Note [Escaping the arrow scope]
  = NoArrowCtxt
  | ArrowCtxt LocalRdrEnv (TcRef WantedConstraints)


---------------------------
-- TcTyThing
---------------------------

-- | A typecheckable thing available in a local context.  Could be
-- 'AGlobal' 'TyThing', but also lexically scoped variables, etc.
-- See 'TcEnv' for how to retrieve a 'TyThing' given a 'Name'.
data TcTyThing
  = AGlobal TyThing             -- Used only in the return type of a lookup

  | ATcId           -- Ids defined in this module; may not be fully zonked
      { TcTyThing -> TyVar
tct_id   :: TcId
      , TcTyThing -> IdBindingInfo
tct_info :: IdBindingInfo   -- See Note [Meaning of IdBindingInfo]
      }

  | ATyVar  Name TcTyVar   -- See Note [Type variables in the type environment]

  | ATcTyCon TyCon   -- Used temporarily, during kind checking, for the
                     -- tycons and clases in this recursive group
                     -- The TyCon is always a TcTyCon.  Its kind
                     -- can be a mono-kind or a poly-kind; in TcTyClsDcls see
                     -- Note [Type checking recursive type and class declarations]

  | APromotionErr PromotionErr

data PromotionErr
  = TyConPE          -- TyCon used in a kind before we are ready
                     --     data T :: T -> * where ...
  | ClassPE          -- Ditto Class

  | FamDataConPE     -- Data constructor for a data family
                     -- See Note [AFamDataCon: not promoting data family constructors]
                     -- in TcEnv.
  | ConstrainedDataConPE PredType
                     -- Data constructor with a non-equality context
                     -- See Note [Don't promote data constructors with
                     --           non-equality contexts] in TcHsType
  | PatSynPE         -- Pattern synonyms
                     -- See Note [Don't promote pattern synonyms] in TcEnv

  | PatSynExPE       -- Pattern synonym existential type variable
                     -- See Note [Pattern synonym existentials do not scope] in TcPatSyn

  | RecDataConPE     -- Data constructor in a recursive loop
                     -- See Note [Recursion and promoting data constructors] in TcTyClsDecls
  | NoDataKindsTC    -- -XDataKinds not enabled (for a tycon)
  | NoDataKindsDC    -- -XDataKinds not enabled (for a datacon)

instance Outputable TcTyThing where     -- Debugging only
   ppr :: TcTyThing -> SDoc
ppr (AGlobal g :: TyThing
g)      = TyThing -> SDoc
forall a. Outputable a => a -> SDoc
ppr TyThing
g
   ppr elt :: TcTyThing
elt@(ATcId {})   = FilePath -> SDoc
text "Identifier" SDoc -> SDoc -> SDoc
<>
                          SDoc -> SDoc
brackets (TyVar -> SDoc
forall a. Outputable a => a -> SDoc
ppr (TcTyThing -> TyVar
tct_id TcTyThing
elt) SDoc -> SDoc -> SDoc
<> SDoc
dcolon
                                 SDoc -> SDoc -> SDoc
<> Type -> SDoc
forall a. Outputable a => a -> SDoc
ppr (TyVar -> Type
varType (TcTyThing -> TyVar
tct_id TcTyThing
elt)) SDoc -> SDoc -> SDoc
<> SDoc
comma
                                 SDoc -> SDoc -> SDoc
<+> IdBindingInfo -> SDoc
forall a. Outputable a => a -> SDoc
ppr (TcTyThing -> IdBindingInfo
tct_info TcTyThing
elt))
   ppr (ATyVar n :: Name
n tv :: TyVar
tv)    = FilePath -> SDoc
text "Type variable" SDoc -> SDoc -> SDoc
<+> SDoc -> SDoc
quotes (Name -> SDoc
forall a. Outputable a => a -> SDoc
ppr Name
n) SDoc -> SDoc -> SDoc
<+> SDoc
equals SDoc -> SDoc -> SDoc
<+> TyVar -> SDoc
forall a. Outputable a => a -> SDoc
ppr TyVar
tv
                            SDoc -> SDoc -> SDoc
<+> SDoc
dcolon SDoc -> SDoc -> SDoc
<+> Type -> SDoc
forall a. Outputable a => a -> SDoc
ppr (TyVar -> Type
varType TyVar
tv)
   ppr (ATcTyCon tc :: TyCon
tc)    = FilePath -> SDoc
text "ATcTyCon" SDoc -> SDoc -> SDoc
<+> TyCon -> SDoc
forall a. Outputable a => a -> SDoc
ppr TyCon
tc SDoc -> SDoc -> SDoc
<+> SDoc
dcolon SDoc -> SDoc -> SDoc
<+> Type -> SDoc
forall a. Outputable a => a -> SDoc
ppr (TyCon -> Type
tyConKind TyCon
tc)
   ppr (APromotionErr err :: PromotionErr
err) = FilePath -> SDoc
text "APromotionErr" SDoc -> SDoc -> SDoc
<+> PromotionErr -> SDoc
forall a. Outputable a => a -> SDoc
ppr PromotionErr
err

-- | IdBindingInfo describes how an Id is bound.
--
-- It is used for the following purposes:
-- a) for static forms in TcExpr.checkClosedInStaticForm and
-- b) to figure out when a nested binding can be generalised,
--    in TcBinds.decideGeneralisationPlan.
--
data IdBindingInfo -- See Note [Meaning of IdBindingInfo and ClosedTypeId]
    = NotLetBound
    | ClosedLet
    | NonClosedLet
         RhsNames        -- Used for (static e) checks only
         ClosedTypeId    -- Used for generalisation checks
                         -- and for (static e) checks

-- | IsGroupClosed describes a group of mutually-recursive bindings
data IsGroupClosed
  = IsGroupClosed
      (NameEnv RhsNames)  -- Free var info for the RHS of each binding in the goup
                          -- Used only for (static e) checks

      ClosedTypeId        -- True <=> all the free vars of the group are
                          --          imported or ClosedLet or
                          --          NonClosedLet with ClosedTypeId=True.
                          --          In particular, no tyvars, no NotLetBound

type RhsNames = NameSet   -- Names of variables, mentioned on the RHS of
                          -- a definition, that are not Global or ClosedLet

type ClosedTypeId = Bool
  -- See Note [Meaning of IdBindingInfo and ClosedTypeId]

{- Note [Meaning of IdBindingInfo]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
NotLetBound means that
  the Id is not let-bound (e.g. it is bound in a
  lambda-abstraction or in a case pattern)

ClosedLet means that
   - The Id is let-bound,
   - Any free term variables are also Global or ClosedLet
   - Its type has no free variables (NB: a top-level binding subject
     to the MR might have free vars in its type)
   These ClosedLets can definitely be floated to top level; and we
   may need to do so for static forms.

   Property:   ClosedLet
             is equivalent to
               NonClosedLet emptyNameSet True

(NonClosedLet (fvs::RhsNames) (cl::ClosedTypeId)) means that
   - The Id is let-bound

   - The fvs::RhsNames contains the free names of the RHS,
     excluding Global and ClosedLet ones.

   - For the ClosedTypeId field see Note [Bindings with closed types]

For (static e) to be valid, we need for every 'x' free in 'e',
that x's binding is floatable to the top level.  Specifically:
   * x's RhsNames must be empty
   * x's type has no free variables
See Note [Grand plan for static forms] in StaticPtrTable.hs.
This test is made in TcExpr.checkClosedInStaticForm.
Actually knowing x's RhsNames (rather than just its emptiness
or otherwise) is just so we can produce better error messages

Note [Bindings with closed types: ClosedTypeId]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Consider

  f x = let g ys = map not ys
        in ...

Can we generalise 'g' under the OutsideIn algorithm?  Yes,
because all g's free variables are top-level; that is they themselves
have no free type variables, and it is the type variables in the
environment that makes things tricky for OutsideIn generalisation.

Here's the invariant:
   If an Id has ClosedTypeId=True (in its IdBindingInfo), then
   the Id's type is /definitely/ closed (has no free type variables).
   Specifically,
       a) The Id's acutal type is closed (has no free tyvars)
       b) Either the Id has a (closed) user-supplied type signature
          or all its free variables are Global/ClosedLet
             or NonClosedLet with ClosedTypeId=True.
          In particular, none are NotLetBound.

Why is (b) needed?   Consider
    \x. (x :: Int, let y = x+1 in ...)
Initially x::alpha.  If we happen to typecheck the 'let' before the
(x::Int), y's type will have a free tyvar; but if the other way round
it won't.  So we treat any let-bound variable with a free
non-let-bound variable as not ClosedTypeId, regardless of what the
free vars of its type actually are.

But if it has a signature, all is well:
   \x. ...(let { y::Int; y = x+1 } in
           let { v = y+2 } in ...)...
Here the signature on 'v' makes 'y' a ClosedTypeId, so we can
generalise 'v'.

Note that:

  * A top-level binding may not have ClosedTypeId=True, if it suffers
    from the MR

  * A nested binding may be closed (eg 'g' in the example we started
    with). Indeed, that's the point; whether a function is defined at
    top level or nested is orthogonal to the question of whether or
    not it is closed.

  * A binding may be non-closed because it mentions a lexically scoped
    *type variable*  Eg
        f :: forall a. blah
        f x = let g y = ...(y::a)...

Under OutsideIn we are free to generalise an Id all of whose free
variables have ClosedTypeId=True (or imported).  This is an extension
compared to the JFP paper on OutsideIn, which used "top-level" as a
proxy for "closed".  (It's not a good proxy anyway -- the MR can make
a top-level binding with a free type variable.)

Note [Type variables in the type environment]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
The type environment has a binding for each lexically-scoped
type variable that is in scope.  For example

  f :: forall a. a -> a
  f x = (x :: a)

  g1 :: [a] -> a
  g1 (ys :: [b]) = head ys :: b

  g2 :: [Int] -> Int
  g2 (ys :: [c]) = head ys :: c

* The forall'd variable 'a' in the signature scopes over f's RHS.

* The pattern-bound type variable 'b' in 'g1' scopes over g1's
  RHS; note that it is bound to a skolem 'a' which is not itself
  lexically in scope.

* The pattern-bound type variable 'c' in 'g2' is bound to
  Int; that is, pattern-bound type variables can stand for
  arbitrary types. (see
    GHC proposal #128 "Allow ScopedTypeVariables to refer to types"
    https://github.com/ghc-proposals/ghc-proposals/pull/128,
  and the paper
    "Type variables in patterns", Haskell Symposium 2018.


This is implemented by the constructor
   ATyVar Name TcTyVar
in the type environment.

* The Name is the name of the original, lexically scoped type
  variable

* The TcTyVar is sometimes a skolem (like in 'f'), and sometimes
  a unification variable (like in 'g1', 'g2').  We never zonk the
  type environment so in the latter case it always stays as a
  unification variable, although that variable may be later
  unified with a type (such as Int in 'g2').
-}

instance Outputable IdBindingInfo where
  ppr :: IdBindingInfo -> SDoc
ppr NotLetBound = FilePath -> SDoc
text "NotLetBound"
  ppr ClosedLet = FilePath -> SDoc
text "TopLevelLet"
  ppr (NonClosedLet fvs :: NameSet
fvs closed_type :: Bool
closed_type) =
    FilePath -> SDoc
text "TopLevelLet" SDoc -> SDoc -> SDoc
<+> NameSet -> SDoc
forall a. Outputable a => a -> SDoc
ppr NameSet
fvs SDoc -> SDoc -> SDoc
<+> Bool -> SDoc
forall a. Outputable a => a -> SDoc
ppr Bool
closed_type

instance Outputable PromotionErr where
  ppr :: PromotionErr -> SDoc
ppr ClassPE                     = FilePath -> SDoc
text "ClassPE"
  ppr TyConPE                     = FilePath -> SDoc
text "TyConPE"
  ppr PatSynPE                    = FilePath -> SDoc
text "PatSynPE"
  ppr PatSynExPE                  = FilePath -> SDoc
text "PatSynExPE"
  ppr FamDataConPE                = FilePath -> SDoc
text "FamDataConPE"
  ppr (ConstrainedDataConPE pred :: Type
pred) = FilePath -> SDoc
text "ConstrainedDataConPE"
                                      SDoc -> SDoc -> SDoc
<+> SDoc -> SDoc
parens (Type -> SDoc
forall a. Outputable a => a -> SDoc
ppr Type
pred)
  ppr RecDataConPE                = FilePath -> SDoc
text "RecDataConPE"
  ppr NoDataKindsTC               = FilePath -> SDoc
text "NoDataKindsTC"
  ppr NoDataKindsDC               = FilePath -> SDoc
text "NoDataKindsDC"

pprTcTyThingCategory :: TcTyThing -> SDoc
pprTcTyThingCategory :: TcTyThing -> SDoc
pprTcTyThingCategory (AGlobal thing :: TyThing
thing)    = TyThing -> SDoc
pprTyThingCategory TyThing
thing
pprTcTyThingCategory (ATyVar {})        = FilePath -> SDoc
text "Type variable"
pprTcTyThingCategory (ATcId {})         = FilePath -> SDoc
text "Local identifier"
pprTcTyThingCategory (ATcTyCon {})     = FilePath -> SDoc
text "Local tycon"
pprTcTyThingCategory (APromotionErr pe :: PromotionErr
pe) = PromotionErr -> SDoc
pprPECategory PromotionErr
pe

pprPECategory :: PromotionErr -> SDoc
pprPECategory :: PromotionErr -> SDoc
pprPECategory ClassPE                = FilePath -> SDoc
text "Class"
pprPECategory TyConPE                = FilePath -> SDoc
text "Type constructor"
pprPECategory PatSynPE               = FilePath -> SDoc
text "Pattern synonym"
pprPECategory PatSynExPE             = FilePath -> SDoc
text "Pattern synonym existential"
pprPECategory FamDataConPE           = FilePath -> SDoc
text "Data constructor"
pprPECategory ConstrainedDataConPE{} = FilePath -> SDoc
text "Data constructor"
pprPECategory RecDataConPE           = FilePath -> SDoc
text "Data constructor"
pprPECategory NoDataKindsTC          = FilePath -> SDoc
text "Type constructor"
pprPECategory NoDataKindsDC          = FilePath -> SDoc
text "Data constructor"

{-
************************************************************************
*                                                                      *
        Operations over ImportAvails
*                                                                      *
************************************************************************
-}

-- | 'ImportAvails' summarises what was imported from where, irrespective of
-- whether the imported things are actually used or not.  It is used:
--
--  * when processing the export list,
--
--  * when constructing usage info for the interface file,
--
--  * to identify the list of directly imported modules for initialisation
--    purposes and for optimised overlap checking of family instances,
--
--  * when figuring out what things are really unused
--
data ImportAvails
   = ImportAvails {
        ImportAvails -> ImportedMods
imp_mods :: ImportedMods,
          --      = ModuleEnv [ImportedModsVal],
          -- ^ Domain is all directly-imported modules
          --
          -- See the documentation on ImportedModsVal in HscTypes for the
          -- meaning of the fields.
          --
          -- We need a full ModuleEnv rather than a ModuleNameEnv here,
          -- because we might be importing modules of the same name from
          -- different packages. (currently not the case, but might be in the
          -- future).

        ImportAvails -> ModuleNameEnv (ModuleName, Bool)
imp_dep_mods :: ModuleNameEnv (ModuleName, IsBootInterface),
          -- ^ Home-package modules needed by the module being compiled
          --
          -- It doesn't matter whether any of these dependencies
          -- are actually /used/ when compiling the module; they
          -- are listed if they are below it at all.  For
          -- example, suppose M imports A which imports X.  Then
          -- compiling M might not need to consult X.hi, but X
          -- is still listed in M's dependencies.

        ImportAvails -> Set InstalledUnitId
imp_dep_pkgs :: Set InstalledUnitId,
          -- ^ Packages needed by the module being compiled, whether directly,
          -- or via other modules in this package, or via modules imported
          -- from other packages.

        ImportAvails -> Set InstalledUnitId
imp_trust_pkgs :: Set InstalledUnitId,
          -- ^ This is strictly a subset of imp_dep_pkgs and records the
          -- packages the current module needs to trust for Safe Haskell
          -- compilation to succeed. A package is required to be trusted if
          -- we are dependent on a trustworthy module in that package.
          -- While perhaps making imp_dep_pkgs a tuple of (UnitId, Bool)
          -- where True for the bool indicates the package is required to be
          -- trusted is the more logical  design, doing so complicates a lot
          -- of code not concerned with Safe Haskell.
          -- See Note [RnNames . Tracking Trust Transitively]

        ImportAvails -> Bool
imp_trust_own_pkg :: Bool,
          -- ^ Do we require that our own package is trusted?
          -- This is to handle efficiently the case where a Safe module imports
          -- a Trustworthy module that resides in the same package as it.
          -- See Note [RnNames . Trust Own Package]

        ImportAvails -> [Module]
imp_orphs :: [Module],
          -- ^ Orphan modules below us in the import tree (and maybe including
          -- us for imported modules)

        ImportAvails -> [Module]
imp_finsts :: [Module]
          -- ^ Family instance modules below us in the import tree (and maybe
          -- including us for imported modules)
      }

mkModDeps :: [(ModuleName, IsBootInterface)]
          -> ModuleNameEnv (ModuleName, IsBootInterface)
mkModDeps :: [(ModuleName, Bool)] -> ModuleNameEnv (ModuleName, Bool)
mkModDeps deps :: [(ModuleName, Bool)]
deps = (ModuleNameEnv (ModuleName, Bool)
 -> (ModuleName, Bool) -> ModuleNameEnv (ModuleName, Bool))
-> ModuleNameEnv (ModuleName, Bool)
-> [(ModuleName, Bool)]
-> ModuleNameEnv (ModuleName, Bool)
forall (t :: * -> *) b a.
Foldable t =>
(b -> a -> b) -> b -> t a -> b
foldl' ModuleNameEnv (ModuleName, Bool)
-> (ModuleName, Bool) -> ModuleNameEnv (ModuleName, Bool)
forall key b.
Uniquable key =>
UniqFM (key, b) -> (key, b) -> UniqFM (key, b)
add ModuleNameEnv (ModuleName, Bool)
forall elt. UniqFM elt
emptyUFM [(ModuleName, Bool)]
deps
               where
                 add :: UniqFM (key, b) -> (key, b) -> UniqFM (key, b)
add env :: UniqFM (key, b)
env elt :: (key, b)
elt@(m :: key
m,_) = UniqFM (key, b) -> key -> (key, b) -> UniqFM (key, b)
forall key elt.
Uniquable key =>
UniqFM elt -> key -> elt -> UniqFM elt
addToUFM UniqFM (key, b)
env key
m (key, b)
elt

modDepsElts
  :: ModuleNameEnv (ModuleName, IsBootInterface)
  -> [(ModuleName, IsBootInterface)]
modDepsElts :: ModuleNameEnv (ModuleName, Bool) -> [(ModuleName, Bool)]
modDepsElts = [(ModuleName, Bool)] -> [(ModuleName, Bool)]
forall a. Ord a => [a] -> [a]
sort ([(ModuleName, Bool)] -> [(ModuleName, Bool)])
-> (ModuleNameEnv (ModuleName, Bool) -> [(ModuleName, Bool)])
-> ModuleNameEnv (ModuleName, Bool)
-> [(ModuleName, Bool)]
forall b c a. (b -> c) -> (a -> b) -> a -> c
. ModuleNameEnv (ModuleName, Bool) -> [(ModuleName, Bool)]
forall elt. UniqFM elt -> [elt]
nonDetEltsUFM
  -- It's OK to use nonDetEltsUFM here because sorting by module names
  -- restores determinism

emptyImportAvails :: ImportAvails
emptyImportAvails :: ImportAvails
emptyImportAvails = ImportAvails :: ImportedMods
-> ModuleNameEnv (ModuleName, Bool)
-> Set InstalledUnitId
-> Set InstalledUnitId
-> Bool
-> [Module]
-> [Module]
-> ImportAvails
ImportAvails { imp_mods :: ImportedMods
imp_mods          = ImportedMods
forall a. ModuleEnv a
emptyModuleEnv,
                                   imp_dep_mods :: ModuleNameEnv (ModuleName, Bool)
imp_dep_mods      = ModuleNameEnv (ModuleName, Bool)
forall elt. UniqFM elt
emptyUFM,
                                   imp_dep_pkgs :: Set InstalledUnitId
imp_dep_pkgs      = Set InstalledUnitId
forall a. Set a
S.empty,
                                   imp_trust_pkgs :: Set InstalledUnitId
imp_trust_pkgs    = Set InstalledUnitId
forall a. Set a
S.empty,
                                   imp_trust_own_pkg :: Bool
imp_trust_own_pkg = Bool
False,
                                   imp_orphs :: [Module]
imp_orphs         = [],
                                   imp_finsts :: [Module]
imp_finsts        = [] }

-- | Union two ImportAvails
--
-- This function is a key part of Import handling, basically
-- for each import we create a separate ImportAvails structure
-- and then union them all together with this function.
plusImportAvails ::  ImportAvails ->  ImportAvails ->  ImportAvails
plusImportAvails :: ImportAvails -> ImportAvails -> ImportAvails
plusImportAvails
  (ImportAvails { imp_mods :: ImportAvails -> ImportedMods
imp_mods = ImportedMods
mods1,
                  imp_dep_mods :: ImportAvails -> ModuleNameEnv (ModuleName, Bool)
imp_dep_mods = ModuleNameEnv (ModuleName, Bool)
dmods1, imp_dep_pkgs :: ImportAvails -> Set InstalledUnitId
imp_dep_pkgs = Set InstalledUnitId
dpkgs1,
                  imp_trust_pkgs :: ImportAvails -> Set InstalledUnitId
imp_trust_pkgs = Set InstalledUnitId
tpkgs1, imp_trust_own_pkg :: ImportAvails -> Bool
imp_trust_own_pkg = Bool
tself1,
                  imp_orphs :: ImportAvails -> [Module]
imp_orphs = [Module]
orphs1, imp_finsts :: ImportAvails -> [Module]
imp_finsts = [Module]
finsts1 })
  (ImportAvails { imp_mods :: ImportAvails -> ImportedMods
imp_mods = ImportedMods
mods2,
                  imp_dep_mods :: ImportAvails -> ModuleNameEnv (ModuleName, Bool)
imp_dep_mods = ModuleNameEnv (ModuleName, Bool)
dmods2, imp_dep_pkgs :: ImportAvails -> Set InstalledUnitId
imp_dep_pkgs = Set InstalledUnitId
dpkgs2,
                  imp_trust_pkgs :: ImportAvails -> Set InstalledUnitId
imp_trust_pkgs = Set InstalledUnitId
tpkgs2, imp_trust_own_pkg :: ImportAvails -> Bool
imp_trust_own_pkg = Bool
tself2,
                  imp_orphs :: ImportAvails -> [Module]
imp_orphs = [Module]
orphs2, imp_finsts :: ImportAvails -> [Module]
imp_finsts = [Module]
finsts2 })
  = ImportAvails :: ImportedMods
-> ModuleNameEnv (ModuleName, Bool)
-> Set InstalledUnitId
-> Set InstalledUnitId
-> Bool
-> [Module]
-> [Module]
-> ImportAvails
ImportAvails { imp_mods :: ImportedMods
imp_mods          = ([ImportedBy] -> [ImportedBy] -> [ImportedBy])
-> ImportedMods -> ImportedMods -> ImportedMods
forall a.
(a -> a -> a) -> ModuleEnv a -> ModuleEnv a -> ModuleEnv a
plusModuleEnv_C [ImportedBy] -> [ImportedBy] -> [ImportedBy]
forall a. [a] -> [a] -> [a]
(++) ImportedMods
mods1 ImportedMods
mods2,
                   imp_dep_mods :: ModuleNameEnv (ModuleName, Bool)
imp_dep_mods      = ((ModuleName, Bool) -> (ModuleName, Bool) -> (ModuleName, Bool))
-> ModuleNameEnv (ModuleName, Bool)
-> ModuleNameEnv (ModuleName, Bool)
-> ModuleNameEnv (ModuleName, Bool)
forall elt.
(elt -> elt -> elt) -> UniqFM elt -> UniqFM elt -> UniqFM elt
plusUFM_C (ModuleName, Bool) -> (ModuleName, Bool) -> (ModuleName, Bool)
forall a.
(Eq a, Outputable a) =>
(a, Bool) -> (a, Bool) -> (a, Bool)
plus_mod_dep ModuleNameEnv (ModuleName, Bool)
dmods1 ModuleNameEnv (ModuleName, Bool)
dmods2,
                   imp_dep_pkgs :: Set InstalledUnitId
imp_dep_pkgs      = Set InstalledUnitId
dpkgs1 Set InstalledUnitId -> Set InstalledUnitId -> Set InstalledUnitId
forall a. Ord a => Set a -> Set a -> Set a
`S.union` Set InstalledUnitId
dpkgs2,
                   imp_trust_pkgs :: Set InstalledUnitId
imp_trust_pkgs    = Set InstalledUnitId
tpkgs1 Set InstalledUnitId -> Set InstalledUnitId -> Set InstalledUnitId
forall a. Ord a => Set a -> Set a -> Set a
`S.union` Set InstalledUnitId
tpkgs2,
                   imp_trust_own_pkg :: Bool
imp_trust_own_pkg = Bool
tself1 Bool -> Bool -> Bool
|| Bool
tself2,
                   imp_orphs :: [Module]
imp_orphs         = [Module]
orphs1 [Module] -> [Module] -> [Module]
forall a. (Outputable a, Eq a) => [a] -> [a] -> [a]
`unionLists` [Module]
orphs2,
                   imp_finsts :: [Module]
imp_finsts        = [Module]
finsts1 [Module] -> [Module] -> [Module]
forall a. (Outputable a, Eq a) => [a] -> [a] -> [a]
`unionLists` [Module]
finsts2 }
  where
    plus_mod_dep :: (a, Bool) -> (a, Bool) -> (a, Bool)
plus_mod_dep r1 :: (a, Bool)
r1@(m1 :: a
m1, boot1 :: Bool
boot1) r2 :: (a, Bool)
r2@(m2 :: a
m2, boot2 :: Bool
boot2)
      | ASSERT2( m1 == m2, (ppr m1 <+> ppr m2) $$ (ppr boot1 <+> ppr boot2) )
        Bool
boot1 = (a, Bool)
r2
      | Bool
otherwise = (a, Bool)
r1
      -- If either side can "see" a non-hi-boot interface, use that
      -- Reusing existing tuples saves 10% of allocations on test
      -- perf/compiler/MultiLayerModules

{-
************************************************************************
*                                                                      *
\subsection{Where from}
*                                                                      *
************************************************************************

The @WhereFrom@ type controls where the renamer looks for an interface file
-}

data WhereFrom
  = ImportByUser IsBootInterface        -- Ordinary user import (perhaps {-# SOURCE #-})
  | ImportBySystem                      -- Non user import.
  | ImportByPlugin                      -- Importing a plugin;
                                        -- See Note [Care with plugin imports] in LoadIface

instance Outputable WhereFrom where
  ppr :: WhereFrom -> SDoc
ppr (ImportByUser is_boot :: Bool
is_boot) | Bool
is_boot     = FilePath -> SDoc
text "{- SOURCE -}"
                             | Bool
otherwise   = SDoc
empty
  ppr ImportBySystem                       = FilePath -> SDoc
text "{- SYSTEM -}"
  ppr ImportByPlugin                       = FilePath -> SDoc
text "{- PLUGIN -}"


{- *********************************************************************
*                                                                      *
                Type signatures
*                                                                      *
********************************************************************* -}

-- These data types need to be here only because
-- TcSimplify uses them, and TcSimplify is fairly
-- low down in the module hierarchy

type TcSigFun  = Name -> Maybe TcSigInfo

data TcSigInfo = TcIdSig     TcIdSigInfo
               | TcPatSynSig TcPatSynInfo

data TcIdSigInfo   -- See Note [Complete and partial type signatures]
  = CompleteSig    -- A complete signature with no wildcards,
                   -- so the complete polymorphic type is known.
      { TcIdSigInfo -> TyVar
sig_bndr :: TcId          -- The polymorphic Id with that type

      , TcIdSigInfo -> UserTypeCtxt
sig_ctxt :: UserTypeCtxt  -- In the case of type-class default methods,
                                  -- the Name in the FunSigCtxt is not the same
                                  -- as the TcId; the former is 'op', while the
                                  -- latter is '$dmop' or some such

      , TcIdSigInfo -> SrcSpan
sig_loc  :: SrcSpan       -- Location of the type signature
      }

  | PartialSig     -- A partial type signature (i.e. includes one or more
                   -- wildcards). In this case it doesn't make sense to give
                   -- the polymorphic Id, because we are going to /infer/ its
                   -- type, so we can't make the polymorphic Id ab-initio
      { TcIdSigInfo -> Name
psig_name  :: Name   -- Name of the function; used when report wildcards
      , TcIdSigInfo -> LHsSigWcType GhcRn
psig_hs_ty :: LHsSigWcType GhcRn  -- The original partial signature in
                                          -- HsSyn form
      , sig_ctxt   :: UserTypeCtxt
      , sig_loc    :: SrcSpan            -- Location of the type signature
      }


{- Note [Complete and partial type signatures]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
A type signature is partial when it contains one or more wildcards
(= type holes).  The wildcard can either be:
* A (type) wildcard occurring in sig_theta or sig_tau. These are
  stored in sig_wcs.
      f :: Bool -> _
      g :: Eq _a => _a -> _a -> Bool
* Or an extra-constraints wildcard, stored in sig_cts:
      h :: (Num a, _) => a -> a

A type signature is a complete type signature when there are no
wildcards in the type signature, i.e. iff sig_wcs is empty and
sig_extra_cts is Nothing.
-}

data TcIdSigInst
  = TISI { TcIdSigInst -> TcIdSigInfo
sig_inst_sig :: TcIdSigInfo

         , TcIdSigInst -> [(Name, TyVar)]
sig_inst_skols :: [(Name, TcTyVar)]
               -- Instantiated type and kind variables, TyVarTvs
               -- The Name is the Name that the renamer chose;
               --   but the TcTyVar may come from instantiating
               --   the type and hence have a different unique.
               -- No need to keep track of whether they are truly lexically
               --   scoped because the renamer has named them uniquely
               -- See Note [Binding scoped type variables] in TcSigs

         , TcIdSigInst -> [Type]
sig_inst_theta  :: TcThetaType
               -- Instantiated theta.  In the case of a
               -- PartialSig, sig_theta does not include
               -- the extra-constraints wildcard

         , TcIdSigInst -> Type
sig_inst_tau :: TcSigmaType   -- Instantiated tau
               -- See Note [sig_inst_tau may be polymorphic]

         -- Relevant for partial signature only
         , TcIdSigInst -> [(Name, TyVar)]
sig_inst_wcs   :: [(Name, TcTyVar)]
               -- Like sig_inst_skols, but for wildcards.  The named
               -- wildcards scope over the binding, and hence their
               -- Names may appear in type signatures in the binding

         , TcIdSigInst -> Maybe Type
sig_inst_wcx   :: Maybe TcType
               -- Extra-constraints wildcard to fill in, if any
               -- If this exists, it is surely of the form (meta_tv |> co)
               -- (where the co might be reflexive). This is filled in
               -- only from the return value of TcHsType.tcWildCardOcc
         }

{- Note [sig_inst_tau may be polymorphic]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Note that "sig_inst_tau" might actually be a polymorphic type,
if the original function had a signature like
   forall a. Eq a => forall b. Ord b => ....
But that's ok: tcMatchesFun (called by tcRhs) can deal with that
It happens, too!  See Note [Polymorphic methods] in TcClassDcl.

Note [Wildcards in partial signatures]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
The wildcards in psig_wcs may stand for a type mentioning
the universally-quantified tyvars of psig_ty

E.g.  f :: forall a. _ -> a
      f x = x
We get sig_inst_skols = [a]
       sig_inst_tau   = _22 -> a
       sig_inst_wcs   = [_22]
and _22 in the end is unified with the type 'a'

Moreover the kind of a wildcard in sig_inst_wcs may mention
the universally-quantified tyvars sig_inst_skols
e.g.   f :: t a -> t _
Here we get
   sig_inst_skols = [k:*, (t::k ->*), (a::k)]
   sig_inst_tau   = t a -> t _22
   sig_inst_wcs   = [ _22::k ]
-}

data TcPatSynInfo
  = TPSI {
        TcPatSynInfo -> Name
patsig_name           :: Name,
        TcPatSynInfo -> [TyVarBinder]
patsig_implicit_bndrs :: [TyVarBinder], -- Implicitly-bound kind vars (Inferred) and
                                                -- implicitly-bound type vars (Specified)
          -- See Note [The pattern-synonym signature splitting rule] in TcPatSyn
        TcPatSynInfo -> [TyVar]
patsig_univ_bndrs     :: [TyVar],       -- Bound by explicit user forall
        TcPatSynInfo -> [Type]
patsig_req            :: TcThetaType,
        TcPatSynInfo -> [TyVar]
patsig_ex_bndrs       :: [TyVar],       -- Bound by explicit user forall
        TcPatSynInfo -> [Type]
patsig_prov           :: TcThetaType,
        TcPatSynInfo -> Type
patsig_body_ty        :: TcSigmaType
    }

instance Outputable TcSigInfo where
  ppr :: TcSigInfo -> SDoc
ppr (TcIdSig     idsi :: TcIdSigInfo
idsi) = TcIdSigInfo -> SDoc
forall a. Outputable a => a -> SDoc
ppr TcIdSigInfo
idsi
  ppr (TcPatSynSig tpsi :: TcPatSynInfo
tpsi) = FilePath -> SDoc
text "TcPatSynInfo" SDoc -> SDoc -> SDoc
<+> TcPatSynInfo -> SDoc
forall a. Outputable a => a -> SDoc
ppr TcPatSynInfo
tpsi

instance Outputable TcIdSigInfo where
    ppr :: TcIdSigInfo -> SDoc
ppr (CompleteSig { sig_bndr :: TcIdSigInfo -> TyVar
sig_bndr = TyVar
bndr })
        = TyVar -> SDoc
forall a. Outputable a => a -> SDoc
ppr TyVar
bndr SDoc -> SDoc -> SDoc
<+> SDoc
dcolon SDoc -> SDoc -> SDoc
<+> Type -> SDoc
forall a. Outputable a => a -> SDoc
ppr (TyVar -> Type
idType TyVar
bndr)
    ppr (PartialSig { psig_name :: TcIdSigInfo -> Name
psig_name = Name
name, psig_hs_ty :: TcIdSigInfo -> LHsSigWcType GhcRn
psig_hs_ty = LHsSigWcType GhcRn
hs_ty })
        = FilePath -> SDoc
text "psig" SDoc -> SDoc -> SDoc
<+> Name -> SDoc
forall a. Outputable a => a -> SDoc
ppr Name
name SDoc -> SDoc -> SDoc
<+> SDoc
dcolon SDoc -> SDoc -> SDoc
<+> LHsSigWcType GhcRn -> SDoc
forall a. Outputable a => a -> SDoc
ppr LHsSigWcType GhcRn
hs_ty

instance Outputable TcIdSigInst where
    ppr :: TcIdSigInst -> SDoc
ppr (TISI { sig_inst_sig :: TcIdSigInst -> TcIdSigInfo
sig_inst_sig = TcIdSigInfo
sig, sig_inst_skols :: TcIdSigInst -> [(Name, TyVar)]
sig_inst_skols = [(Name, TyVar)]
skols
              , sig_inst_theta :: TcIdSigInst -> [Type]
sig_inst_theta = [Type]
theta, sig_inst_tau :: TcIdSigInst -> Type
sig_inst_tau = Type
tau })
        = SDoc -> Int -> SDoc -> SDoc
hang (TcIdSigInfo -> SDoc
forall a. Outputable a => a -> SDoc
ppr TcIdSigInfo
sig) 2 ([SDoc] -> SDoc
vcat [ [(Name, TyVar)] -> SDoc
forall a. Outputable a => a -> SDoc
ppr [(Name, TyVar)]
skols, [Type] -> SDoc
forall a. Outputable a => a -> SDoc
ppr [Type]
theta SDoc -> SDoc -> SDoc
<+> SDoc
darrow SDoc -> SDoc -> SDoc
<+> Type -> SDoc
forall a. Outputable a => a -> SDoc
ppr Type
tau ])

instance Outputable TcPatSynInfo where
    ppr :: TcPatSynInfo -> SDoc
ppr (TPSI{ patsig_name :: TcPatSynInfo -> Name
patsig_name = Name
name}) = Name -> SDoc
forall a. Outputable a => a -> SDoc
ppr Name
name

isPartialSig :: TcIdSigInst -> Bool
isPartialSig :: TcIdSigInst -> Bool
isPartialSig (TISI { sig_inst_sig :: TcIdSigInst -> TcIdSigInfo
sig_inst_sig = PartialSig {} }) = Bool
True
isPartialSig _                                       = Bool
False

-- | No signature or a partial signature
hasCompleteSig :: TcSigFun -> Name -> Bool
hasCompleteSig :: TcSigFun -> Name -> Bool
hasCompleteSig sig_fn :: TcSigFun
sig_fn name :: Name
name
  = case TcSigFun
sig_fn Name
name of
      Just (TcIdSig (CompleteSig {})) -> Bool
True
      _                               -> Bool
False


{-
************************************************************************
*                                                                      *
*                       Canonical constraints                          *
*                                                                      *
*   These are the constraints the low-level simplifier works with      *
*                                                                      *
************************************************************************
-}

-- The syntax of xi (ξ) types:
-- xi ::= a | T xis | xis -> xis | ... | forall a. tau
-- Two important notes:
--      (i) No type families, unless we are under a ForAll
--      (ii) Note that xi types can contain unexpanded type synonyms;
--           however, the (transitive) expansions of those type synonyms
--           will not contain any type functions, unless we are under a ForAll.
-- We enforce the structure of Xi types when we flatten (TcCanonical)

type Xi = Type       -- In many comments, "xi" ranges over Xi

type Cts = Bag Ct

data Ct
  -- Atomic canonical constraints
  = CDictCan {  -- e.g.  Num xi
      Ct -> CtEvidence
cc_ev     :: CtEvidence, -- See Note [Ct/evidence invariant]

      Ct -> Class
cc_class  :: Class,
      Ct -> [Type]
cc_tyargs :: [Xi],   -- cc_tyargs are function-free, hence Xi

      Ct -> Bool
cc_pend_sc :: Bool   -- See Note [The superclass story] in TcCanonical
                           -- True <=> (a) cc_class has superclasses
                           --          (b) we have not (yet) added those
                           --              superclasses as Givens
    }

  | CIrredCan {  -- These stand for yet-unusable predicates
      cc_ev    :: CtEvidence,   -- See Note [Ct/evidence invariant]
      Ct -> Bool
cc_insol :: Bool   -- True  <=> definitely an error, can never be solved
                         -- False <=> might be soluble

        -- For the might-be-soluble case, the ctev_pred of the evidence is
        -- of form   (tv xi1 xi2 ... xin)   with a tyvar at the head
        --      or   (tv1 ~ ty2)   where the CTyEqCan  kind invariant fails
        --      or   (F tys ~ ty)  where the CFunEqCan kind invariant fails
        -- See Note [CIrredCan constraints]

        -- The definitely-insoluble case is for things like
        --    Int ~ Bool      tycons don't match
        --    a ~ [a]         occurs check
    }

  | CTyEqCan {  -- tv ~ rhs
       -- Invariants:
       --   * See Note [Applying the inert substitution] in TcFlatten
       --   * tv not in tvs(rhs)   (occurs check)
       --   * If tv is a TauTv, then rhs has no foralls
       --       (this avoids substituting a forall for the tyvar in other types)
       --   * tcTypeKind ty `tcEqKind` tcTypeKind tv; Note [Ct kind invariant]
       --   * rhs may have at most one top-level cast
       --   * rhs (perhaps under the one cast) is not necessarily function-free,
       --       but it has no top-level function.
       --     E.g. a ~ [F b]  is fine
       --     but  a ~ F b    is not
       --   * If the equality is representational, rhs has no top-level newtype
       --     See Note [No top-level newtypes on RHS of representational
       --     equalities] in TcCanonical
       --   * If rhs (perhaps under the cast) is also a tv, then it is oriented
       --     to give best chance of
       --     unification happening; eg if rhs is touchable then lhs is too
      cc_ev     :: CtEvidence, -- See Note [Ct/evidence invariant]
      Ct -> TyVar
cc_tyvar  :: TcTyVar,
      Ct -> Type
cc_rhs    :: TcType,     -- Not necessarily function-free (hence not Xi)
                               -- See invariants above

      Ct -> EqRel
cc_eq_rel :: EqRel       -- INVARIANT: cc_eq_rel = ctEvEqRel cc_ev
    }

  | CFunEqCan {  -- F xis ~ fsk
       -- Invariants:
       --   * isTypeFamilyTyCon cc_fun
       --   * tcTypeKind (F xis) = tyVarKind fsk; Note [Ct kind invariant]
       --   * always Nominal role
      cc_ev     :: CtEvidence,  -- See Note [Ct/evidence invariant]
      Ct -> TyCon
cc_fun    :: TyCon,       -- A type function

      cc_tyargs :: [Xi],        -- cc_tyargs are function-free (hence Xi)
        -- Either under-saturated or exactly saturated
        --    *never* over-saturated (because if so
        --    we should have decomposed)

      Ct -> TyVar
cc_fsk    :: TcTyVar  -- [G]  always a FlatSkolTv
                            -- [W], [WD], or [D] always a FlatMetaTv
        -- See Note [The flattening story] in TcFlatten
    }

  | CNonCanonical {        -- See Note [NonCanonical Semantics] in TcSMonad
      cc_ev  :: CtEvidence
    }

  | CHoleCan {             -- See Note [Hole constraints]
       -- Treated as an "insoluble" constraint
       -- See Note [Insoluble constraints]
      cc_ev   :: CtEvidence,
      Ct -> Hole
cc_hole :: Hole
    }

  | CQuantCan QCInst       -- A quantified constraint
      -- NB: I expect to make more of the cases in Ct
      --     look like this, with the payload in an
      --     auxiliary type

------------
data QCInst  -- A much simplified version of ClsInst
             -- See Note [Quantified constraints] in TcCanonical
  = QCI { QCInst -> CtEvidence
qci_ev   :: CtEvidence -- Always of type forall tvs. context => ty
                                 -- Always Given
        , QCInst -> [TyVar]
qci_tvs  :: [TcTyVar]  -- The tvs
        , QCInst -> Type
qci_pred :: TcPredType -- The ty
        , QCInst -> Bool
qci_pend_sc :: Bool    -- Same as cc_pend_sc flag in CDictCan
                                 -- Invariant: True => qci_pred is a ClassPred
    }

instance Outputable QCInst where
  ppr :: QCInst -> SDoc
ppr (QCI { qci_ev :: QCInst -> CtEvidence
qci_ev = CtEvidence
ev }) = CtEvidence -> SDoc
forall a. Outputable a => a -> SDoc
ppr CtEvidence
ev

------------
-- | An expression or type hole
data Hole = ExprHole UnboundVar
            -- ^ Either an out-of-scope variable or a "true" hole in an
            -- expression (TypedHoles)
          | TypeHole OccName
            -- ^ A hole in a type (PartialTypeSignatures)

instance Outputable Hole where
  ppr :: Hole -> SDoc
ppr (ExprHole ub :: UnboundVar
ub)  = UnboundVar -> SDoc
forall a. Outputable a => a -> SDoc
ppr UnboundVar
ub
  ppr (TypeHole occ :: OccName
occ) = FilePath -> SDoc
text "TypeHole" SDoc -> SDoc -> SDoc
<> SDoc -> SDoc
parens (OccName -> SDoc
forall a. Outputable a => a -> SDoc
ppr OccName
occ)

holeOcc :: Hole -> OccName
holeOcc :: Hole -> OccName
holeOcc (ExprHole uv :: UnboundVar
uv)  = UnboundVar -> OccName
unboundVarOcc UnboundVar
uv
holeOcc (TypeHole occ :: OccName
occ) = OccName
occ

{- Note [Hole constraints]
~~~~~~~~~~~~~~~~~~~~~~~~~~
CHoleCan constraints are used for two kinds of holes,
distinguished by cc_hole:

  * For holes in expressions (including variables not in scope)
    e.g.   f x = g _ x

  * For holes in type signatures
    e.g.   f :: _ -> _
           f x = [x,True]

Note [CIrredCan constraints]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
CIrredCan constraints are used for constraints that are "stuck"
   - we can't solve them (yet)
   - we can't use them to solve other constraints
   - but they may become soluble if we substitute for some
     of the type variables in the constraint

Example 1:  (c Int), where c :: * -> Constraint.  We can't do anything
            with this yet, but if later c := Num, *then* we can solve it

Example 2:  a ~ b, where a :: *, b :: k, where k is a kind variable
            We don't want to use this to substitute 'b' for 'a', in case
            'k' is subsequently unifed with (say) *->*, because then
            we'd have ill-kinded types floating about.  Rather we want
            to defer using the equality altogether until 'k' get resolved.

Note [Ct/evidence invariant]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~
If  ct :: Ct, then extra fields of 'ct' cache precisely the ctev_pred field
of (cc_ev ct), and is fully rewritten wrt the substitution.   Eg for CDictCan,
   ctev_pred (cc_ev ct) = (cc_class ct) (cc_tyargs ct)
This holds by construction; look at the unique place where CDictCan is
built (in TcCanonical).

In contrast, the type of the evidence *term* (ctev_dest / ctev_evar) in
the evidence may *not* be fully zonked; we are careful not to look at it
during constraint solving. See Note [Evidence field of CtEvidence].

Note [Ct kind invariant]
~~~~~~~~~~~~~~~~~~~~~~~~
CTyEqCan and CFunEqCan both require that the kind of the lhs matches the kind
of the rhs. This is necessary because both constraints are used for substitutions
during solving. If the kinds differed, then the substitution would take a well-kinded
type to an ill-kinded one.

-}

mkNonCanonical :: CtEvidence -> Ct
mkNonCanonical :: CtEvidence -> Ct
mkNonCanonical ev :: CtEvidence
ev = CNonCanonical :: CtEvidence -> Ct
CNonCanonical { cc_ev :: CtEvidence
cc_ev = CtEvidence
ev }

mkNonCanonicalCt :: Ct -> Ct
mkNonCanonicalCt :: Ct -> Ct
mkNonCanonicalCt ct :: Ct
ct = CNonCanonical :: CtEvidence -> Ct
CNonCanonical { cc_ev :: CtEvidence
cc_ev = Ct -> CtEvidence
cc_ev Ct
ct }

mkIrredCt :: CtEvidence -> Ct
mkIrredCt :: CtEvidence -> Ct
mkIrredCt ev :: CtEvidence
ev = CIrredCan :: CtEvidence -> Bool -> Ct
CIrredCan { cc_ev :: CtEvidence
cc_ev = CtEvidence
ev, cc_insol :: Bool
cc_insol = Bool
False }

mkInsolubleCt :: CtEvidence -> Ct
mkInsolubleCt :: CtEvidence -> Ct
mkInsolubleCt ev :: CtEvidence
ev = CIrredCan :: CtEvidence -> Bool -> Ct
CIrredCan { cc_ev :: CtEvidence
cc_ev = CtEvidence
ev, cc_insol :: Bool
cc_insol = Bool
True }

mkGivens :: CtLoc -> [EvId] -> [Ct]
mkGivens :: CtLoc -> [TyVar] -> [Ct]
mkGivens loc :: CtLoc
loc ev_ids :: [TyVar]
ev_ids
  = (TyVar -> Ct) -> [TyVar] -> [Ct]
forall a b. (a -> b) -> [a] -> [b]
map TyVar -> Ct
mk [TyVar]
ev_ids
  where
    mk :: TyVar -> Ct
mk ev_id :: TyVar
ev_id = CtEvidence -> Ct
mkNonCanonical (CtGiven :: Type -> TyVar -> CtLoc -> CtEvidence
CtGiven { ctev_evar :: TyVar
ctev_evar = TyVar
ev_id
                                       , ctev_pred :: Type
ctev_pred = TyVar -> Type
evVarPred TyVar
ev_id
                                       , ctev_loc :: CtLoc
ctev_loc = CtLoc
loc })

ctEvidence :: Ct -> CtEvidence
ctEvidence :: Ct -> CtEvidence
ctEvidence (CQuantCan (QCI { qci_ev :: QCInst -> CtEvidence
qci_ev = CtEvidence
ev })) = CtEvidence
ev
ctEvidence ct :: Ct
ct = Ct -> CtEvidence
cc_ev Ct
ct

ctLoc :: Ct -> CtLoc
ctLoc :: Ct -> CtLoc
ctLoc = CtEvidence -> CtLoc
ctEvLoc (CtEvidence -> CtLoc) -> (Ct -> CtEvidence) -> Ct -> CtLoc
forall b c a. (b -> c) -> (a -> b) -> a -> c
. Ct -> CtEvidence
ctEvidence

setCtLoc :: Ct -> CtLoc -> Ct
setCtLoc :: Ct -> CtLoc -> Ct
setCtLoc ct :: Ct
ct loc :: CtLoc
loc = Ct
ct { cc_ev :: CtEvidence
cc_ev = (Ct -> CtEvidence
cc_ev Ct
ct) { ctev_loc :: CtLoc
ctev_loc = CtLoc
loc } }

ctOrigin :: Ct -> CtOrigin
ctOrigin :: Ct -> CtOrigin
ctOrigin = CtLoc -> CtOrigin
ctLocOrigin (CtLoc -> CtOrigin) -> (Ct -> CtLoc) -> Ct -> CtOrigin
forall b c a. (b -> c) -> (a -> b) -> a -> c
. Ct -> CtLoc
ctLoc

ctPred :: Ct -> PredType
-- See Note [Ct/evidence invariant]
ctPred :: Ct -> Type
ctPred ct :: Ct
ct = CtEvidence -> Type
ctEvPred (Ct -> CtEvidence
ctEvidence Ct
ct)

ctEvId :: Ct -> EvVar
-- The evidence Id for this Ct
ctEvId :: Ct -> TyVar
ctEvId ct :: Ct
ct = CtEvidence -> TyVar
ctEvEvId (Ct -> CtEvidence
ctEvidence Ct
ct)

-- | Makes a new equality predicate with the same role as the given
-- evidence.
mkTcEqPredLikeEv :: CtEvidence -> TcType -> TcType -> TcType
mkTcEqPredLikeEv :: CtEvidence -> Type -> Type -> Type
mkTcEqPredLikeEv ev :: CtEvidence
ev
  = case Type -> EqRel
predTypeEqRel Type
pred of
      NomEq  -> Type -> Type -> Type
mkPrimEqPred
      ReprEq -> Type -> Type -> Type
mkReprPrimEqPred
  where
    pred :: Type
pred = CtEvidence -> Type
ctEvPred CtEvidence
ev

-- | Get the flavour of the given 'Ct'
ctFlavour :: Ct -> CtFlavour
ctFlavour :: Ct -> CtFlavour
ctFlavour = CtEvidence -> CtFlavour
ctEvFlavour (CtEvidence -> CtFlavour) -> (Ct -> CtEvidence) -> Ct -> CtFlavour
forall b c a. (b -> c) -> (a -> b) -> a -> c
. Ct -> CtEvidence
ctEvidence

-- | Get the equality relation for the given 'Ct'
ctEqRel :: Ct -> EqRel
ctEqRel :: Ct -> EqRel
ctEqRel = CtEvidence -> EqRel
ctEvEqRel (CtEvidence -> EqRel) -> (Ct -> CtEvidence) -> Ct -> EqRel
forall b c a. (b -> c) -> (a -> b) -> a -> c
. Ct -> CtEvidence
ctEvidence

instance Outputable Ct where
  ppr :: Ct -> SDoc
ppr ct :: Ct
ct = CtEvidence -> SDoc
forall a. Outputable a => a -> SDoc
ppr (Ct -> CtEvidence
ctEvidence Ct
ct) SDoc -> SDoc -> SDoc
<+> SDoc -> SDoc
parens SDoc
pp_sort
    where
      pp_sort :: SDoc
pp_sort = case Ct
ct of
         CTyEqCan {}      -> FilePath -> SDoc
text "CTyEqCan"
         CFunEqCan {}     -> FilePath -> SDoc
text "CFunEqCan"
         CNonCanonical {} -> FilePath -> SDoc
text "CNonCanonical"
         CDictCan { cc_pend_sc :: Ct -> Bool
cc_pend_sc = Bool
pend_sc }
            | Bool
pend_sc   -> FilePath -> SDoc
text "CDictCan(psc)"
            | Bool
otherwise -> FilePath -> SDoc
text "CDictCan"
         CIrredCan { cc_insol :: Ct -> Bool
cc_insol = Bool
insol }
            | Bool
insol     -> FilePath -> SDoc
text "CIrredCan(insol)"
            | Bool
otherwise -> FilePath -> SDoc
text "CIrredCan(sol)"
         CHoleCan { cc_hole :: Ct -> Hole
cc_hole = Hole
hole } -> FilePath -> SDoc
text "CHoleCan:" SDoc -> SDoc -> SDoc
<+> Hole -> SDoc
forall a. Outputable a => a -> SDoc
ppr Hole
hole
         CQuantCan (QCI { qci_pend_sc :: QCInst -> Bool
qci_pend_sc = Bool
pend_sc })
            | Bool
pend_sc   -> FilePath -> SDoc
text "CQuantCan(psc)"
            | Bool
otherwise -> FilePath -> SDoc
text "CQuantCan"

{-
************************************************************************
*                                                                      *
        Simple functions over evidence variables
*                                                                      *
************************************************************************
-}

---------------- Getting free tyvars -------------------------

-- | Returns free variables of constraints as a non-deterministic set
tyCoVarsOfCt :: Ct -> TcTyCoVarSet
tyCoVarsOfCt :: Ct -> TcTyVarSet
tyCoVarsOfCt = FV -> TcTyVarSet
fvVarSet (FV -> TcTyVarSet) -> (Ct -> FV) -> Ct -> TcTyVarSet
forall b c a. (b -> c) -> (a -> b) -> a -> c
. Ct -> FV
tyCoFVsOfCt

-- | Returns free variables of constraints as a deterministically ordered.
-- list. See Note [Deterministic FV] in FV.
tyCoVarsOfCtList :: Ct -> [TcTyCoVar]
tyCoVarsOfCtList :: Ct -> [TyVar]
tyCoVarsOfCtList = FV -> [TyVar]
fvVarList (FV -> [TyVar]) -> (Ct -> FV) -> Ct -> [TyVar]
forall b c a. (b -> c) -> (a -> b) -> a -> c
. Ct -> FV
tyCoFVsOfCt

-- | Returns free variables of constraints as a composable FV computation.
-- See Note [Deterministic FV] in FV.
tyCoFVsOfCt :: Ct -> FV
tyCoFVsOfCt :: Ct -> FV
tyCoFVsOfCt (CTyEqCan { cc_tyvar :: Ct -> TyVar
cc_tyvar = TyVar
tv, cc_rhs :: Ct -> Type
cc_rhs = Type
xi })
  = Type -> FV
tyCoFVsOfType Type
xi FV -> FV -> FV
`unionFV` TyVar -> FV
FV.unitFV TyVar
tv
                     FV -> FV -> FV
`unionFV` Type -> FV
tyCoFVsOfType (TyVar -> Type
tyVarKind TyVar
tv)
tyCoFVsOfCt (CFunEqCan { cc_tyargs :: Ct -> [Type]
cc_tyargs = [Type]
tys, cc_fsk :: Ct -> TyVar
cc_fsk = TyVar
fsk })
  = [Type] -> FV
tyCoFVsOfTypes [Type]
tys FV -> FV -> FV
`unionFV` TyVar -> FV
FV.unitFV TyVar
fsk
                       FV -> FV -> FV
`unionFV` Type -> FV
tyCoFVsOfType (TyVar -> Type
tyVarKind TyVar
fsk)
tyCoFVsOfCt (CDictCan { cc_tyargs :: Ct -> [Type]
cc_tyargs = [Type]
tys }) = [Type] -> FV
tyCoFVsOfTypes [Type]
tys
tyCoFVsOfCt ct :: Ct
ct = Type -> FV
tyCoFVsOfType (Ct -> Type
ctPred Ct
ct)

-- | Returns free variables of a bag of constraints as a non-deterministic
-- set. See Note [Deterministic FV] in FV.
tyCoVarsOfCts :: Cts -> TcTyCoVarSet
tyCoVarsOfCts :: Cts -> TcTyVarSet
tyCoVarsOfCts = FV -> TcTyVarSet
fvVarSet (FV -> TcTyVarSet) -> (Cts -> FV) -> Cts -> TcTyVarSet
forall b c a. (b -> c) -> (a -> b) -> a -> c
. Cts -> FV
tyCoFVsOfCts

-- | Returns free variables of a bag of constraints as a deterministically
-- odered list. See Note [Deterministic FV] in FV.
tyCoVarsOfCtsList :: Cts -> [TcTyCoVar]
tyCoVarsOfCtsList :: Cts -> [TyVar]
tyCoVarsOfCtsList = FV -> [TyVar]
fvVarList (FV -> [TyVar]) -> (Cts -> FV) -> Cts -> [TyVar]
forall b c a. (b -> c) -> (a -> b) -> a -> c
. Cts -> FV
tyCoFVsOfCts

-- | Returns free variables of a bag of constraints as a composable FV
-- computation. See Note [Deterministic FV] in FV.
tyCoFVsOfCts :: Cts -> FV
tyCoFVsOfCts :: Cts -> FV
tyCoFVsOfCts = (Ct -> FV -> FV) -> FV -> Cts -> FV
forall a r. (a -> r -> r) -> r -> Bag a -> r
foldrBag (FV -> FV -> FV
unionFV (FV -> FV -> FV) -> (Ct -> FV) -> Ct -> FV -> FV
forall b c a. (b -> c) -> (a -> b) -> a -> c
. Ct -> FV
tyCoFVsOfCt) FV
emptyFV

-- | Returns free variables of WantedConstraints as a non-deterministic
-- set. See Note [Deterministic FV] in FV.
tyCoVarsOfWC :: WantedConstraints -> TyCoVarSet
-- Only called on *zonked* things, hence no need to worry about flatten-skolems
tyCoVarsOfWC :: WantedConstraints -> TcTyVarSet
tyCoVarsOfWC = FV -> TcTyVarSet
fvVarSet (FV -> TcTyVarSet)
-> (WantedConstraints -> FV) -> WantedConstraints -> TcTyVarSet
forall b c a. (b -> c) -> (a -> b) -> a -> c
. WantedConstraints -> FV
tyCoFVsOfWC

-- | Returns free variables of WantedConstraints as a deterministically
-- ordered list. See Note [Deterministic FV] in FV.
tyCoVarsOfWCList :: WantedConstraints -> [TyCoVar]
-- Only called on *zonked* things, hence no need to worry about flatten-skolems
tyCoVarsOfWCList :: WantedConstraints -> [TyVar]
tyCoVarsOfWCList = FV -> [TyVar]
fvVarList (FV -> [TyVar])
-> (WantedConstraints -> FV) -> WantedConstraints -> [TyVar]
forall b c a. (b -> c) -> (a -> b) -> a -> c
. WantedConstraints -> FV
tyCoFVsOfWC

-- | Returns free variables of WantedConstraints as a composable FV
-- computation. See Note [Deterministic FV] in FV.
tyCoFVsOfWC :: WantedConstraints -> FV
-- Only called on *zonked* things, hence no need to worry about flatten-skolems
tyCoFVsOfWC :: WantedConstraints -> FV
tyCoFVsOfWC (WC { wc_simple :: WantedConstraints -> Cts
wc_simple = Cts
simple, wc_impl :: WantedConstraints -> Bag Implication
wc_impl = Bag Implication
implic })
  = Cts -> FV
tyCoFVsOfCts Cts
simple FV -> FV -> FV
`unionFV`
    (Implication -> FV) -> Bag Implication -> FV
forall a. (a -> FV) -> Bag a -> FV
tyCoFVsOfBag Implication -> FV
tyCoFVsOfImplic Bag Implication
implic

-- | Returns free variables of Implication as a composable FV computation.
-- See Note [Deterministic FV] in FV.
tyCoFVsOfImplic :: Implication -> FV
-- Only called on *zonked* things, hence no need to worry about flatten-skolems
tyCoFVsOfImplic :: Implication -> FV
tyCoFVsOfImplic (Implic { ic_skols :: Implication -> [TyVar]
ic_skols = [TyVar]
skols
                        , ic_given :: Implication -> [TyVar]
ic_given = [TyVar]
givens
                        , ic_wanted :: Implication -> WantedConstraints
ic_wanted = WantedConstraints
wanted })
  | WantedConstraints -> Bool
isEmptyWC WantedConstraints
wanted
  = FV
emptyFV
  | Bool
otherwise
  = [TyVar] -> FV -> FV
tyCoFVsVarBndrs [TyVar]
skols  (FV -> FV) -> FV -> FV
forall a b. (a -> b) -> a -> b
$
    [TyVar] -> FV -> FV
tyCoFVsVarBndrs [TyVar]
givens (FV -> FV) -> FV -> FV
forall a b. (a -> b) -> a -> b
$
    WantedConstraints -> FV
tyCoFVsOfWC WantedConstraints
wanted

tyCoFVsOfBag :: (a -> FV) -> Bag a -> FV
tyCoFVsOfBag :: (a -> FV) -> Bag a -> FV
tyCoFVsOfBag tvs_of :: a -> FV
tvs_of = (a -> FV -> FV) -> FV -> Bag a -> FV
forall a r. (a -> r -> r) -> r -> Bag a -> r
foldrBag (FV -> FV -> FV
unionFV (FV -> FV -> FV) -> (a -> FV) -> a -> FV -> FV
forall b c a. (b -> c) -> (a -> b) -> a -> c
. a -> FV
tvs_of) FV
emptyFV

---------------------------
dropDerivedWC :: WantedConstraints -> WantedConstraints
-- See Note [Dropping derived constraints]
dropDerivedWC :: WantedConstraints -> WantedConstraints
dropDerivedWC wc :: WantedConstraints
wc@(WC { wc_simple :: WantedConstraints -> Cts
wc_simple = Cts
simples })
  = WantedConstraints
wc { wc_simple :: Cts
wc_simple = Cts -> Cts
dropDerivedSimples Cts
simples }
    -- The wc_impl implications are already (recursively) filtered

--------------------------
dropDerivedSimples :: Cts -> Cts
-- Drop all Derived constraints, but make [W] back into [WD],
-- so that if we re-simplify these constraints we will get all
-- the right derived constraints re-generated.  Forgetting this
-- step led to #12936
dropDerivedSimples :: Cts -> Cts
dropDerivedSimples simples :: Cts
simples = (Ct -> Maybe Ct) -> Cts -> Cts
forall a b. (a -> Maybe b) -> Bag a -> Bag b
mapMaybeBag Ct -> Maybe Ct
dropDerivedCt Cts
simples

dropDerivedCt :: Ct -> Maybe Ct
dropDerivedCt :: Ct -> Maybe Ct
dropDerivedCt ct :: Ct
ct
  = case CtEvidence -> CtFlavour
ctEvFlavour CtEvidence
ev of
      Wanted WOnly -> Ct -> Maybe Ct
forall a. a -> Maybe a
Just (Ct
ct' { cc_ev :: CtEvidence
cc_ev = CtEvidence
ev_wd })
      Wanted _     -> Ct -> Maybe Ct
forall a. a -> Maybe a
Just Ct
ct'
      _ | Ct -> Bool
isDroppableCt Ct
ct -> Maybe Ct
forall a. Maybe a
Nothing
        | Bool
otherwise        -> Ct -> Maybe Ct
forall a. a -> Maybe a
Just Ct
ct
  where
    ev :: CtEvidence
ev    = Ct -> CtEvidence
ctEvidence Ct
ct
    ev_wd :: CtEvidence
ev_wd = CtEvidence
ev { ctev_nosh :: ShadowInfo
ctev_nosh = ShadowInfo
WDeriv }
    ct' :: Ct
ct'   = Ct -> Ct
setPendingScDict Ct
ct -- See Note [Resetting cc_pend_sc]

{- Note [Resetting cc_pend_sc]
~~~~~~~~~~~~~~~~~~~~~~~~~~~
When we discard Derived constraints, in dropDerivedSimples, we must
set the cc_pend_sc flag to True, so that if we re-process this
CDictCan we will re-generate its derived superclasses. Otherwise
we might miss some fundeps.  Trac #13662 showed this up.

See Note [The superclass story] in TcCanonical.
-}

isDroppableCt :: Ct -> Bool
isDroppableCt :: Ct -> Bool
isDroppableCt ct :: Ct
ct
  = CtEvidence -> Bool
isDerived CtEvidence
ev Bool -> Bool -> Bool
&& Bool -> Bool
not Bool
keep_deriv
    -- Drop only derived constraints, and then only if they
    -- obey Note [Dropping derived constraints]
  where
    ev :: CtEvidence
ev   = Ct -> CtEvidence
ctEvidence Ct
ct
    loc :: CtLoc
loc  = CtEvidence -> CtLoc
ctEvLoc CtEvidence
ev
    orig :: CtOrigin
orig = CtLoc -> CtOrigin
ctLocOrigin CtLoc
loc

    keep_deriv :: Bool
keep_deriv
      = case Ct
ct of
          CHoleCan {} -> Bool
True
          CIrredCan { cc_insol :: Ct -> Bool
cc_insol = Bool
insoluble }
                      -> Bool -> Bool
keep_eq Bool
insoluble
          _           -> Bool -> Bool
keep_eq Bool
False

    keep_eq :: Bool -> Bool
keep_eq definitely_insoluble :: Bool
definitely_insoluble
       | CtOrigin -> Bool
isGivenOrigin CtOrigin
orig    -- Arising only from givens
       = Bool
definitely_insoluble  -- Keep only definitely insoluble
       | Bool
otherwise
       = case CtOrigin
orig of
           KindEqOrigin {} -> Bool
True    -- See Note [Dropping derived constraints]

           -- See Note [Dropping derived constraints]
           -- For fundeps, drop wanted/wanted interactions
           FunDepOrigin2 {} -> Bool
True   -- Top-level/Wanted
           FunDepOrigin1 _ loc1 :: CtLoc
loc1 _ loc2 :: CtLoc
loc2
             | Bool
g1 Bool -> Bool -> Bool
|| Bool
g2  -> Bool
True  -- Given/Wanted errors: keep all
             | Bool
otherwise -> Bool
False -- Wanted/Wanted errors: discard
             where
               g1 :: Bool
g1 = CtLoc -> Bool
isGivenLoc CtLoc
loc1
               g2 :: Bool
g2 = CtLoc -> Bool
isGivenLoc CtLoc
loc2

           _ -> Bool
False

arisesFromGivens :: Ct -> Bool
arisesFromGivens :: Ct -> Bool
arisesFromGivens ct :: Ct
ct
  = case Ct -> CtEvidence
ctEvidence Ct
ct of
      CtGiven {}                   -> Bool
True
      CtWanted {}                  -> Bool
False
      CtDerived { ctev_loc :: CtEvidence -> CtLoc
ctev_loc = CtLoc
loc } -> CtLoc -> Bool
isGivenLoc CtLoc
loc

isGivenLoc :: CtLoc -> Bool
isGivenLoc :: CtLoc -> Bool
isGivenLoc loc :: CtLoc
loc = CtOrigin -> Bool
isGivenOrigin (CtLoc -> CtOrigin
ctLocOrigin CtLoc
loc)

isGivenOrigin :: CtOrigin -> Bool
isGivenOrigin :: CtOrigin -> Bool
isGivenOrigin (GivenOrigin {})          = Bool
True
isGivenOrigin (FunDepOrigin1 _ l1 :: CtLoc
l1 _ l2 :: CtLoc
l2) = CtLoc -> Bool
isGivenLoc CtLoc
l1 Bool -> Bool -> Bool
&& CtLoc -> Bool
isGivenLoc CtLoc
l2
isGivenOrigin (FunDepOrigin2 _ o1 :: CtOrigin
o1 _ _)  = CtOrigin -> Bool
isGivenOrigin CtOrigin
o1
isGivenOrigin _                         = Bool
False

{- Note [Dropping derived constraints]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
In general we discard derived constraints at the end of constraint solving;
see dropDerivedWC.  For example

 * Superclasses: if we have an unsolved [W] (Ord a), we don't want to
   complain about an unsolved [D] (Eq a) as well.

 * If we have [W] a ~ Int, [W] a ~ Bool, improvement will generate
   [D] Int ~ Bool, and we don't want to report that because it's
   incomprehensible. That is why we don't rewrite wanteds with wanteds!

 * We might float out some Wanteds from an implication, leaving behind
   their insoluble Deriveds. For example:

   forall a[2]. [W] alpha[1] ~ Int
                [W] alpha[1] ~ Bool
                [D] Int ~ Bool

   The Derived is insoluble, but we very much want to drop it when floating
   out.

But (tiresomely) we do keep *some* Derived constraints:

 * Type holes are derived constraints, because they have no evidence
   and we want to keep them, so we get the error report

 * Insoluble kind equalities (e.g. [D] * ~ (* -> *)), with
   KindEqOrigin, may arise from a type equality a ~ Int#, say.  See
   Note [Equalities with incompatible kinds] in TcCanonical.
   Keeping these around produces better error messages, in practice.
   E.g., test case dependent/should_fail/T11471

 * We keep most derived equalities arising from functional dependencies
      - Given/Given interactions (subset of FunDepOrigin1):
        The definitely-insoluble ones reflect unreachable code.

        Others not-definitely-insoluble ones like [D] a ~ Int do not
        reflect unreachable code; indeed if fundeps generated proofs, it'd
        be a useful equality.  See Trac #14763.   So we discard them.

      - Given/Wanted interacGiven or Wanted interacting with an
        instance declaration (FunDepOrigin2)

      - Given/Wanted interactions (FunDepOrigin1); see Trac #9612

      - But for Wanted/Wanted interactions we do /not/ want to report an
        error (Trac #13506).  Consider [W] C Int Int, [W] C Int Bool, with
        a fundep on class C.  We don't want to report an insoluble Int~Bool;
        c.f. "wanteds do not rewrite wanteds".

To distinguish these cases we use the CtOrigin.

NB: we keep *all* derived insolubles under some circumstances:

  * They are looked at by simplifyInfer, to decide whether to
    generalise.  Example: [W] a ~ Int, [W] a ~ Bool
    We get [D] Int ~ Bool, and indeed the constraints are insoluble,
    and we want simplifyInfer to see that, even though we don't
    ultimately want to generate an (inexplicable) error message from it


************************************************************************
*                                                                      *
                    CtEvidence
         The "flavor" of a canonical constraint
*                                                                      *
************************************************************************
-}

isWantedCt :: Ct -> Bool
isWantedCt :: Ct -> Bool
isWantedCt = CtEvidence -> Bool
isWanted (CtEvidence -> Bool) -> (Ct -> CtEvidence) -> Ct -> Bool
forall b c a. (b -> c) -> (a -> b) -> a -> c
. Ct -> CtEvidence
ctEvidence

isGivenCt :: Ct -> Bool
isGivenCt :: Ct -> Bool
isGivenCt = CtEvidence -> Bool
isGiven (CtEvidence -> Bool) -> (Ct -> CtEvidence) -> Ct -> Bool
forall b c a. (b -> c) -> (a -> b) -> a -> c
. Ct -> CtEvidence
ctEvidence

isDerivedCt :: Ct -> Bool
isDerivedCt :: Ct -> Bool
isDerivedCt = CtEvidence -> Bool
isDerived (CtEvidence -> Bool) -> (Ct -> CtEvidence) -> Ct -> Bool
forall b c a. (b -> c) -> (a -> b) -> a -> c
. Ct -> CtEvidence
ctEvidence

isCTyEqCan :: Ct -> Bool
isCTyEqCan :: Ct -> Bool
isCTyEqCan (CTyEqCan {})  = Bool
True
isCTyEqCan (CFunEqCan {}) = Bool
False
isCTyEqCan _              = Bool
False

isCDictCan_Maybe :: Ct -> Maybe Class
isCDictCan_Maybe :: Ct -> Maybe Class
isCDictCan_Maybe (CDictCan {cc_class :: Ct -> Class
cc_class = Class
cls })  = Class -> Maybe Class
forall a. a -> Maybe a
Just Class
cls
isCDictCan_Maybe _              = Maybe Class
forall a. Maybe a
Nothing

isCFunEqCan_maybe :: Ct -> Maybe (TyCon, [Type])
isCFunEqCan_maybe :: Ct -> Maybe (TyCon, [Type])
isCFunEqCan_maybe (CFunEqCan { cc_fun :: Ct -> TyCon
cc_fun = TyCon
tc, cc_tyargs :: Ct -> [Type]
cc_tyargs = [Type]
xis }) = (TyCon, [Type]) -> Maybe (TyCon, [Type])
forall a. a -> Maybe a
Just (TyCon
tc, [Type]
xis)
isCFunEqCan_maybe _ = Maybe (TyCon, [Type])
forall a. Maybe a
Nothing

isCFunEqCan :: Ct -> Bool
isCFunEqCan :: Ct -> Bool
isCFunEqCan (CFunEqCan {}) = Bool
True
isCFunEqCan _ = Bool
False

isCNonCanonical :: Ct -> Bool
isCNonCanonical :: Ct -> Bool
isCNonCanonical (CNonCanonical {}) = Bool
True
isCNonCanonical _ = Bool
False

isHoleCt:: Ct -> Bool
isHoleCt :: Ct -> Bool
isHoleCt (CHoleCan {}) = Bool
True
isHoleCt _ = Bool
False

isOutOfScopeCt :: Ct -> Bool
-- We treat expression holes representing out-of-scope variables a bit
-- differently when it comes to error reporting
isOutOfScopeCt :: Ct -> Bool
isOutOfScopeCt (CHoleCan { cc_hole :: Ct -> Hole
cc_hole = ExprHole (OutOfScope {}) }) = Bool
True
isOutOfScopeCt _ = Bool
False

isExprHoleCt :: Ct -> Bool
isExprHoleCt :: Ct -> Bool
isExprHoleCt (CHoleCan { cc_hole :: Ct -> Hole
cc_hole = ExprHole {} }) = Bool
True
isExprHoleCt _ = Bool
False

isTypeHoleCt :: Ct -> Bool
isTypeHoleCt :: Ct -> Bool
isTypeHoleCt (CHoleCan { cc_hole :: Ct -> Hole
cc_hole = TypeHole {} }) = Bool
True
isTypeHoleCt _ = Bool
False


{- Note [Custom type errors in constraints]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

When GHC reports a type-error about an unsolved-constraint, we check
to see if the constraint contains any custom-type errors, and if so
we report them.  Here are some examples of constraints containing type
errors:

TypeError msg           -- The actual constraint is a type error

TypError msg ~ Int      -- Some type was supposed to be Int, but ended up
                        -- being a type error instead

Eq (TypeError msg)      -- A class constraint is stuck due to a type error

F (TypeError msg) ~ a   -- A type function failed to evaluate due to a type err

It is also possible to have constraints where the type error is nested deeper,
for example see #11990, and also:

Eq (F (TypeError msg))  -- Here the type error is nested under a type-function
                        -- call, which failed to evaluate because of it,
                        -- and so the `Eq` constraint was unsolved.
                        -- This may happen when one function calls another
                        -- and the called function produced a custom type error.
-}

-- | A constraint is considered to be a custom type error, if it contains
-- custom type errors anywhere in it.
-- See Note [Custom type errors in constraints]
getUserTypeErrorMsg :: Ct -> Maybe Type
getUserTypeErrorMsg :: Ct -> Maybe Type
getUserTypeErrorMsg ct :: Ct
ct = Type -> Maybe Type
findUserTypeError (Ct -> Type
ctPred Ct
ct)
  where
  findUserTypeError :: Type -> Maybe Type
findUserTypeError t :: Type
t = [Maybe Type] -> Maybe Type
forall (t :: * -> *) (m :: * -> *) a.
(Foldable t, MonadPlus m) =>
t (m a) -> m a
msum ( Type -> Maybe Type
userTypeError_maybe Type
t
                             Maybe Type -> [Maybe Type] -> [Maybe Type]
forall a. a -> [a] -> [a]
: (Type -> Maybe Type) -> [Type] -> [Maybe Type]
forall a b. (a -> b) -> [a] -> [b]
map Type -> Maybe Type
findUserTypeError (Type -> [Type]
subTys Type
t)
                             )

  subTys :: Type -> [Type]
subTys t :: Type
t            = case Type -> (Type, [Type])
splitAppTys Type
t of
                          (t :: Type
t,[]) ->
                            case HasDebugCallStack => Type -> Maybe (TyCon, [Type])
Type -> Maybe (TyCon, [Type])
splitTyConApp_maybe Type
t of
                              Nothing     -> []
                              Just (_,ts :: [Type]
ts) -> [Type]
ts
                          (t :: Type
t,ts :: [Type]
ts) -> Type
t Type -> [Type] -> [Type]
forall a. a -> [a] -> [a]
: [Type]
ts




isUserTypeErrorCt :: Ct -> Bool
isUserTypeErrorCt :: Ct -> Bool
isUserTypeErrorCt ct :: Ct
ct = case Ct -> Maybe Type
getUserTypeErrorMsg Ct
ct of
                         Just _ -> Bool
True
                         _      -> Bool
False

isPendingScDict :: Ct -> Maybe Ct
-- Says whether this is a CDictCan with cc_pend_sc is True,
-- AND if so flips the flag
isPendingScDict :: Ct -> Maybe Ct
isPendingScDict ct :: Ct
ct@(CDictCan { cc_pend_sc :: Ct -> Bool
cc_pend_sc = Bool
True })
                  = Ct -> Maybe Ct
forall a. a -> Maybe a
Just (Ct
ct { cc_pend_sc :: Bool
cc_pend_sc = Bool
False })
isPendingScDict _ = Maybe Ct
forall a. Maybe a
Nothing

isPendingScInst :: QCInst -> Maybe QCInst
-- Same as isPrendinScDict, but for QCInsts
isPendingScInst :: QCInst -> Maybe QCInst
isPendingScInst qci :: QCInst
qci@(QCI { qci_pend_sc :: QCInst -> Bool
qci_pend_sc = Bool
True })
                  = QCInst -> Maybe QCInst
forall a. a -> Maybe a
Just (QCInst
qci { qci_pend_sc :: Bool
qci_pend_sc = Bool
False })
isPendingScInst _ = Maybe QCInst
forall a. Maybe a
Nothing

setPendingScDict :: Ct -> Ct
-- Set the cc_pend_sc flag to True
setPendingScDict :: Ct -> Ct
setPendingScDict ct :: Ct
ct@(CDictCan { cc_pend_sc :: Ct -> Bool
cc_pend_sc = Bool
False })
                    = Ct
ct { cc_pend_sc :: Bool
cc_pend_sc = Bool
True }
setPendingScDict ct :: Ct
ct = Ct
ct

superClassesMightHelp :: WantedConstraints -> Bool
-- ^ True if taking superclasses of givens, or of wanteds (to perhaps
-- expose more equalities or functional dependencies) might help to
-- solve this constraint.  See Note [When superclasses help]
superClassesMightHelp :: WantedConstraints -> Bool
superClassesMightHelp (WC { wc_simple :: WantedConstraints -> Cts
wc_simple = Cts
simples, wc_impl :: WantedConstraints -> Bag Implication
wc_impl = Bag Implication
implics })
  = (Ct -> Bool) -> Cts -> Bool
forall a. (a -> Bool) -> Bag a -> Bool
anyBag Ct -> Bool
might_help_ct Cts
simples Bool -> Bool -> Bool
|| (Implication -> Bool) -> Bag Implication -> Bool
forall a. (a -> Bool) -> Bag a -> Bool
anyBag Implication -> Bool
might_help_implic Bag Implication
implics
  where
    might_help_implic :: Implication -> Bool
might_help_implic ic :: Implication
ic
       | ImplicStatus
IC_Unsolved <- Implication -> ImplicStatus
ic_status Implication
ic = WantedConstraints -> Bool
superClassesMightHelp (Implication -> WantedConstraints
ic_wanted Implication
ic)
       | Bool
otherwise                   = Bool
False

    might_help_ct :: Ct -> Bool
might_help_ct ct :: Ct
ct = Ct -> Bool
isWantedCt Ct
ct Bool -> Bool -> Bool
&& Bool -> Bool
not (Ct -> Bool
is_ip Ct
ct)

    is_ip :: Ct -> Bool
is_ip (CDictCan { cc_class :: Ct -> Class
cc_class = Class
cls }) = Class -> Bool
isIPClass Class
cls
    is_ip _                             = Bool
False

getPendingWantedScs :: Cts -> ([Ct], Cts)
getPendingWantedScs :: Cts -> ([Ct], Cts)
getPendingWantedScs simples :: Cts
simples
  = ([Ct] -> Ct -> ([Ct], Ct)) -> [Ct] -> Cts -> ([Ct], Cts)
forall acc x y.
(acc -> x -> (acc, y)) -> acc -> Bag x -> (acc, Bag y)
mapAccumBagL [Ct] -> Ct -> ([Ct], Ct)
get [] Cts
simples
  where
    get :: [Ct] -> Ct -> ([Ct], Ct)
get acc :: [Ct]
acc ct :: Ct
ct | Just ct' :: Ct
ct' <- Ct -> Maybe Ct
isPendingScDict Ct
ct
               = (Ct
ct'Ct -> [Ct] -> [Ct]
forall a. a -> [a] -> [a]
:[Ct]
acc, Ct
ct')
               | Bool
otherwise
               = ([Ct]
acc,     Ct
ct)

{- Note [When superclasses help]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
First read Note [The superclass story] in TcCanonical.

We expand superclasses and iterate only if there is at unsolved wanted
for which expansion of superclasses (e.g. from given constraints)
might actually help. The function superClassesMightHelp tells if
doing this superclass expansion might help solve this constraint.
Note that

  * We look inside implications; maybe it'll help to expand the Givens
    at level 2 to help solve an unsolved Wanted buried inside an
    implication.  E.g.
        forall a. Ord a => forall b. [W] Eq a

  * Superclasses help only for Wanted constraints.  Derived constraints
    are not really "unsolved" and we certainly don't want them to
    trigger superclass expansion. This was a good part of the loop
    in  Trac #11523

  * Even for Wanted constraints, we say "no" for implicit parameters.
    we have [W] ?x::ty, expanding superclasses won't help:
      - Superclasses can't be implicit parameters
      - If we have a [G] ?x:ty2, then we'll have another unsolved
        [D] ty ~ ty2 (from the functional dependency)
        which will trigger superclass expansion.

    It's a bit of a special case, but it's easy to do.  The runtime cost
    is low because the unsolved set is usually empty anyway (errors
    aside), and the first non-imlicit-parameter will terminate the search.

    The special case is worth it (Trac #11480, comment:2) because it
    applies to CallStack constraints, which aren't type errors. If we have
       f :: (C a) => blah
       f x = ...undefined...
    we'll get a CallStack constraint.  If that's the only unsolved
    constraint it'll eventually be solved by defaulting.  So we don't
    want to emit warnings about hitting the simplifier's iteration
    limit.  A CallStack constraint really isn't an unsolved
    constraint; it can always be solved by defaulting.
-}

singleCt :: Ct -> Cts
singleCt :: Ct -> Cts
singleCt = Ct -> Cts
forall a. a -> Bag a
unitBag

andCts :: Cts -> Cts -> Cts
andCts :: Cts -> Cts -> Cts
andCts = Cts -> Cts -> Cts
forall a. Bag a -> Bag a -> Bag a
unionBags

listToCts :: [Ct] -> Cts
listToCts :: [Ct] -> Cts
listToCts = [Ct] -> Cts
forall a. [a] -> Bag a
listToBag

ctsElts :: Cts -> [Ct]
ctsElts :: Cts -> [Ct]
ctsElts = Cts -> [Ct]
forall a. Bag a -> [a]
bagToList

consCts :: Ct -> Cts -> Cts
consCts :: Ct -> Cts -> Cts
consCts = Ct -> Cts -> Cts
forall a. a -> Bag a -> Bag a
consBag

snocCts :: Cts -> Ct -> Cts
snocCts :: Cts -> Ct -> Cts
snocCts = Cts -> Ct -> Cts
forall a. Bag a -> a -> Bag a
snocBag

extendCtsList :: Cts -> [Ct] -> Cts
extendCtsList :: Cts -> [Ct] -> Cts
extendCtsList cts :: Cts
cts xs :: [Ct]
xs | [Ct] -> Bool
forall (t :: * -> *) a. Foldable t => t a -> Bool
null [Ct]
xs   = Cts
cts
                     | Bool
otherwise = Cts
cts Cts -> Cts -> Cts
forall a. Bag a -> Bag a -> Bag a
`unionBags` [Ct] -> Cts
forall a. [a] -> Bag a
listToBag [Ct]
xs

andManyCts :: [Cts] -> Cts
andManyCts :: [Cts] -> Cts
andManyCts = [Cts] -> Cts
forall a. [Bag a] -> Bag a
unionManyBags

emptyCts :: Cts
emptyCts :: Cts
emptyCts = Cts
forall a. Bag a
emptyBag

isEmptyCts :: Cts -> Bool
isEmptyCts :: Cts -> Bool
isEmptyCts = Cts -> Bool
forall a. Bag a -> Bool
isEmptyBag

pprCts :: Cts -> SDoc
pprCts :: Cts -> SDoc
pprCts cts :: Cts
cts = [SDoc] -> SDoc
vcat ((Ct -> SDoc) -> [Ct] -> [SDoc]
forall a b. (a -> b) -> [a] -> [b]
map Ct -> SDoc
forall a. Outputable a => a -> SDoc
ppr (Cts -> [Ct]
forall a. Bag a -> [a]
bagToList Cts
cts))

{-
************************************************************************
*                                                                      *
                Wanted constraints
     These are forced to be in TcRnTypes because
           TcLclEnv mentions WantedConstraints
           WantedConstraint mentions CtLoc
           CtLoc mentions ErrCtxt
           ErrCtxt mentions TcM
*                                                                      *
v%************************************************************************
-}

data WantedConstraints
  = WC { WantedConstraints -> Cts
wc_simple :: Cts              -- Unsolved constraints, all wanted
       , WantedConstraints -> Bag Implication
wc_impl   :: Bag Implication
    }

emptyWC :: WantedConstraints
emptyWC :: WantedConstraints
emptyWC = WC :: Cts -> Bag Implication -> WantedConstraints
WC { wc_simple :: Cts
wc_simple = Cts
forall a. Bag a
emptyBag, wc_impl :: Bag Implication
wc_impl = Bag Implication
forall a. Bag a
emptyBag }

mkSimpleWC :: [CtEvidence] -> WantedConstraints
mkSimpleWC :: [CtEvidence] -> WantedConstraints
mkSimpleWC cts :: [CtEvidence]
cts
  = WC :: Cts -> Bag Implication -> WantedConstraints
WC { wc_simple :: Cts
wc_simple = [Ct] -> Cts
forall a. [a] -> Bag a
listToBag ((CtEvidence -> Ct) -> [CtEvidence] -> [Ct]
forall a b. (a -> b) -> [a] -> [b]
map CtEvidence -> Ct
mkNonCanonical [CtEvidence]
cts)
       , wc_impl :: Bag Implication
wc_impl = Bag Implication
forall a. Bag a
emptyBag }

mkImplicWC :: Bag Implication -> WantedConstraints
mkImplicWC :: Bag Implication -> WantedConstraints
mkImplicWC implic :: Bag Implication
implic
  = WC :: Cts -> Bag Implication -> WantedConstraints
WC { wc_simple :: Cts
wc_simple = Cts
forall a. Bag a
emptyBag, wc_impl :: Bag Implication
wc_impl = Bag Implication
implic }

isEmptyWC :: WantedConstraints -> Bool
isEmptyWC :: WantedConstraints -> Bool
isEmptyWC (WC { wc_simple :: WantedConstraints -> Cts
wc_simple = Cts
f, wc_impl :: WantedConstraints -> Bag Implication
wc_impl = Bag Implication
i })
  = Cts -> Bool
forall a. Bag a -> Bool
isEmptyBag Cts
f Bool -> Bool -> Bool
&& Bag Implication -> Bool
forall a. Bag a -> Bool
isEmptyBag Bag Implication
i


-- | Checks whether a the given wanted constraints are solved, i.e.
-- that there are no simple constraints left and all the implications
-- are solved.
isSolvedWC :: WantedConstraints -> Bool
isSolvedWC :: WantedConstraints -> Bool
isSolvedWC WC {wc_simple :: WantedConstraints -> Cts
wc_simple = Cts
wc_simple, wc_impl :: WantedConstraints -> Bag Implication
wc_impl = Bag Implication
wc_impl} =
  Cts -> Bool
forall a. Bag a -> Bool
isEmptyBag Cts
wc_simple Bool -> Bool -> Bool
&& (Implication -> Bool) -> Bag Implication -> Bool
forall a. (a -> Bool) -> Bag a -> Bool
allBag (ImplicStatus -> Bool
isSolvedStatus (ImplicStatus -> Bool)
-> (Implication -> ImplicStatus) -> Implication -> Bool
forall b c a. (b -> c) -> (a -> b) -> a -> c
. Implication -> ImplicStatus
ic_status) Bag Implication
wc_impl

andWC :: WantedConstraints -> WantedConstraints -> WantedConstraints
andWC :: WantedConstraints -> WantedConstraints -> WantedConstraints
andWC (WC { wc_simple :: WantedConstraints -> Cts
wc_simple = Cts
f1, wc_impl :: WantedConstraints -> Bag Implication
wc_impl = Bag Implication
i1 })
      (WC { wc_simple :: WantedConstraints -> Cts
wc_simple = Cts
f2, wc_impl :: WantedConstraints -> Bag Implication
wc_impl = Bag Implication
i2 })
  = WC :: Cts -> Bag Implication -> WantedConstraints
WC { wc_simple :: Cts
wc_simple = Cts
f1 Cts -> Cts -> Cts
forall a. Bag a -> Bag a -> Bag a
`unionBags` Cts
f2
       , wc_impl :: Bag Implication
wc_impl   = Bag Implication
i1 Bag Implication -> Bag Implication -> Bag Implication
forall a. Bag a -> Bag a -> Bag a
`unionBags` Bag Implication
i2 }

unionsWC :: [WantedConstraints] -> WantedConstraints
unionsWC :: [WantedConstraints] -> WantedConstraints
unionsWC = (WantedConstraints -> WantedConstraints -> WantedConstraints)
-> WantedConstraints -> [WantedConstraints] -> WantedConstraints
forall (t :: * -> *) a b.
Foldable t =>
(a -> b -> b) -> b -> t a -> b
foldr WantedConstraints -> WantedConstraints -> WantedConstraints
andWC WantedConstraints
emptyWC

addSimples :: WantedConstraints -> Bag Ct -> WantedConstraints
addSimples :: WantedConstraints -> Cts -> WantedConstraints
addSimples wc :: WantedConstraints
wc cts :: Cts
cts
  = WantedConstraints
wc { wc_simple :: Cts
wc_simple = WantedConstraints -> Cts
wc_simple WantedConstraints
wc Cts -> Cts -> Cts
forall a. Bag a -> Bag a -> Bag a
`unionBags` Cts
cts }
    -- Consider: Put the new constraints at the front, so they get solved first

addImplics :: WantedConstraints -> Bag Implication -> WantedConstraints
addImplics :: WantedConstraints -> Bag Implication -> WantedConstraints
addImplics wc :: WantedConstraints
wc implic :: Bag Implication
implic = WantedConstraints
wc { wc_impl :: Bag Implication
wc_impl = WantedConstraints -> Bag Implication
wc_impl WantedConstraints
wc Bag Implication -> Bag Implication -> Bag Implication
forall a. Bag a -> Bag a -> Bag a
`unionBags` Bag Implication
implic }

addInsols :: WantedConstraints -> Bag Ct -> WantedConstraints
addInsols :: WantedConstraints -> Cts -> WantedConstraints
addInsols wc :: WantedConstraints
wc cts :: Cts
cts
  = WantedConstraints
wc { wc_simple :: Cts
wc_simple = WantedConstraints -> Cts
wc_simple WantedConstraints
wc Cts -> Cts -> Cts
forall a. Bag a -> Bag a -> Bag a
`unionBags` Cts
cts }

insolublesOnly :: WantedConstraints -> WantedConstraints
-- Keep only the definitely-insoluble constraints
insolublesOnly :: WantedConstraints -> WantedConstraints
insolublesOnly (WC { wc_simple :: WantedConstraints -> Cts
wc_simple = Cts
simples, wc_impl :: WantedConstraints -> Bag Implication
wc_impl = Bag Implication
implics })
  = WC :: Cts -> Bag Implication -> WantedConstraints
WC { wc_simple :: Cts
wc_simple = (Ct -> Bool) -> Cts -> Cts
forall a. (a -> Bool) -> Bag a -> Bag a
filterBag Ct -> Bool
insolubleCt Cts
simples
       , wc_impl :: Bag Implication
wc_impl   = (Implication -> Implication) -> Bag Implication -> Bag Implication
forall a b. (a -> b) -> Bag a -> Bag b
mapBag Implication -> Implication
implic_insols_only Bag Implication
implics }
  where
    implic_insols_only :: Implication -> Implication
implic_insols_only implic :: Implication
implic
      = Implication
implic { ic_wanted :: WantedConstraints
ic_wanted = WantedConstraints -> WantedConstraints
insolublesOnly (Implication -> WantedConstraints
ic_wanted Implication
implic) }

isSolvedStatus :: ImplicStatus -> Bool
isSolvedStatus :: ImplicStatus -> Bool
isSolvedStatus (IC_Solved {}) = Bool
True
isSolvedStatus _              = Bool
False

isInsolubleStatus :: ImplicStatus -> Bool
isInsolubleStatus :: ImplicStatus -> Bool
isInsolubleStatus IC_Insoluble    = Bool
True
isInsolubleStatus IC_BadTelescope = Bool
True
isInsolubleStatus _               = Bool
False

insolubleImplic :: Implication -> Bool
insolubleImplic :: Implication -> Bool
insolubleImplic ic :: Implication
ic = ImplicStatus -> Bool
isInsolubleStatus (Implication -> ImplicStatus
ic_status Implication
ic)

insolubleWC :: WantedConstraints -> Bool
insolubleWC :: WantedConstraints -> Bool
insolubleWC (WC { wc_impl :: WantedConstraints -> Bag Implication
wc_impl = Bag Implication
implics, wc_simple :: WantedConstraints -> Cts
wc_simple = Cts
simples })
  =  (Ct -> Bool) -> Cts -> Bool
forall a. (a -> Bool) -> Bag a -> Bool
anyBag Ct -> Bool
insolubleCt Cts
simples
  Bool -> Bool -> Bool
|| (Implication -> Bool) -> Bag Implication -> Bool
forall a. (a -> Bool) -> Bag a -> Bool
anyBag Implication -> Bool
insolubleImplic Bag Implication
implics

insolubleCt :: Ct -> Bool
-- Definitely insoluble, in particular /excluding/ type-hole constraints
-- Namely: a) an equality constraint
--         b) that is insoluble
--         c) and does not arise from a Given
insolubleCt :: Ct -> Bool
insolubleCt ct :: Ct
ct
  | Ct -> Bool
isHoleCt Ct
ct            = Ct -> Bool
isOutOfScopeCt Ct
ct  -- See Note [Insoluble holes]
  | Bool -> Bool
not (Ct -> Bool
insolubleEqCt Ct
ct) = Bool
False
  | Ct -> Bool
arisesFromGivens Ct
ct    = Bool
False              -- See Note [Given insolubles]
  | Bool
otherwise              = Bool
True

insolubleEqCt :: Ct -> Bool
-- Returns True of /equality/ constraints
-- that are /definitely/ insoluble
-- It won't detect some definite errors like
--       F a ~ T (F a)
-- where F is a type family, which actually has an occurs check
--
-- The function is tuned for application /after/ constraint solving
--       i.e. assuming canonicalisation has been done
-- E.g.  It'll reply True  for     a ~ [a]
--               but False for   [a] ~ a
-- and
--                   True for  Int ~ F a Int
--               but False for  Maybe Int ~ F a Int Int
--               (where F is an arity-1 type function)
insolubleEqCt :: Ct -> Bool
insolubleEqCt (CIrredCan { cc_insol :: Ct -> Bool
cc_insol = Bool
insol }) = Bool
insol
insolubleEqCt _                                = Bool
False

instance Outputable WantedConstraints where
  ppr :: WantedConstraints -> SDoc
ppr (WC {wc_simple :: WantedConstraints -> Cts
wc_simple = Cts
s, wc_impl :: WantedConstraints -> Bag Implication
wc_impl = Bag Implication
i})
   = FilePath -> SDoc
text "WC" SDoc -> SDoc -> SDoc
<+> SDoc -> SDoc
braces ([SDoc] -> SDoc
vcat
        [ SDoc -> Cts -> SDoc
forall a. Outputable a => SDoc -> Bag a -> SDoc
ppr_bag (FilePath -> SDoc
text "wc_simple") Cts
s
        , SDoc -> Bag Implication -> SDoc
forall a. Outputable a => SDoc -> Bag a -> SDoc
ppr_bag (FilePath -> SDoc
text "wc_impl") Bag Implication
i ])

ppr_bag :: Outputable a => SDoc -> Bag a -> SDoc
ppr_bag :: SDoc -> Bag a -> SDoc
ppr_bag doc :: SDoc
doc bag :: Bag a
bag
 | Bag a -> Bool
forall a. Bag a -> Bool
isEmptyBag Bag a
bag = SDoc
empty
 | Bool
otherwise      = SDoc -> Int -> SDoc -> SDoc
hang (SDoc
doc SDoc -> SDoc -> SDoc
<+> SDoc
equals)
                       2 ((a -> SDoc -> SDoc) -> SDoc -> Bag a -> SDoc
forall a r. (a -> r -> r) -> r -> Bag a -> r
foldrBag (SDoc -> SDoc -> SDoc
($$) (SDoc -> SDoc -> SDoc) -> (a -> SDoc) -> a -> SDoc -> SDoc
forall b c a. (b -> c) -> (a -> b) -> a -> c
. a -> SDoc
forall a. Outputable a => a -> SDoc
ppr) SDoc
empty Bag a
bag)

{- Note [Given insolubles]
~~~~~~~~~~~~~~~~~~~~~~~~~~
Consider (Trac #14325, comment:)
    class (a~b) => C a b

    foo :: C a c => a -> c
    foo x = x

    hm3 :: C (f b) b => b -> f b
    hm3 x = foo x

In the RHS of hm3, from the [G] C (f b) b we get the insoluble
[G] f b ~# b.  Then we also get an unsolved [W] C b (f b).
Residual implication looks like
    forall b. C (f b) b => [G] f b ~# b
                           [W] C f (f b)

We do /not/ want to set the implication status to IC_Insoluble,
because that'll suppress reports of [W] C b (f b).  But we
may not report the insoluble [G] f b ~# b either (see Note [Given errors]
in TcErrors), so we may fail to report anything at all!  Yikes.

The same applies to Derived constraints that /arise from/ Givens.
E.g.   f :: (C Int [a]) => blah
where a fundep means we get
       [D] Int ~ [a]
By the same reasoning we must not suppress other errors (Trac #15767)

Bottom line: insolubleWC (called in TcSimplify.setImplicationStatus)
             should ignore givens even if they are insoluble.

Note [Insoluble holes]
~~~~~~~~~~~~~~~~~~~~~~
Hole constraints that ARE NOT treated as truly insoluble:
  a) type holes, arising from PartialTypeSignatures,
  b) "true" expression holes arising from TypedHoles

An "expression hole" or "type hole" constraint isn't really an error
at all; it's a report saying "_ :: Int" here.  But an out-of-scope
variable masquerading as expression holes IS treated as truly
insoluble, so that it trumps other errors during error reporting.
Yuk!

************************************************************************
*                                                                      *
                Implication constraints
*                                                                      *
************************************************************************
-}

data Implication
  = Implic {   -- Invariants for a tree of implications:
               -- see TcType Note [TcLevel and untouchable type variables]

      Implication -> TcLevel
ic_tclvl :: TcLevel,       -- TcLevel of unification variables
                                 -- allocated /inside/ this implication

      Implication -> [TyVar]
ic_skols :: [TcTyVar],     -- Introduced skolems
      Implication -> SkolemInfo
ic_info  :: SkolemInfo,    -- See Note [Skolems in an implication]
                                 -- See Note [Shadowing in a constraint]
      Implication -> Maybe SDoc
ic_telescope :: Maybe SDoc,  -- User-written telescope, if there is one
                                   -- The list of skolems is order-checked
                                   -- if and only if this is a Just.
                                   -- See Note [Keeping scoped variables in order: Explicit]
                                   -- in TcHsType

      Implication -> [TyVar]
ic_given  :: [EvVar],      -- Given evidence variables
                                 --   (order does not matter)
                                 -- See Invariant (GivenInv) in TcType

      Implication -> Bool
ic_no_eqs :: Bool,         -- True  <=> ic_givens have no equalities, for sure
                                 -- False <=> ic_givens might have equalities

      Implication -> Env TcGblEnv TcLclEnv
ic_env   :: Env TcGblEnv TcLclEnv,
                                 -- Records the Env at the time of creation.
                                 --
                                 -- This is primarly needed for the enclosed
                                 -- TcLclEnv, which gives the source location
                                 -- and error context for the implication, and
                                 -- hence for all the given evidence variables.
                                 --
                                 -- The enclosed DynFlags also influences error
                                 -- reporting. See Note [Avoid
                                 -- -Winaccessible-code when deriving] in
                                 -- TcInstDcls.

      Implication -> WantedConstraints
ic_wanted :: WantedConstraints,  -- The wanteds
                                       -- See Invariang (WantedInf) in TcType

      Implication -> EvBindsVar
ic_binds  :: EvBindsVar,    -- Points to the place to fill in the
                                  -- abstraction and bindings.

      -- The ic_need fields keep track of which Given evidence
      -- is used by this implication or its children
      -- NB: including stuff used by nested implications that have since
      --     been discarded
      Implication -> TcTyVarSet
ic_need_inner :: VarSet,    -- Includes all used Given evidence
      Implication -> TcTyVarSet
ic_need_outer :: VarSet,    -- Includes only the free Given evidence
                                  --  i.e. ic_need_inner after deleting
                                  --       (a) givens (b) binders of ic_binds

      Implication -> ImplicStatus
ic_status   :: ImplicStatus
    }

-- | Create a new 'Implication' with as many sensible defaults for its fields
-- as possible. Note that the 'ic_tclvl', 'ic_binds', and 'ic_info' fields do
-- /not/ have sensible defaults, so they are initialized with lazy thunks that
-- will 'panic' if forced, so one should take care to initialize these fields
-- after creation.
--
-- This is monadic purely to look up the 'Env', which is used to initialize
-- 'ic_env'.
newImplication :: TcM Implication
newImplication :: TcM Implication
newImplication
  = do Env TcGblEnv TcLclEnv
env <- IOEnv (Env TcGblEnv TcLclEnv) (Env TcGblEnv TcLclEnv)
forall env. IOEnv env env
getEnv
       Implication -> TcM Implication
forall (m :: * -> *) a. Monad m => a -> m a
return (Implication
implicationPrototype { ic_env :: Env TcGblEnv TcLclEnv
ic_env = Env TcGblEnv TcLclEnv
env })

implicationPrototype :: Implication
implicationPrototype :: Implication
implicationPrototype
   = Implic :: TcLevel
-> [TyVar]
-> SkolemInfo
-> Maybe SDoc
-> [TyVar]
-> Bool
-> Env TcGblEnv TcLclEnv
-> WantedConstraints
-> EvBindsVar
-> TcTyVarSet
-> TcTyVarSet
-> ImplicStatus
-> Implication
Implic { -- These fields must be initialised
              ic_tclvl :: TcLevel
ic_tclvl      = FilePath -> TcLevel
forall a. FilePath -> a
panic "newImplic:tclvl"
            , ic_binds :: EvBindsVar
ic_binds      = FilePath -> EvBindsVar
forall a. FilePath -> a
panic "newImplic:binds"
            , ic_info :: SkolemInfo
ic_info       = FilePath -> SkolemInfo
forall a. FilePath -> a
panic "newImplic:info"
            , ic_env :: Env TcGblEnv TcLclEnv
ic_env        = FilePath -> Env TcGblEnv TcLclEnv
forall a. FilePath -> a
panic "newImplic:env"

              -- The rest have sensible default values
            , ic_skols :: [TyVar]
ic_skols      = []
            , ic_telescope :: Maybe SDoc
ic_telescope  = Maybe SDoc
forall a. Maybe a
Nothing
            , ic_given :: [TyVar]
ic_given      = []
            , ic_wanted :: WantedConstraints
ic_wanted     = WantedConstraints
emptyWC
            , ic_no_eqs :: Bool
ic_no_eqs     = Bool
False
            , ic_status :: ImplicStatus
ic_status     = ImplicStatus
IC_Unsolved
            , ic_need_inner :: TcTyVarSet
ic_need_inner = TcTyVarSet
emptyVarSet
            , ic_need_outer :: TcTyVarSet
ic_need_outer = TcTyVarSet
emptyVarSet }

-- | Retrieve the enclosed 'TcLclEnv' from an 'Implication'.
implicLclEnv :: Implication -> TcLclEnv
implicLclEnv :: Implication -> TcLclEnv
implicLclEnv = Env TcGblEnv TcLclEnv -> TcLclEnv
forall gbl lcl. Env gbl lcl -> lcl
env_lcl (Env TcGblEnv TcLclEnv -> TcLclEnv)
-> (Implication -> Env TcGblEnv TcLclEnv)
-> Implication
-> TcLclEnv
forall b c a. (b -> c) -> (a -> b) -> a -> c
. Implication -> Env TcGblEnv TcLclEnv
ic_env

-- | Retrieve the enclosed 'DynFlags' from an 'Implication'.
implicDynFlags :: Implication -> DynFlags
implicDynFlags :: Implication -> DynFlags
implicDynFlags = HscEnv -> DynFlags
hsc_dflags (HscEnv -> DynFlags)
-> (Implication -> HscEnv) -> Implication -> DynFlags
forall b c a. (b -> c) -> (a -> b) -> a -> c
. Env TcGblEnv TcLclEnv -> HscEnv
forall gbl lcl. Env gbl lcl -> HscEnv
env_top (Env TcGblEnv TcLclEnv -> HscEnv)
-> (Implication -> Env TcGblEnv TcLclEnv) -> Implication -> HscEnv
forall b c a. (b -> c) -> (a -> b) -> a -> c
. Implication -> Env TcGblEnv TcLclEnv
ic_env

data ImplicStatus
  = IC_Solved     -- All wanteds in the tree are solved, all the way down
       { ImplicStatus -> [TyVar]
ics_dead :: [EvVar] }  -- Subset of ic_given that are not needed
         -- See Note [Tracking redundant constraints] in TcSimplify

  | IC_Insoluble  -- At least one insoluble constraint in the tree

  | IC_BadTelescope  -- solved, but the skolems in the telescope are out of
                     -- dependency order

  | IC_Unsolved   -- Neither of the above; might go either way

instance Outputable Implication where
  ppr :: Implication -> SDoc
ppr (Implic { ic_tclvl :: Implication -> TcLevel
ic_tclvl = TcLevel
tclvl, ic_skols :: Implication -> [TyVar]
ic_skols = [TyVar]
skols
              , ic_given :: Implication -> [TyVar]
ic_given = [TyVar]
given, ic_no_eqs :: Implication -> Bool
ic_no_eqs = Bool
no_eqs
              , ic_wanted :: Implication -> WantedConstraints
ic_wanted = WantedConstraints
wanted, ic_status :: Implication -> ImplicStatus
ic_status = ImplicStatus
status
              , ic_binds :: Implication -> EvBindsVar
ic_binds = EvBindsVar
binds
              , ic_need_inner :: Implication -> TcTyVarSet
ic_need_inner = TcTyVarSet
need_in, ic_need_outer :: Implication -> TcTyVarSet
ic_need_outer = TcTyVarSet
need_out
              , ic_info :: Implication -> SkolemInfo
ic_info = SkolemInfo
info })
   = SDoc -> Int -> SDoc -> SDoc
hang (FilePath -> SDoc
text "Implic" SDoc -> SDoc -> SDoc
<+> SDoc
lbrace)
        2 ([SDoc] -> SDoc
sep [ FilePath -> SDoc
text "TcLevel =" SDoc -> SDoc -> SDoc
<+> TcLevel -> SDoc
forall a. Outputable a => a -> SDoc
ppr TcLevel
tclvl
               , FilePath -> SDoc
text "Skolems =" SDoc -> SDoc -> SDoc
<+> [TyVar] -> SDoc
pprTyVars [TyVar]
skols
               , FilePath -> SDoc
text "No-eqs =" SDoc -> SDoc -> SDoc
<+> Bool -> SDoc
forall a. Outputable a => a -> SDoc
ppr Bool
no_eqs
               , FilePath -> SDoc
text "Status =" SDoc -> SDoc -> SDoc
<+> ImplicStatus -> SDoc
forall a. Outputable a => a -> SDoc
ppr ImplicStatus
status
               , SDoc -> Int -> SDoc -> SDoc
hang (FilePath -> SDoc
text "Given =")  2 ([TyVar] -> SDoc
pprEvVars [TyVar]
given)
               , SDoc -> Int -> SDoc -> SDoc
hang (FilePath -> SDoc
text "Wanted =") 2 (WantedConstraints -> SDoc
forall a. Outputable a => a -> SDoc
ppr WantedConstraints
wanted)
               , FilePath -> SDoc
text "Binds =" SDoc -> SDoc -> SDoc
<+> EvBindsVar -> SDoc
forall a. Outputable a => a -> SDoc
ppr EvBindsVar
binds
               , SDoc -> SDoc
whenPprDebug (FilePath -> SDoc
text "Needed inner =" SDoc -> SDoc -> SDoc
<+> TcTyVarSet -> SDoc
forall a. Outputable a => a -> SDoc
ppr TcTyVarSet
need_in)
               , SDoc -> SDoc
whenPprDebug (FilePath -> SDoc
text "Needed outer =" SDoc -> SDoc -> SDoc
<+> TcTyVarSet -> SDoc
forall a. Outputable a => a -> SDoc
ppr TcTyVarSet
need_out)
               , SkolemInfo -> SDoc
pprSkolInfo SkolemInfo
info ] SDoc -> SDoc -> SDoc
<+> SDoc
rbrace)

instance Outputable ImplicStatus where
  ppr :: ImplicStatus -> SDoc
ppr IC_Insoluble    = FilePath -> SDoc
text "Insoluble"
  ppr IC_BadTelescope = FilePath -> SDoc
text "Bad telescope"
  ppr IC_Unsolved     = FilePath -> SDoc
text "Unsolved"
  ppr (IC_Solved { ics_dead :: ImplicStatus -> [TyVar]
ics_dead = [TyVar]
dead })
    = FilePath -> SDoc
text "Solved" SDoc -> SDoc -> SDoc
<+> (SDoc -> SDoc
braces (FilePath -> SDoc
text "Dead givens =" SDoc -> SDoc -> SDoc
<+> [TyVar] -> SDoc
forall a. Outputable a => a -> SDoc
ppr [TyVar]
dead))

{-
Note [Needed evidence variables]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Th ic_need_evs field holds the free vars of ic_binds, and all the
ic_binds in nested implications.

  * Main purpose: if one of the ic_givens is not mentioned in here, it
    is redundant.

  * solveImplication may drop an implication altogether if it has no
    remaining 'wanteds'. But we still track the free vars of its
    evidence binds, even though it has now disappeared.

Note [Shadowing in a constraint]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
We assume NO SHADOWING in a constraint.  Specifically
 * The unification variables are all implicitly quantified at top
   level, and are all unique
 * The skolem variables bound in ic_skols are all freah when the
   implication is created.
So we can safely substitute. For example, if we have
   forall a.  a~Int => ...(forall b. ...a...)...
we can push the (a~Int) constraint inwards in the "givens" without
worrying that 'b' might clash.

Note [Skolems in an implication]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
The skolems in an implication are not there to perform a skolem escape
check.  That happens because all the environment variables are in the
untouchables, and therefore cannot be unified with anything at all,
let alone the skolems.

Instead, ic_skols is used only when considering floating a constraint
outside the implication in TcSimplify.floatEqualities or
TcSimplify.approximateImplications

Note [Insoluble constraints]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Some of the errors that we get during canonicalization are best
reported when all constraints have been simplified as much as
possible. For instance, assume that during simplification the
following constraints arise:

 [Wanted]   F alpha ~  uf1
 [Wanted]   beta ~ uf1 beta

When canonicalizing the wanted (beta ~ uf1 beta), if we eagerly fail
we will simply see a message:
    'Can't construct the infinite type  beta ~ uf1 beta'
and the user has no idea what the uf1 variable is.

Instead our plan is that we will NOT fail immediately, but:
    (1) Record the "frozen" error in the ic_insols field
    (2) Isolate the offending constraint from the rest of the inerts
    (3) Keep on simplifying/canonicalizing

At the end, we will hopefully have substituted uf1 := F alpha, and we
will be able to report a more informative error:
    'Can't construct the infinite type beta ~ F alpha beta'

Insoluble constraints *do* include Derived constraints. For example,
a functional dependency might give rise to [D] Int ~ Bool, and we must
report that.  If insolubles did not contain Deriveds, reportErrors would
never see it.


************************************************************************
*                                                                      *
            Pretty printing
*                                                                      *
************************************************************************
-}

pprEvVars :: [EvVar] -> SDoc    -- Print with their types
pprEvVars :: [TyVar] -> SDoc
pprEvVars ev_vars :: [TyVar]
ev_vars = [SDoc] -> SDoc
vcat ((TyVar -> SDoc) -> [TyVar] -> [SDoc]
forall a b. (a -> b) -> [a] -> [b]
map TyVar -> SDoc
pprEvVarWithType [TyVar]
ev_vars)

pprEvVarTheta :: [EvVar] -> SDoc
pprEvVarTheta :: [TyVar] -> SDoc
pprEvVarTheta ev_vars :: [TyVar]
ev_vars = [Type] -> SDoc
pprTheta ((TyVar -> Type) -> [TyVar] -> [Type]
forall a b. (a -> b) -> [a] -> [b]
map TyVar -> Type
evVarPred [TyVar]
ev_vars)

pprEvVarWithType :: EvVar -> SDoc
pprEvVarWithType :: TyVar -> SDoc
pprEvVarWithType v :: TyVar
v = TyVar -> SDoc
forall a. Outputable a => a -> SDoc
ppr TyVar
v SDoc -> SDoc -> SDoc
<+> SDoc
dcolon SDoc -> SDoc -> SDoc
<+> Type -> SDoc
pprType (TyVar -> Type
evVarPred TyVar
v)



-- | Wraps the given type with the constraints (via ic_given) in the given
-- implication, according to the variables mentioned (via ic_skols)
-- in the implication, but taking care to only wrap those variables
-- that are mentioned in the type or the implication.
wrapTypeWithImplication :: Type -> Implication -> Type
wrapTypeWithImplication :: Type -> Implication -> Type
wrapTypeWithImplication ty :: Type
ty impl :: Implication
impl = Type -> [TyVar] -> [Type] -> Type
wrapType Type
ty [TyVar]
mentioned_skols [Type]
givens
    where givens :: [Type]
givens = (TyVar -> Type) -> [TyVar] -> [Type]
forall a b. (a -> b) -> [a] -> [b]
map TyVar -> Type
idType ([TyVar] -> [Type]) -> [TyVar] -> [Type]
forall a b. (a -> b) -> a -> b
$ Implication -> [TyVar]
ic_given Implication
impl
          skols :: [TyVar]
skols = Implication -> [TyVar]
ic_skols Implication
impl
          freeVars :: TcTyVarSet
freeVars = FV -> TcTyVarSet
fvVarSet (FV -> TcTyVarSet) -> FV -> TcTyVarSet
forall a b. (a -> b) -> a -> b
$ [Type] -> FV
tyCoFVsOfTypes (Type
tyType -> [Type] -> [Type]
forall a. a -> [a] -> [a]
:[Type]
givens)
          mentioned_skols :: [TyVar]
mentioned_skols = (TyVar -> Bool) -> [TyVar] -> [TyVar]
forall a. (a -> Bool) -> [a] -> [a]
filter (TyVar -> TcTyVarSet -> Bool
`elemVarSet` TcTyVarSet
freeVars) [TyVar]
skols

wrapType :: Type -> [TyVar] -> [PredType] -> Type
wrapType :: Type -> [TyVar] -> [Type] -> Type
wrapType ty :: Type
ty skols :: [TyVar]
skols givens :: [Type]
givens = [TyVar] -> Type -> Type
mkSpecForAllTys [TyVar]
skols (Type -> Type) -> Type -> Type
forall a b. (a -> b) -> a -> b
$ [Type] -> Type -> Type
mkFunTys [Type]
givens Type
ty


{-
************************************************************************
*                                                                      *
            CtEvidence
*                                                                      *
************************************************************************

Note [Evidence field of CtEvidence]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
During constraint solving we never look at the type of ctev_evar/ctev_dest;
instead we look at the ctev_pred field.  The evtm/evar field
may be un-zonked.

Note [Bind new Givens immediately]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
For Givens we make new EvVars and bind them immediately. Two main reasons:
  * Gain sharing.  E.g. suppose we start with g :: C a b, where
       class D a => C a b
       class (E a, F a) => D a
    If we generate all g's superclasses as separate EvTerms we might
    get    selD1 (selC1 g) :: E a
           selD2 (selC1 g) :: F a
           selC1 g :: D a
    which we could do more economically as:
           g1 :: D a = selC1 g
           g2 :: E a = selD1 g1
           g3 :: F a = selD2 g1

  * For *coercion* evidence we *must* bind each given:
      class (a~b) => C a b where ....
      f :: C a b => ....
    Then in f's Givens we have g:(C a b) and the superclass sc(g,0):a~b.
    But that superclass selector can't (yet) appear in a coercion
    (see evTermCoercion), so the easy thing is to bind it to an Id.

So a Given has EvVar inside it rather than (as previously) an EvTerm.

-}

-- | A place for type-checking evidence to go after it is generated.
-- Wanted equalities are always HoleDest; other wanteds are always
-- EvVarDest.
data TcEvDest
  = EvVarDest EvVar         -- ^ bind this var to the evidence
              -- EvVarDest is always used for non-type-equalities
              -- e.g. class constraints

  | HoleDest  CoercionHole  -- ^ fill in this hole with the evidence
              -- HoleDest is always used for type-equalities
              -- See Note [Coercion holes] in TyCoRep

data CtEvidence
  = CtGiven    -- Truly given, not depending on subgoals
      { CtEvidence -> Type
ctev_pred :: TcPredType      -- See Note [Ct/evidence invariant]
      , CtEvidence -> TyVar
ctev_evar :: EvVar           -- See Note [Evidence field of CtEvidence]
      , CtEvidence -> CtLoc
ctev_loc  :: CtLoc }


  | CtWanted   -- Wanted goal
      { ctev_pred :: TcPredType     -- See Note [Ct/evidence invariant]
      , CtEvidence -> TcEvDest
ctev_dest :: TcEvDest
      , CtEvidence -> ShadowInfo
ctev_nosh :: ShadowInfo     -- See Note [Constraint flavours]
      , ctev_loc  :: CtLoc }

  | CtDerived  -- A goal that we don't really have to solve and can't
               -- immediately rewrite anything other than a derived
               -- (there's no evidence!) but if we do manage to solve
               -- it may help in solving other goals.
      { ctev_pred :: TcPredType
      , ctev_loc  :: CtLoc }

ctEvPred :: CtEvidence -> TcPredType
-- The predicate of a flavor
ctEvPred :: CtEvidence -> Type
ctEvPred = CtEvidence -> Type
ctev_pred

ctEvLoc :: CtEvidence -> CtLoc
ctEvLoc :: CtEvidence -> CtLoc
ctEvLoc = CtEvidence -> CtLoc
ctev_loc

ctEvOrigin :: CtEvidence -> CtOrigin
ctEvOrigin :: CtEvidence -> CtOrigin
ctEvOrigin = CtLoc -> CtOrigin
ctLocOrigin (CtLoc -> CtOrigin)
-> (CtEvidence -> CtLoc) -> CtEvidence -> CtOrigin
forall b c a. (b -> c) -> (a -> b) -> a -> c
. CtEvidence -> CtLoc
ctEvLoc

-- | Get the equality relation relevant for a 'CtEvidence'
ctEvEqRel :: CtEvidence -> EqRel
ctEvEqRel :: CtEvidence -> EqRel
ctEvEqRel = Type -> EqRel
predTypeEqRel (Type -> EqRel) -> (CtEvidence -> Type) -> CtEvidence -> EqRel
forall b c a. (b -> c) -> (a -> b) -> a -> c
. CtEvidence -> Type
ctEvPred

-- | Get the role relevant for a 'CtEvidence'
ctEvRole :: CtEvidence -> Role
ctEvRole :: CtEvidence -> Role
ctEvRole = EqRel -> Role
eqRelRole (EqRel -> Role) -> (CtEvidence -> EqRel) -> CtEvidence -> Role
forall b c a. (b -> c) -> (a -> b) -> a -> c
. CtEvidence -> EqRel
ctEvEqRel

ctEvTerm :: CtEvidence -> EvTerm
ctEvTerm :: CtEvidence -> EvTerm
ctEvTerm ev :: CtEvidence
ev = EvExpr -> EvTerm
EvExpr (CtEvidence -> EvExpr
ctEvExpr CtEvidence
ev)

ctEvExpr :: CtEvidence -> EvExpr
ctEvExpr :: CtEvidence -> EvExpr
ctEvExpr ev :: CtEvidence
ev@(CtWanted { ctev_dest :: CtEvidence -> TcEvDest
ctev_dest = HoleDest _ })
            = Coercion -> EvExpr
forall b. Coercion -> Expr b
Coercion (Coercion -> EvExpr) -> Coercion -> EvExpr
forall a b. (a -> b) -> a -> b
$ HasDebugCallStack => CtEvidence -> Coercion
CtEvidence -> Coercion
ctEvCoercion CtEvidence
ev
ctEvExpr ev :: CtEvidence
ev = TyVar -> EvExpr
evId (CtEvidence -> TyVar
ctEvEvId CtEvidence
ev)

ctEvCoercion :: HasDebugCallStack => CtEvidence -> Coercion
ctEvCoercion :: CtEvidence -> Coercion
ctEvCoercion (CtGiven { ctev_evar :: CtEvidence -> TyVar
ctev_evar = TyVar
ev_id })
  = TyVar -> Coercion
mkTcCoVarCo TyVar
ev_id
ctEvCoercion (CtWanted { ctev_dest :: CtEvidence -> TcEvDest
ctev_dest = TcEvDest
dest })
  | HoleDest hole :: CoercionHole
hole <- TcEvDest
dest
  = -- ctEvCoercion is only called on type equalities
    -- and they always have HoleDests
    CoercionHole -> Coercion
mkHoleCo CoercionHole
hole
ctEvCoercion ev :: CtEvidence
ev
  = FilePath -> SDoc -> Coercion
forall a. HasCallStack => FilePath -> SDoc -> a
pprPanic "ctEvCoercion" (CtEvidence -> SDoc
forall a. Outputable a => a -> SDoc
ppr CtEvidence
ev)

ctEvEvId :: CtEvidence -> EvVar
ctEvEvId :: CtEvidence -> TyVar
ctEvEvId (CtWanted { ctev_dest :: CtEvidence -> TcEvDest
ctev_dest = EvVarDest ev :: TyVar
ev }) = TyVar
ev
ctEvEvId (CtWanted { ctev_dest :: CtEvidence -> TcEvDest
ctev_dest = HoleDest h :: CoercionHole
h })   = CoercionHole -> TyVar
coHoleCoVar CoercionHole
h
ctEvEvId (CtGiven  { ctev_evar :: CtEvidence -> TyVar
ctev_evar = TyVar
ev })           = TyVar
ev
ctEvEvId ctev :: CtEvidence
ctev@(CtDerived {}) = FilePath -> SDoc -> TyVar
forall a. HasCallStack => FilePath -> SDoc -> a
pprPanic "ctEvId:" (CtEvidence -> SDoc
forall a. Outputable a => a -> SDoc
ppr CtEvidence
ctev)

instance Outputable TcEvDest where
  ppr :: TcEvDest -> SDoc
ppr (HoleDest h :: CoercionHole
h)   = FilePath -> SDoc
text "hole" SDoc -> SDoc -> SDoc
<> CoercionHole -> SDoc
forall a. Outputable a => a -> SDoc
ppr CoercionHole
h
  ppr (EvVarDest ev :: TyVar
ev) = TyVar -> SDoc
forall a. Outputable a => a -> SDoc
ppr TyVar
ev

instance Outputable CtEvidence where
  ppr :: CtEvidence -> SDoc
ppr ev :: CtEvidence
ev = CtFlavour -> SDoc
forall a. Outputable a => a -> SDoc
ppr (CtEvidence -> CtFlavour
ctEvFlavour CtEvidence
ev)
           SDoc -> SDoc -> SDoc
<+> SDoc
pp_ev
           SDoc -> SDoc -> SDoc
<+> SDoc -> SDoc
braces (SubGoalDepth -> SDoc
forall a. Outputable a => a -> SDoc
ppr (CtLoc -> SubGoalDepth
ctl_depth (CtEvidence -> CtLoc
ctEvLoc CtEvidence
ev))) SDoc -> SDoc -> SDoc
<> SDoc
dcolon
                  -- Show the sub-goal depth too
           SDoc -> SDoc -> SDoc
<+> Type -> SDoc
forall a. Outputable a => a -> SDoc
ppr (CtEvidence -> Type
ctEvPred CtEvidence
ev)
    where
      pp_ev :: SDoc
pp_ev = case CtEvidence
ev of
             CtGiven { ctev_evar :: CtEvidence -> TyVar
ctev_evar = TyVar
v } -> TyVar -> SDoc
forall a. Outputable a => a -> SDoc
ppr TyVar
v
             CtWanted {ctev_dest :: CtEvidence -> TcEvDest
ctev_dest = TcEvDest
d } -> TcEvDest -> SDoc
forall a. Outputable a => a -> SDoc
ppr TcEvDest
d
             CtDerived {}              -> FilePath -> SDoc
text "_"

isWanted :: CtEvidence -> Bool
isWanted :: CtEvidence -> Bool
isWanted (CtWanted {}) = Bool
True
isWanted _ = Bool
False

isGiven :: CtEvidence -> Bool
isGiven :: CtEvidence -> Bool
isGiven (CtGiven {})  = Bool
True
isGiven _ = Bool
False

isDerived :: CtEvidence -> Bool
isDerived :: CtEvidence -> Bool
isDerived (CtDerived {}) = Bool
True
isDerived _              = Bool
False

{-
%************************************************************************
%*                                                                      *
            CtFlavour
%*                                                                      *
%************************************************************************

Note [Constraint flavours]
~~~~~~~~~~~~~~~~~~~~~~~~~~
Constraints come in four flavours:

* [G] Given: we have evidence

* [W] Wanted WOnly: we want evidence

* [D] Derived: any solution must satisfy this constraint, but
      we don't need evidence for it.  Examples include:
        - superclasses of [W] class constraints
        - equalities arising from functional dependencies
          or injectivity

* [WD] Wanted WDeriv: a single constraint that represents
                      both [W] and [D]
  We keep them paired as one both for efficiency, and because
  when we have a finite map  F tys -> CFunEqCan, it's inconvenient
  to have two CFunEqCans in the range

The ctev_nosh field of a Wanted distinguishes between [W] and [WD]

Wanted constraints are born as [WD], but are split into [W] and its
"shadow" [D] in TcSMonad.maybeEmitShadow.

See Note [The improvement story and derived shadows] in TcSMonad
-}

data CtFlavour  -- See Note [Constraint flavours]
  = Given
  | Wanted ShadowInfo
  | Derived
  deriving CtFlavour -> CtFlavour -> Bool
(CtFlavour -> CtFlavour -> Bool)
-> (CtFlavour -> CtFlavour -> Bool) -> Eq CtFlavour
forall a. (a -> a -> Bool) -> (a -> a -> Bool) -> Eq a
/= :: CtFlavour -> CtFlavour -> Bool
$c/= :: CtFlavour -> CtFlavour -> Bool
== :: CtFlavour -> CtFlavour -> Bool
$c== :: CtFlavour -> CtFlavour -> Bool
Eq

data ShadowInfo
  = WDeriv   -- [WD] This Wanted constraint has no Derived shadow,
             -- so it behaves like a pair of a Wanted and a Derived
  | WOnly    -- [W] It has a separate derived shadow
             -- See Note [Derived shadows]
  deriving( ShadowInfo -> ShadowInfo -> Bool
(ShadowInfo -> ShadowInfo -> Bool)
-> (ShadowInfo -> ShadowInfo -> Bool) -> Eq ShadowInfo
forall a. (a -> a -> Bool) -> (a -> a -> Bool) -> Eq a
/= :: ShadowInfo -> ShadowInfo -> Bool
$c/= :: ShadowInfo -> ShadowInfo -> Bool
== :: ShadowInfo -> ShadowInfo -> Bool
$c== :: ShadowInfo -> ShadowInfo -> Bool
Eq )

isGivenOrWDeriv :: CtFlavour -> Bool
isGivenOrWDeriv :: CtFlavour -> Bool
isGivenOrWDeriv Given           = Bool
True
isGivenOrWDeriv (Wanted WDeriv) = Bool
True
isGivenOrWDeriv _               = Bool
False

instance Outputable CtFlavour where
  ppr :: CtFlavour -> SDoc
ppr Given           = FilePath -> SDoc
text "[G]"
  ppr (Wanted WDeriv) = FilePath -> SDoc
text "[WD]"
  ppr (Wanted WOnly)  = FilePath -> SDoc
text "[W]"
  ppr Derived         = FilePath -> SDoc
text "[D]"

ctEvFlavour :: CtEvidence -> CtFlavour
ctEvFlavour :: CtEvidence -> CtFlavour
ctEvFlavour (CtWanted { ctev_nosh :: CtEvidence -> ShadowInfo
ctev_nosh = ShadowInfo
nosh }) = ShadowInfo -> CtFlavour
Wanted ShadowInfo
nosh
ctEvFlavour (CtGiven {})                    = CtFlavour
Given
ctEvFlavour (CtDerived {})                  = CtFlavour
Derived

-- | Whether or not one 'Ct' can rewrite another is determined by its
-- flavour and its equality relation. See also
-- Note [Flavours with roles] in TcSMonad
type CtFlavourRole = (CtFlavour, EqRel)

-- | Extract the flavour, role, and boxity from a 'CtEvidence'
ctEvFlavourRole :: CtEvidence -> CtFlavourRole
ctEvFlavourRole :: CtEvidence -> CtFlavourRole
ctEvFlavourRole ev :: CtEvidence
ev = (CtEvidence -> CtFlavour
ctEvFlavour CtEvidence
ev, CtEvidence -> EqRel
ctEvEqRel CtEvidence
ev)

-- | Extract the flavour and role from a 'Ct'
ctFlavourRole :: Ct -> CtFlavourRole
-- Uses short-cuts to role for special cases
ctFlavourRole :: Ct -> CtFlavourRole
ctFlavourRole (CDictCan { cc_ev :: Ct -> CtEvidence
cc_ev = CtEvidence
ev })
  = (CtEvidence -> CtFlavour
ctEvFlavour CtEvidence
ev, EqRel
NomEq)
ctFlavourRole (CTyEqCan { cc_ev :: Ct -> CtEvidence
cc_ev = CtEvidence
ev, cc_eq_rel :: Ct -> EqRel
cc_eq_rel = EqRel
eq_rel })
  = (CtEvidence -> CtFlavour
ctEvFlavour CtEvidence
ev, EqRel
eq_rel)
ctFlavourRole (CFunEqCan { cc_ev :: Ct -> CtEvidence
cc_ev = CtEvidence
ev })
  = (CtEvidence -> CtFlavour
ctEvFlavour CtEvidence
ev, EqRel
NomEq)
ctFlavourRole (CHoleCan { cc_ev :: Ct -> CtEvidence
cc_ev = CtEvidence
ev })
  = (CtEvidence -> CtFlavour
ctEvFlavour CtEvidence
ev, EqRel
NomEq)  -- NomEq: CHoleCans can be rewritten by
                             -- by nominal equalities but empahatically
                             -- not by representational equalities
ctFlavourRole ct :: Ct
ct
  = CtEvidence -> CtFlavourRole
ctEvFlavourRole (Ct -> CtEvidence
ctEvidence Ct
ct)

{- Note [eqCanRewrite]
~~~~~~~~~~~~~~~~~~~~~~
(eqCanRewrite ct1 ct2) holds if the constraint ct1 (a CTyEqCan of form
tv ~ ty) can be used to rewrite ct2.  It must satisfy the properties of
a can-rewrite relation, see Definition [Can-rewrite relation] in
TcSMonad.

With the solver handling Coercible constraints like equality constraints,
the rewrite conditions must take role into account, never allowing
a representational equality to rewrite a nominal one.

Note [Wanteds do not rewrite Wanteds]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
We don't allow Wanteds to rewrite Wanteds, because that can give rise
to very confusing type error messages.  A good example is Trac #8450.
Here's another
   f :: a -> Bool
   f x = ( [x,'c'], [x,True] ) `seq` True
Here we get
  [W] a ~ Char
  [W] a ~ Bool
but we do not want to complain about Bool ~ Char!

Note [Deriveds do rewrite Deriveds]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
However we DO allow Deriveds to rewrite Deriveds, because that's how
improvement works; see Note [The improvement story] in TcInteract.

However, for now at least I'm only letting (Derived,NomEq) rewrite
(Derived,NomEq) and not doing anything for ReprEq.  If we have
    eqCanRewriteFR (Derived, NomEq) (Derived, _)  = True
then we lose property R2 of Definition [Can-rewrite relation]
in TcSMonad
  R2.  If f1 >= f, and f2 >= f,
       then either f1 >= f2 or f2 >= f1
Consider f1 = (Given, ReprEq)
         f2 = (Derived, NomEq)
          f = (Derived, ReprEq)

I thought maybe we could never get Derived ReprEq constraints, but
we can; straight from the Wanteds during improvement. And from a Derived
ReprEq we could conceivably get a Derived NomEq improvement (by decomposing
a type constructor with Nomninal role), and hence unify.
-}

eqCanRewrite :: EqRel -> EqRel -> Bool
eqCanRewrite :: EqRel -> EqRel -> Bool
eqCanRewrite NomEq  _      = Bool
True
eqCanRewrite ReprEq ReprEq = Bool
True
eqCanRewrite ReprEq NomEq  = Bool
False

eqCanRewriteFR :: CtFlavourRole -> CtFlavourRole -> Bool
-- Can fr1 actually rewrite fr2?
-- Very important function!
-- See Note [eqCanRewrite]
-- See Note [Wanteds do not rewrite Wanteds]
-- See Note [Deriveds do rewrite Deriveds]
eqCanRewriteFR :: CtFlavourRole -> CtFlavourRole -> Bool
eqCanRewriteFR (Given,         r1 :: EqRel
r1)    (_,       r2 :: EqRel
r2)    = EqRel -> EqRel -> Bool
eqCanRewrite EqRel
r1 EqRel
r2
eqCanRewriteFR (Wanted WDeriv, NomEq) (Derived, NomEq) = Bool
True
eqCanRewriteFR (Derived,       NomEq) (Derived, NomEq) = Bool
True
eqCanRewriteFR _                      _                = Bool
False

eqMayRewriteFR :: CtFlavourRole -> CtFlavourRole -> Bool
-- Is it /possible/ that fr1 can rewrite fr2?
-- This is used when deciding which inerts to kick out,
-- at which time a [WD] inert may be split into [W] and [D]
eqMayRewriteFR :: CtFlavourRole -> CtFlavourRole -> Bool
eqMayRewriteFR (Wanted WDeriv, NomEq) (Wanted WDeriv, NomEq) = Bool
True
eqMayRewriteFR (Derived,       NomEq) (Wanted WDeriv, NomEq) = Bool
True
eqMayRewriteFR fr1 :: CtFlavourRole
fr1 fr2 :: CtFlavourRole
fr2 = CtFlavourRole -> CtFlavourRole -> Bool
eqCanRewriteFR CtFlavourRole
fr1 CtFlavourRole
fr2

-----------------
{- Note [funEqCanDischarge]
~~~~~~~~~~~~~~~~~~~~~~~~~~~
Suppose we have two CFunEqCans with the same LHS:
    (x1:F ts ~ f1) `funEqCanDischarge` (x2:F ts ~ f2)
Can we drop x2 in favour of x1, either unifying
f2 (if it's a flatten meta-var) or adding a new Given
(f1 ~ f2), if x2 is a Given?

Answer: yes if funEqCanDischarge is true.
-}

funEqCanDischarge
  :: CtEvidence -> CtEvidence
  -> ( SwapFlag   -- NotSwapped => lhs can discharge rhs
                  -- Swapped    => rhs can discharge lhs
     , Bool)      -- True <=> upgrade non-discharded one
                  --          from [W] to [WD]
-- See Note [funEqCanDischarge]
funEqCanDischarge :: CtEvidence -> CtEvidence -> (SwapFlag, Bool)
funEqCanDischarge ev1 :: CtEvidence
ev1 ev2 :: CtEvidence
ev2
  = ASSERT2( ctEvEqRel ev1 == NomEq, ppr ev1 )
    ASSERT2( ctEvEqRel ev2 == NomEq, ppr ev2 )
    -- CFunEqCans are all Nominal, hence asserts
    CtFlavour -> CtFlavour -> (SwapFlag, Bool)
funEqCanDischargeF (CtEvidence -> CtFlavour
ctEvFlavour CtEvidence
ev1) (CtEvidence -> CtFlavour
ctEvFlavour CtEvidence
ev2)

funEqCanDischargeF :: CtFlavour -> CtFlavour -> (SwapFlag, Bool)
funEqCanDischargeF :: CtFlavour -> CtFlavour -> (SwapFlag, Bool)
funEqCanDischargeF Given           _               = (SwapFlag
NotSwapped, Bool
False)
funEqCanDischargeF _               Given           = (SwapFlag
IsSwapped,  Bool
False)
funEqCanDischargeF (Wanted WDeriv) _               = (SwapFlag
NotSwapped, Bool
False)
funEqCanDischargeF _               (Wanted WDeriv) = (SwapFlag
IsSwapped,  Bool
True)
funEqCanDischargeF (Wanted WOnly)  (Wanted WOnly)  = (SwapFlag
NotSwapped, Bool
False)
funEqCanDischargeF (Wanted WOnly)  Derived         = (SwapFlag
NotSwapped, Bool
True)
funEqCanDischargeF Derived         (Wanted WOnly)  = (SwapFlag
IsSwapped,  Bool
True)
funEqCanDischargeF Derived         Derived         = (SwapFlag
NotSwapped, Bool
False)


{- Note [eqCanDischarge]
~~~~~~~~~~~~~~~~~~~~~~~~
Suppose we have two identical CTyEqCan equality constraints
(i.e. both LHS and RHS are the same)
      (x1:a~t) `eqCanDischarge` (xs:a~t)
Can we just drop x2 in favour of x1?

Answer: yes if eqCanDischarge is true.

Note that we do /not/ allow Wanted to discharge Derived.
We must keep both.  Why?  Because the Derived may rewrite
other Deriveds in the model whereas the Wanted cannot.

However a Wanted can certainly discharge an identical Wanted.  So
eqCanDischarge does /not/ define a can-rewrite relation in the
sense of Definition [Can-rewrite relation] in TcSMonad.

We /do/ say that a [W] can discharge a [WD].  In evidence terms it
certainly can, and the /caller/ arranges that the otherwise-lost [D]
is spat out as a new Derived.  -}

eqCanDischargeFR :: CtFlavourRole -> CtFlavourRole -> Bool
-- See Note [eqCanDischarge]
eqCanDischargeFR :: CtFlavourRole -> CtFlavourRole -> Bool
eqCanDischargeFR (f1 :: CtFlavour
f1,r1 :: EqRel
r1) (f2 :: CtFlavour
f2, r2 :: EqRel
r2) =  EqRel -> EqRel -> Bool
eqCanRewrite EqRel
r1 EqRel
r2
                                  Bool -> Bool -> Bool
&& CtFlavour -> CtFlavour -> Bool
eqCanDischargeF CtFlavour
f1 CtFlavour
f2

eqCanDischargeF :: CtFlavour -> CtFlavour -> Bool
eqCanDischargeF :: CtFlavour -> CtFlavour -> Bool
eqCanDischargeF Given   _                  = Bool
True
eqCanDischargeF (Wanted _)      (Wanted _) = Bool
True
eqCanDischargeF (Wanted WDeriv) Derived    = Bool
True
eqCanDischargeF Derived         Derived    = Bool
True
eqCanDischargeF _               _          = Bool
False


{-
************************************************************************
*                                                                      *
            SubGoalDepth
*                                                                      *
************************************************************************

Note [SubGoalDepth]
~~~~~~~~~~~~~~~~~~~
The 'SubGoalDepth' takes care of stopping the constraint solver from looping.

The counter starts at zero and increases. It includes dictionary constraints,
equality simplification, and type family reduction. (Why combine these? Because
it's actually quite easy to mistake one for another, in sufficiently involved
scenarios, like ConstraintKinds.)

The flag -fcontext-stack=n (not very well named!) fixes the maximium
level.

* The counter includes the depth of type class instance declarations.  Example:
     [W] d{7} : Eq [Int]
  That is d's dictionary-constraint depth is 7.  If we use the instance
     $dfEqList :: Eq a => Eq [a]
  to simplify it, we get
     d{7} = $dfEqList d'{8}
  where d'{8} : Eq Int, and d' has depth 8.

  For civilised (decidable) instance declarations, each increase of
  depth removes a type constructor from the type, so the depth never
  gets big; i.e. is bounded by the structural depth of the type.

* The counter also increments when resolving
equalities involving type functions. Example:
  Assume we have a wanted at depth 7:
    [W] d{7} : F () ~ a
  If there is a type function equation "F () = Int", this would be rewritten to
    [W] d{8} : Int ~ a
  and remembered as having depth 8.

  Again, without UndecidableInstances, this counter is bounded, but without it
  can resolve things ad infinitum. Hence there is a maximum level.

* Lastly, every time an equality is rewritten, the counter increases. Again,
  rewriting an equality constraint normally makes progress, but it's possible
  the "progress" is just the reduction of an infinitely-reducing type family.
  Hence we need to track the rewrites.

When compiling a program requires a greater depth, then GHC recommends turning
off this check entirely by setting -freduction-depth=0. This is because the
exact number that works is highly variable, and is likely to change even between
minor releases. Because this check is solely to prevent infinite compilation
times, it seems safe to disable it when a user has ascertained that their program
doesn't loop at the type level.

-}

-- | See Note [SubGoalDepth]
newtype SubGoalDepth = SubGoalDepth Int
  deriving (SubGoalDepth -> SubGoalDepth -> Bool
(SubGoalDepth -> SubGoalDepth -> Bool)
-> (SubGoalDepth -> SubGoalDepth -> Bool) -> Eq SubGoalDepth
forall a. (a -> a -> Bool) -> (a -> a -> Bool) -> Eq a
/= :: SubGoalDepth -> SubGoalDepth -> Bool
$c/= :: SubGoalDepth -> SubGoalDepth -> Bool
== :: SubGoalDepth -> SubGoalDepth -> Bool
$c== :: SubGoalDepth -> SubGoalDepth -> Bool
Eq, Eq SubGoalDepth
Eq SubGoalDepth =>
(SubGoalDepth -> SubGoalDepth -> Ordering)
-> (SubGoalDepth -> SubGoalDepth -> Bool)
-> (SubGoalDepth -> SubGoalDepth -> Bool)
-> (SubGoalDepth -> SubGoalDepth -> Bool)
-> (SubGoalDepth -> SubGoalDepth -> Bool)
-> (SubGoalDepth -> SubGoalDepth -> SubGoalDepth)
-> (SubGoalDepth -> SubGoalDepth -> SubGoalDepth)
-> Ord SubGoalDepth
SubGoalDepth -> SubGoalDepth -> Bool
SubGoalDepth -> SubGoalDepth -> Ordering
SubGoalDepth -> SubGoalDepth -> SubGoalDepth
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 :: SubGoalDepth -> SubGoalDepth -> SubGoalDepth
$cmin :: SubGoalDepth -> SubGoalDepth -> SubGoalDepth
max :: SubGoalDepth -> SubGoalDepth -> SubGoalDepth
$cmax :: SubGoalDepth -> SubGoalDepth -> SubGoalDepth
>= :: SubGoalDepth -> SubGoalDepth -> Bool
$c>= :: SubGoalDepth -> SubGoalDepth -> Bool
> :: SubGoalDepth -> SubGoalDepth -> Bool
$c> :: SubGoalDepth -> SubGoalDepth -> Bool
<= :: SubGoalDepth -> SubGoalDepth -> Bool
$c<= :: SubGoalDepth -> SubGoalDepth -> Bool
< :: SubGoalDepth -> SubGoalDepth -> Bool
$c< :: SubGoalDepth -> SubGoalDepth -> Bool
compare :: SubGoalDepth -> SubGoalDepth -> Ordering
$ccompare :: SubGoalDepth -> SubGoalDepth -> Ordering
$cp1Ord :: Eq SubGoalDepth
Ord, Rational -> SubGoalDepth -> SDoc
SubGoalDepth -> SDoc
(SubGoalDepth -> SDoc)
-> (Rational -> SubGoalDepth -> SDoc) -> Outputable SubGoalDepth
forall a. (a -> SDoc) -> (Rational -> a -> SDoc) -> Outputable a
pprPrec :: Rational -> SubGoalDepth -> SDoc
$cpprPrec :: Rational -> SubGoalDepth -> SDoc
ppr :: SubGoalDepth -> SDoc
$cppr :: SubGoalDepth -> SDoc
Outputable)

initialSubGoalDepth :: SubGoalDepth
initialSubGoalDepth :: SubGoalDepth
initialSubGoalDepth = Int -> SubGoalDepth
SubGoalDepth 0

bumpSubGoalDepth :: SubGoalDepth -> SubGoalDepth
bumpSubGoalDepth :: SubGoalDepth -> SubGoalDepth
bumpSubGoalDepth (SubGoalDepth n :: Int
n) = Int -> SubGoalDepth
SubGoalDepth (Int
n Int -> Int -> Int
forall a. Num a => a -> a -> a
+ 1)

maxSubGoalDepth :: SubGoalDepth -> SubGoalDepth -> SubGoalDepth
maxSubGoalDepth :: SubGoalDepth -> SubGoalDepth -> SubGoalDepth
maxSubGoalDepth (SubGoalDepth n :: Int
n) (SubGoalDepth m :: Int
m) = Int -> SubGoalDepth
SubGoalDepth (Int
n Int -> Int -> Int
forall a. Ord a => a -> a -> a
`max` Int
m)

subGoalDepthExceeded :: DynFlags -> SubGoalDepth -> Bool
subGoalDepthExceeded :: DynFlags -> SubGoalDepth -> Bool
subGoalDepthExceeded dflags :: DynFlags
dflags (SubGoalDepth d :: Int
d)
  = Int -> IntWithInf
mkIntWithInf Int
d IntWithInf -> IntWithInf -> Bool
forall a. Ord a => a -> a -> Bool
> DynFlags -> IntWithInf
reductionDepth DynFlags
dflags

{-
************************************************************************
*                                                                      *
            CtLoc
*                                                                      *
************************************************************************

The 'CtLoc' gives information about where a constraint came from.
This is important for decent error message reporting because
dictionaries don't appear in the original source code.
type will evolve...

-}

data CtLoc = CtLoc { CtLoc -> CtOrigin
ctl_origin :: CtOrigin
                   , CtLoc -> TcLclEnv
ctl_env    :: TcLclEnv
                   , CtLoc -> Maybe TypeOrKind
ctl_t_or_k :: Maybe TypeOrKind  -- OK if we're not sure
                   , CtLoc -> SubGoalDepth
ctl_depth  :: !SubGoalDepth }

  -- The TcLclEnv includes particularly
  --    source location:  tcl_loc   :: RealSrcSpan
  --    context:          tcl_ctxt  :: [ErrCtxt]
  --    binder stack:     tcl_bndrs :: TcBinderStack
  --    level:            tcl_tclvl :: TcLevel

mkKindLoc :: TcType -> TcType   -- original *types* being compared
          -> CtLoc -> CtLoc
mkKindLoc :: Type -> Type -> CtLoc -> CtLoc
mkKindLoc s1 :: Type
s1 s2 :: Type
s2 loc :: CtLoc
loc = CtLoc -> CtOrigin -> CtLoc
setCtLocOrigin (CtLoc -> CtLoc
toKindLoc CtLoc
loc)
                        (Type -> Maybe Type -> CtOrigin -> Maybe TypeOrKind -> CtOrigin
KindEqOrigin Type
s1 (Type -> Maybe Type
forall a. a -> Maybe a
Just Type
s2) (CtLoc -> CtOrigin
ctLocOrigin CtLoc
loc)
                                      (CtLoc -> Maybe TypeOrKind
ctLocTypeOrKind_maybe CtLoc
loc))

-- | Take a CtLoc and moves it to the kind level
toKindLoc :: CtLoc -> CtLoc
toKindLoc :: CtLoc -> CtLoc
toKindLoc loc :: CtLoc
loc = CtLoc
loc { ctl_t_or_k :: Maybe TypeOrKind
ctl_t_or_k = TypeOrKind -> Maybe TypeOrKind
forall a. a -> Maybe a
Just TypeOrKind
KindLevel }

mkGivenLoc :: TcLevel -> SkolemInfo -> TcLclEnv -> CtLoc
mkGivenLoc :: TcLevel -> SkolemInfo -> TcLclEnv -> CtLoc
mkGivenLoc tclvl :: TcLevel
tclvl skol_info :: SkolemInfo
skol_info env :: TcLclEnv
env
  = $WCtLoc :: CtOrigin -> TcLclEnv -> Maybe TypeOrKind -> SubGoalDepth -> CtLoc
CtLoc { ctl_origin :: CtOrigin
ctl_origin = SkolemInfo -> CtOrigin
GivenOrigin SkolemInfo
skol_info
          , ctl_env :: TcLclEnv
ctl_env    = TcLclEnv
env { tcl_tclvl :: TcLevel
tcl_tclvl = TcLevel
tclvl }
          , ctl_t_or_k :: Maybe TypeOrKind
ctl_t_or_k = Maybe TypeOrKind
forall a. Maybe a
Nothing    -- this only matters for error msgs
          , ctl_depth :: SubGoalDepth
ctl_depth  = SubGoalDepth
initialSubGoalDepth }

ctLocEnv :: CtLoc -> TcLclEnv
ctLocEnv :: CtLoc -> TcLclEnv
ctLocEnv = CtLoc -> TcLclEnv
ctl_env

ctLocLevel :: CtLoc -> TcLevel
ctLocLevel :: CtLoc -> TcLevel
ctLocLevel loc :: CtLoc
loc = TcLclEnv -> TcLevel
tcl_tclvl (CtLoc -> TcLclEnv
ctLocEnv CtLoc
loc)

ctLocDepth :: CtLoc -> SubGoalDepth
ctLocDepth :: CtLoc -> SubGoalDepth
ctLocDepth = CtLoc -> SubGoalDepth
ctl_depth

ctLocOrigin :: CtLoc -> CtOrigin
ctLocOrigin :: CtLoc -> CtOrigin
ctLocOrigin = CtLoc -> CtOrigin
ctl_origin

ctLocSpan :: CtLoc -> RealSrcSpan
ctLocSpan :: CtLoc -> RealSrcSpan
ctLocSpan (CtLoc { ctl_env :: CtLoc -> TcLclEnv
ctl_env = TcLclEnv
lcl}) = TcLclEnv -> RealSrcSpan
tcl_loc TcLclEnv
lcl

ctLocTypeOrKind_maybe :: CtLoc -> Maybe TypeOrKind
ctLocTypeOrKind_maybe :: CtLoc -> Maybe TypeOrKind
ctLocTypeOrKind_maybe = CtLoc -> Maybe TypeOrKind
ctl_t_or_k

setCtLocSpan :: CtLoc -> RealSrcSpan -> CtLoc
setCtLocSpan :: CtLoc -> RealSrcSpan -> CtLoc
setCtLocSpan ctl :: CtLoc
ctl@(CtLoc { ctl_env :: CtLoc -> TcLclEnv
ctl_env = TcLclEnv
lcl }) loc :: RealSrcSpan
loc = CtLoc -> TcLclEnv -> CtLoc
setCtLocEnv CtLoc
ctl (TcLclEnv
lcl { tcl_loc :: RealSrcSpan
tcl_loc = RealSrcSpan
loc })

bumpCtLocDepth :: CtLoc -> CtLoc
bumpCtLocDepth :: CtLoc -> CtLoc
bumpCtLocDepth loc :: CtLoc
loc@(CtLoc { ctl_depth :: CtLoc -> SubGoalDepth
ctl_depth = SubGoalDepth
d }) = CtLoc
loc { ctl_depth :: SubGoalDepth
ctl_depth = SubGoalDepth -> SubGoalDepth
bumpSubGoalDepth SubGoalDepth
d }

setCtLocOrigin :: CtLoc -> CtOrigin -> CtLoc
setCtLocOrigin :: CtLoc -> CtOrigin -> CtLoc
setCtLocOrigin ctl :: CtLoc
ctl orig :: CtOrigin
orig = CtLoc
ctl { ctl_origin :: CtOrigin
ctl_origin = CtOrigin
orig }

updateCtLocOrigin :: CtLoc -> (CtOrigin -> CtOrigin) -> CtLoc
updateCtLocOrigin :: CtLoc -> (CtOrigin -> CtOrigin) -> CtLoc
updateCtLocOrigin ctl :: CtLoc
ctl@(CtLoc { ctl_origin :: CtLoc -> CtOrigin
ctl_origin = CtOrigin
orig }) upd :: CtOrigin -> CtOrigin
upd
  = CtLoc
ctl { ctl_origin :: CtOrigin
ctl_origin = CtOrigin -> CtOrigin
upd CtOrigin
orig }

setCtLocEnv :: CtLoc -> TcLclEnv -> CtLoc
setCtLocEnv :: CtLoc -> TcLclEnv -> CtLoc
setCtLocEnv ctl :: CtLoc
ctl env :: TcLclEnv
env = CtLoc
ctl { ctl_env :: TcLclEnv
ctl_env = TcLclEnv
env }

pushErrCtxt :: CtOrigin -> ErrCtxt -> CtLoc -> CtLoc
pushErrCtxt :: CtOrigin -> ErrCtxt -> CtLoc -> CtLoc
pushErrCtxt o :: CtOrigin
o err :: ErrCtxt
err loc :: CtLoc
loc@(CtLoc { ctl_env :: CtLoc -> TcLclEnv
ctl_env = TcLclEnv
lcl })
  = CtLoc
loc { ctl_origin :: CtOrigin
ctl_origin = CtOrigin
o, ctl_env :: TcLclEnv
ctl_env = TcLclEnv
lcl { tcl_ctxt :: [ErrCtxt]
tcl_ctxt = ErrCtxt
err ErrCtxt -> [ErrCtxt] -> [ErrCtxt]
forall a. a -> [a] -> [a]
: TcLclEnv -> [ErrCtxt]
tcl_ctxt TcLclEnv
lcl } }

pushErrCtxtSameOrigin :: ErrCtxt -> CtLoc -> CtLoc
-- Just add information w/o updating the origin!
pushErrCtxtSameOrigin :: ErrCtxt -> CtLoc -> CtLoc
pushErrCtxtSameOrigin err :: ErrCtxt
err loc :: CtLoc
loc@(CtLoc { ctl_env :: CtLoc -> TcLclEnv
ctl_env = TcLclEnv
lcl })
  = CtLoc
loc { ctl_env :: TcLclEnv
ctl_env = TcLclEnv
lcl { tcl_ctxt :: [ErrCtxt]
tcl_ctxt = ErrCtxt
err ErrCtxt -> [ErrCtxt] -> [ErrCtxt]
forall a. a -> [a] -> [a]
: TcLclEnv -> [ErrCtxt]
tcl_ctxt TcLclEnv
lcl } }

{-
************************************************************************
*                                                                      *
                SkolemInfo
*                                                                      *
************************************************************************
-}

-- SkolemInfo gives the origin of *given* constraints
--   a) type variables are skolemised
--   b) an implication constraint is generated
data SkolemInfo
  = SigSkol -- A skolem that is created by instantiating
            -- a programmer-supplied type signature
            -- Location of the binding site is on the TyVar
            -- See Note [SigSkol SkolemInfo]
       UserTypeCtxt        -- What sort of signature
       TcType              -- Original type signature (before skolemisation)
       [(Name,TcTyVar)]    -- Maps the original name of the skolemised tyvar
                           -- to its instantiated version

  | SigTypeSkol UserTypeCtxt
                 -- like SigSkol, but when we're kind-checking the *type*
                 -- hence, we have less info

  | ForAllSkol SDoc     -- Bound by a user-written "forall".

  | DerivSkol Type      -- Bound by a 'deriving' clause;
                        -- the type is the instance we are trying to derive

  | InstSkol            -- Bound at an instance decl
  | InstSC TypeSize     -- A "given" constraint obtained by superclass selection.
                        -- If (C ty1 .. tyn) is the largest class from
                        --    which we made a superclass selection in the chain,
                        --    then TypeSize = sizeTypes [ty1, .., tyn]
                        -- See Note [Solving superclass constraints] in TcInstDcls

  | FamInstSkol         -- Bound at a family instance decl
  | PatSkol             -- An existential type variable bound by a pattern for
      ConLike           -- a data constructor with an existential type.
      (HsMatchContext Name)
             -- e.g.   data T = forall a. Eq a => MkT a
             --        f (MkT x) = ...
             -- The pattern MkT x will allocate an existential type
             -- variable for 'a'.

  | ArrowSkol           -- An arrow form (see TcArrows)

  | IPSkol [HsIPName]   -- Binding site of an implicit parameter

  | RuleSkol RuleName   -- The LHS of a RULE

  | InferSkol [(Name,TcType)]
                        -- We have inferred a type for these (mutually-recursivive)
                        -- polymorphic Ids, and are now checking that their RHS
                        -- constraints are satisfied.

  | BracketSkol         -- Template Haskell bracket

  | UnifyForAllSkol     -- We are unifying two for-all types
       TcType           -- The instantiated type *inside* the forall

  | TyConSkol TyConFlavour Name  -- bound in a type declaration of the given flavour

  | DataConSkol Name    -- bound as an existential in a Haskell98 datacon decl or
                        -- as any variable in a GADT datacon decl

  | ReifySkol           -- Bound during Template Haskell reification

  | QuantCtxtSkol       -- Quantified context, e.g.
                        --   f :: forall c. (forall a. c a => c [a]) => blah

  | UnkSkol             -- Unhelpful info (until I improve it)

instance Outputable SkolemInfo where
  ppr :: SkolemInfo -> SDoc
ppr = SkolemInfo -> SDoc
pprSkolInfo

pprSkolInfo :: SkolemInfo -> SDoc
-- Complete the sentence "is a rigid type variable bound by..."
pprSkolInfo :: SkolemInfo -> SDoc
pprSkolInfo (SigSkol cx :: UserTypeCtxt
cx ty :: Type
ty _) = UserTypeCtxt -> Type -> SDoc
pprSigSkolInfo UserTypeCtxt
cx Type
ty
pprSkolInfo (SigTypeSkol cx :: UserTypeCtxt
cx)  = UserTypeCtxt -> SDoc
pprUserTypeCtxt UserTypeCtxt
cx
pprSkolInfo (ForAllSkol doc :: SDoc
doc)  = SDoc -> SDoc
quotes SDoc
doc
pprSkolInfo (IPSkol ips :: [HsIPName]
ips)      = FilePath -> SDoc
text "the implicit-parameter binding" SDoc -> SDoc -> SDoc
<> [HsIPName] -> SDoc
forall a. [a] -> SDoc
plural [HsIPName]
ips SDoc -> SDoc -> SDoc
<+> FilePath -> SDoc
text "for"
                                 SDoc -> SDoc -> SDoc
<+> (HsIPName -> SDoc) -> [HsIPName] -> SDoc
forall a. (a -> SDoc) -> [a] -> SDoc
pprWithCommas HsIPName -> SDoc
forall a. Outputable a => a -> SDoc
ppr [HsIPName]
ips
pprSkolInfo (DerivSkol pred :: Type
pred)  = FilePath -> SDoc
text "the deriving clause for" SDoc -> SDoc -> SDoc
<+> SDoc -> SDoc
quotes (Type -> SDoc
forall a. Outputable a => a -> SDoc
ppr Type
pred)
pprSkolInfo InstSkol          = FilePath -> SDoc
text "the instance declaration"
pprSkolInfo (InstSC n :: IntWithInf
n)        = FilePath -> SDoc
text "the instance declaration" SDoc -> SDoc -> SDoc
<> SDoc -> SDoc
whenPprDebug (SDoc -> SDoc
parens (IntWithInf -> SDoc
forall a. Outputable a => a -> SDoc
ppr IntWithInf
n))
pprSkolInfo FamInstSkol       = FilePath -> SDoc
text "a family instance declaration"
pprSkolInfo BracketSkol       = FilePath -> SDoc
text "a Template Haskell bracket"
pprSkolInfo (RuleSkol name :: RuleName
name)   = FilePath -> SDoc
text "the RULE" SDoc -> SDoc -> SDoc
<+> RuleName -> SDoc
pprRuleName RuleName
name
pprSkolInfo ArrowSkol         = FilePath -> SDoc
text "an arrow form"
pprSkolInfo (PatSkol cl :: ConLike
cl mc :: HsMatchContext Name
mc)   = [SDoc] -> SDoc
sep [ ConLike -> SDoc
pprPatSkolInfo ConLike
cl
                                    , FilePath -> SDoc
text "in" SDoc -> SDoc -> SDoc
<+> HsMatchContext Name -> SDoc
forall id.
(Outputable (NameOrRdrName id), Outputable id) =>
HsMatchContext id -> SDoc
pprMatchContext HsMatchContext Name
mc ]
pprSkolInfo (InferSkol ids :: [(Name, Type)]
ids)   = SDoc -> Int -> SDoc -> SDoc
hang (FilePath -> SDoc
text "the inferred type" SDoc -> SDoc -> SDoc
<> [(Name, Type)] -> SDoc
forall a. [a] -> SDoc
plural [(Name, Type)]
ids SDoc -> SDoc -> SDoc
<+> FilePath -> SDoc
text "of")
                                   2 ([SDoc] -> SDoc
vcat [ Name -> SDoc
forall a. Outputable a => a -> SDoc
ppr Name
name SDoc -> SDoc -> SDoc
<+> SDoc
dcolon SDoc -> SDoc -> SDoc
<+> Type -> SDoc
forall a. Outputable a => a -> SDoc
ppr Type
ty
                                                   | (name :: Name
name,ty :: Type
ty) <- [(Name, Type)]
ids ])
pprSkolInfo (UnifyForAllSkol ty :: Type
ty) = FilePath -> SDoc
text "the type" SDoc -> SDoc -> SDoc
<+> Type -> SDoc
forall a. Outputable a => a -> SDoc
ppr Type
ty
pprSkolInfo (TyConSkol flav :: TyConFlavour
flav name :: Name
name) = FilePath -> SDoc
text "the" SDoc -> SDoc -> SDoc
<+> TyConFlavour -> SDoc
forall a. Outputable a => a -> SDoc
ppr TyConFlavour
flav SDoc -> SDoc -> SDoc
<+> FilePath -> SDoc
text "declaration for" SDoc -> SDoc -> SDoc
<+> SDoc -> SDoc
quotes (Name -> SDoc
forall a. Outputable a => a -> SDoc
ppr Name
name)
pprSkolInfo (DataConSkol name :: Name
name)= FilePath -> SDoc
text "the data constructor" SDoc -> SDoc -> SDoc
<+> SDoc -> SDoc
quotes (Name -> SDoc
forall a. Outputable a => a -> SDoc
ppr Name
name)
pprSkolInfo ReifySkol         = FilePath -> SDoc
text "the type being reified"

pprSkolInfo (QuantCtxtSkol {}) = FilePath -> SDoc
text "a quantified context"

-- UnkSkol
-- For type variables the others are dealt with by pprSkolTvBinding.
-- For Insts, these cases should not happen
pprSkolInfo UnkSkol = WARN( True, text "pprSkolInfo: UnkSkol" ) text "UnkSkol"

pprSigSkolInfo :: UserTypeCtxt -> TcType -> SDoc
-- The type is already tidied
pprSigSkolInfo :: UserTypeCtxt -> Type -> SDoc
pprSigSkolInfo ctxt :: UserTypeCtxt
ctxt ty :: Type
ty
  = case UserTypeCtxt
ctxt of
       FunSigCtxt f :: Name
f _ -> [SDoc] -> SDoc
vcat [ FilePath -> SDoc
text "the type signature for:"
                              , Int -> SDoc -> SDoc
nest 2 (Name -> SDoc
forall a. OutputableBndr a => a -> SDoc
pprPrefixOcc Name
f SDoc -> SDoc -> SDoc
<+> SDoc
dcolon SDoc -> SDoc -> SDoc
<+> Type -> SDoc
forall a. Outputable a => a -> SDoc
ppr Type
ty) ]
       PatSynCtxt {}  -> UserTypeCtxt -> SDoc
pprUserTypeCtxt UserTypeCtxt
ctxt  -- See Note [Skolem info for pattern synonyms]
       _              -> [SDoc] -> SDoc
vcat [ UserTypeCtxt -> SDoc
pprUserTypeCtxt UserTypeCtxt
ctxt SDoc -> SDoc -> SDoc
<> SDoc
colon
                              , Int -> SDoc -> SDoc
nest 2 (Type -> SDoc
forall a. Outputable a => a -> SDoc
ppr Type
ty) ]

pprPatSkolInfo :: ConLike -> SDoc
pprPatSkolInfo :: ConLike -> SDoc
pprPatSkolInfo (RealDataCon dc :: DataCon
dc)
  = [SDoc] -> SDoc
sep [ FilePath -> SDoc
text "a pattern with constructor:"
        , Int -> SDoc -> SDoc
nest 2 (SDoc -> SDoc) -> SDoc -> SDoc
forall a b. (a -> b) -> a -> b
$ DataCon -> SDoc
forall a. Outputable a => a -> SDoc
ppr DataCon
dc SDoc -> SDoc -> SDoc
<+> SDoc
dcolon
          SDoc -> SDoc -> SDoc
<+> Type -> SDoc
pprType (DataCon -> Type
dataConUserType DataCon
dc) SDoc -> SDoc -> SDoc
<> SDoc
comma ]
          -- pprType prints forall's regardless of -fprint-explicit-foralls
          -- which is what we want here, since we might be saying
          -- type variable 't' is bound by ...

pprPatSkolInfo (PatSynCon ps :: PatSyn
ps)
  = [SDoc] -> SDoc
sep [ FilePath -> SDoc
text "a pattern with pattern synonym:"
        , Int -> SDoc -> SDoc
nest 2 (SDoc -> SDoc) -> SDoc -> SDoc
forall a b. (a -> b) -> a -> b
$ PatSyn -> SDoc
forall a. Outputable a => a -> SDoc
ppr PatSyn
ps SDoc -> SDoc -> SDoc
<+> SDoc
dcolon
                   SDoc -> SDoc -> SDoc
<+> PatSyn -> SDoc
pprPatSynType PatSyn
ps SDoc -> SDoc -> SDoc
<> SDoc
comma ]

{- Note [Skolem info for pattern synonyms]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
For pattern synonym SkolemInfo we have
   SigSkol (PatSynCtxt p) ty _
but the type 'ty' is not very helpful.  The full pattern-synonym type
has the provided and required pieces, which it is inconvenient to
record and display here. So we simply don't display the type at all,
contenting outselves with just the name of the pattern synonym, which
is fine.  We could do more, but it doesn't seem worth it.

Note [SigSkol SkolemInfo]
~~~~~~~~~~~~~~~~~~~~~~~~~
Suppose we (deeply) skolemise a type
   f :: forall a. a -> forall b. b -> a
Then we'll instantiate [a :-> a', b :-> b'], and with the instantiated
      a' -> b' -> a.
But when, in an error message, we report that "b is a rigid type
variable bound by the type signature for f", we want to show the foralls
in the right place.  So we proceed as follows:

* In SigSkol we record
    - the original signature forall a. a -> forall b. b -> a
    - the instantiation mapping [a :-> a', b :-> b']

* Then when tidying in TcMType.tidySkolemInfo, we first tidy a' to
  whatever it tidies to, say a''; and then we walk over the type
  replacing the binder a by the tidied version a'', to give
       forall a''. a'' -> forall b''. b'' -> a''
  We need to do this under function arrows, to match what deeplySkolemise
  does.

* Typically a'' will have a nice pretty name like "a", but the point is
  that the foral-bound variables of the signature we report line up with
  the instantiated skolems lying  around in other types.


************************************************************************
*                                                                      *
            CtOrigin
*                                                                      *
************************************************************************
-}

data CtOrigin
  = GivenOrigin SkolemInfo

  -- All the others are for *wanted* constraints
  | OccurrenceOf Name              -- Occurrence of an overloaded identifier
  | OccurrenceOfRecSel RdrName     -- Occurrence of a record selector
  | AppOrigin                      -- An application of some kind

  | SpecPragOrigin UserTypeCtxt    -- Specialisation pragma for
                                   -- function or instance

  | TypeEqOrigin { CtOrigin -> Type
uo_actual   :: TcType
                 , CtOrigin -> Type
uo_expected :: TcType
                 , CtOrigin -> Maybe SDoc
uo_thing    :: Maybe SDoc
                       -- ^ The thing that has type "actual"
                 , CtOrigin -> Bool
uo_visible  :: Bool
                       -- ^ Is at least one of the three elements above visible?
                       -- (Errors from the polymorphic subsumption check are considered
                       -- visible.) Only used for prioritizing error messages.
                 }

  | KindEqOrigin  -- See Note [Equalities with incompatible kinds] in TcCanonical.
      TcType (Maybe TcType)     -- A kind equality arising from unifying these two types
      CtOrigin                  -- originally arising from this
      (Maybe TypeOrKind)        -- the level of the eq this arises from

  | IPOccOrigin  HsIPName       -- Occurrence of an implicit parameter
  | OverLabelOrigin FastString  -- Occurrence of an overloaded label

  | LiteralOrigin (HsOverLit GhcRn)     -- Occurrence of a literal
  | NegateOrigin                        -- Occurrence of syntactic negation

  | ArithSeqOrigin (ArithSeqInfo GhcRn) -- [x..], [x..y] etc
  | AssocFamPatOrigin   -- When matching the patterns of an associated
                        -- family instance with that of its parent class
  | SectionOrigin
  | TupleOrigin         -- (..,..)
  | ExprSigOrigin       -- e :: ty
  | PatSigOrigin        -- p :: ty
  | PatOrigin           -- Instantiating a polytyped pattern at a constructor
  | ProvCtxtOrigin      -- The "provided" context of a pattern synonym signature
        (PatSynBind GhcRn GhcRn) -- Information about the pattern synonym, in
                                 -- particular the name and the right-hand side
  | RecordUpdOrigin
  | ViewPatOrigin

  | ScOrigin TypeSize   -- Typechecking superclasses of an instance declaration
                        -- If the instance head is C ty1 .. tyn
                        --    then TypeSize = sizeTypes [ty1, .., tyn]
                        -- See Note [Solving superclass constraints] in TcInstDcls

  | DerivClauseOrigin   -- Typechecking a deriving clause (as opposed to
                        -- standalone deriving).
  | DerivOriginDC DataCon Int Bool
      -- Checking constraints arising from this data con and field index. The
      -- Bool argument in DerivOriginDC and DerivOriginCoerce is True if
      -- standalong deriving (with a wildcard constraint) is being used. This
      -- is used to inform error messages on how to recommended fixes (e.g., if
      -- the argument is True, then don't recommend "use standalone deriving",
      -- but rather "fill in the wildcard constraint yourself").
      -- See Note [Inferring the instance context] in TcDerivInfer
  | DerivOriginCoerce Id Type Type Bool
                        -- DerivOriginCoerce id ty1 ty2: Trying to coerce class method `id` from
                        -- `ty1` to `ty2`.
  | StandAloneDerivOrigin -- Typechecking stand-alone deriving. Useful for
                          -- constraints coming from a wildcard constraint,
                          -- e.g., deriving instance _ => Eq (Foo a)
                          -- See Note [Inferring the instance context]
                          -- in TcDerivInfer
  | DefaultOrigin       -- Typechecking a default decl
  | DoOrigin            -- Arising from a do expression
  | DoPatOrigin (LPat GhcRn) -- Arising from a failable pattern in
                             -- a do expression
  | MCompOrigin         -- Arising from a monad comprehension
  | MCompPatOrigin (LPat GhcRn) -- Arising from a failable pattern in a
                                -- monad comprehension
  | IfOrigin            -- Arising from an if statement
  | ProcOrigin          -- Arising from a proc expression
  | AnnOrigin           -- An annotation

  | FunDepOrigin1       -- A functional dependency from combining
        PredType CtLoc      -- This constraint arising from ...
        PredType CtLoc      -- and this constraint arising from ...

  | FunDepOrigin2       -- A functional dependency from combining
        PredType CtOrigin   -- This constraint arising from ...
        PredType SrcSpan    -- and this top-level instance
        -- We only need a CtOrigin on the first, because the location
        -- is pinned on the entire error message

  | HoleOrigin
  | UnboundOccurrenceOf OccName
  | ListOrigin          -- An overloaded list
  | StaticOrigin        -- A static form
  | FailablePattern (LPat GhcTcId) -- A failable pattern in do-notation for the
                                   -- MonadFail Proposal (MFP). Obsolete when
                                   -- actual desugaring to MonadFail.fail is
                                   -- live.
  | Shouldn'tHappenOrigin String
                            -- the user should never see this one,
                            -- unless ImpredicativeTypes is on, where all
                            -- bets are off
  | InstProvidedOrigin Module ClsInst
        -- Skolem variable arose when we were testing if an instance
        -- is solvable or not.

-- | Flag to see whether we're type-checking terms or kind-checking types
data TypeOrKind = TypeLevel | KindLevel
  deriving TypeOrKind -> TypeOrKind -> Bool
(TypeOrKind -> TypeOrKind -> Bool)
-> (TypeOrKind -> TypeOrKind -> Bool) -> Eq TypeOrKind
forall a. (a -> a -> Bool) -> (a -> a -> Bool) -> Eq a
/= :: TypeOrKind -> TypeOrKind -> Bool
$c/= :: TypeOrKind -> TypeOrKind -> Bool
== :: TypeOrKind -> TypeOrKind -> Bool
$c== :: TypeOrKind -> TypeOrKind -> Bool
Eq

instance Outputable TypeOrKind where
  ppr :: TypeOrKind -> SDoc
ppr TypeLevel = FilePath -> SDoc
text "TypeLevel"
  ppr KindLevel = FilePath -> SDoc
text "KindLevel"

isTypeLevel :: TypeOrKind -> Bool
isTypeLevel :: TypeOrKind -> Bool
isTypeLevel TypeLevel = Bool
True
isTypeLevel KindLevel = Bool
False

isKindLevel :: TypeOrKind -> Bool
isKindLevel :: TypeOrKind -> Bool
isKindLevel TypeLevel = Bool
False
isKindLevel KindLevel = Bool
True

-- An origin is visible if the place where the constraint arises is manifest
-- in user code. Currently, all origins are visible except for invisible
-- TypeEqOrigins. This is used when choosing which error of
-- several to report
isVisibleOrigin :: CtOrigin -> Bool
isVisibleOrigin :: CtOrigin -> Bool
isVisibleOrigin (TypeEqOrigin { uo_visible :: CtOrigin -> Bool
uo_visible = Bool
vis }) = Bool
vis
isVisibleOrigin (KindEqOrigin _ _ sub_orig :: CtOrigin
sub_orig _)       = CtOrigin -> Bool
isVisibleOrigin CtOrigin
sub_orig
isVisibleOrigin _                                   = Bool
True

-- Converts a visible origin to an invisible one, if possible. Currently,
-- this works only for TypeEqOrigin
toInvisibleOrigin :: CtOrigin -> CtOrigin
toInvisibleOrigin :: CtOrigin -> CtOrigin
toInvisibleOrigin orig :: CtOrigin
orig@(TypeEqOrigin {}) = CtOrigin
orig { uo_visible :: Bool
uo_visible = Bool
False }
toInvisibleOrigin orig :: CtOrigin
orig                   = CtOrigin
orig

instance Outputable CtOrigin where
  ppr :: CtOrigin -> SDoc
ppr = CtOrigin -> SDoc
pprCtOrigin

ctoHerald :: SDoc
ctoHerald :: SDoc
ctoHerald = FilePath -> SDoc
text "arising from"

-- | Extract a suitable CtOrigin from a HsExpr
lexprCtOrigin :: LHsExpr GhcRn -> CtOrigin
lexprCtOrigin :: LHsExpr GhcRn -> CtOrigin
lexprCtOrigin (L _ e :: HsExpr GhcRn
e) = HsExpr GhcRn -> CtOrigin
exprCtOrigin HsExpr GhcRn
e

exprCtOrigin :: HsExpr GhcRn -> CtOrigin
exprCtOrigin :: HsExpr GhcRn -> CtOrigin
exprCtOrigin (HsVar _ (L _ name :: IdP GhcRn
name)) = Name -> CtOrigin
OccurrenceOf Name
IdP GhcRn
name
exprCtOrigin (HsUnboundVar _ uv :: UnboundVar
uv)  = OccName -> CtOrigin
UnboundOccurrenceOf (UnboundVar -> OccName
unboundVarOcc UnboundVar
uv)
exprCtOrigin (HsConLikeOut {})    = FilePath -> CtOrigin
forall a. FilePath -> a
panic "exprCtOrigin HsConLikeOut"
exprCtOrigin (HsRecFld _ f :: AmbiguousFieldOcc GhcRn
f)    = RdrName -> CtOrigin
OccurrenceOfRecSel (AmbiguousFieldOcc GhcRn -> RdrName
forall (p :: Pass). AmbiguousFieldOcc (GhcPass p) -> RdrName
rdrNameAmbiguousFieldOcc AmbiguousFieldOcc GhcRn
f)
exprCtOrigin (HsOverLabel _ _ l :: RuleName
l)  = RuleName -> CtOrigin
OverLabelOrigin RuleName
l
exprCtOrigin (HsIPVar _ ip :: HsIPName
ip)       = HsIPName -> CtOrigin
IPOccOrigin HsIPName
ip
exprCtOrigin (HsOverLit _ lit :: HsOverLit GhcRn
lit)    = HsOverLit GhcRn -> CtOrigin
LiteralOrigin HsOverLit GhcRn
lit
exprCtOrigin (HsLit {})           = FilePath -> CtOrigin
Shouldn'tHappenOrigin "concrete literal"
exprCtOrigin (HsLam _ matches :: MatchGroup GhcRn (LHsExpr GhcRn)
matches)    = MatchGroup GhcRn (LHsExpr GhcRn) -> CtOrigin
matchesCtOrigin MatchGroup GhcRn (LHsExpr GhcRn)
matches
exprCtOrigin (HsLamCase _ ms :: MatchGroup GhcRn (LHsExpr GhcRn)
ms)     = MatchGroup GhcRn (LHsExpr GhcRn) -> CtOrigin
matchesCtOrigin MatchGroup GhcRn (LHsExpr GhcRn)
ms
exprCtOrigin (HsApp _ e1 :: LHsExpr GhcRn
e1 _)       = LHsExpr GhcRn -> CtOrigin
lexprCtOrigin LHsExpr GhcRn
e1
exprCtOrigin (HsAppType _ e1 :: LHsExpr GhcRn
e1 _)   = LHsExpr GhcRn -> CtOrigin
lexprCtOrigin LHsExpr GhcRn
e1
exprCtOrigin (OpApp _ _ op :: LHsExpr GhcRn
op _)     = LHsExpr GhcRn -> CtOrigin
lexprCtOrigin LHsExpr GhcRn
op
exprCtOrigin (NegApp _ e :: LHsExpr GhcRn
e _)       = LHsExpr GhcRn -> CtOrigin
lexprCtOrigin LHsExpr GhcRn
e
exprCtOrigin (HsPar _ e :: LHsExpr GhcRn
e)          = LHsExpr GhcRn -> CtOrigin
lexprCtOrigin LHsExpr GhcRn
e
exprCtOrigin (SectionL _ _ _)     = CtOrigin
SectionOrigin
exprCtOrigin (SectionR _ _ _)     = CtOrigin
SectionOrigin
exprCtOrigin (ExplicitTuple {})   = FilePath -> CtOrigin
Shouldn'tHappenOrigin "explicit tuple"
exprCtOrigin ExplicitSum{}        = FilePath -> CtOrigin
Shouldn'tHappenOrigin "explicit sum"
exprCtOrigin (HsCase _ _ matches :: MatchGroup GhcRn (LHsExpr GhcRn)
matches) = MatchGroup GhcRn (LHsExpr GhcRn) -> CtOrigin
matchesCtOrigin MatchGroup GhcRn (LHsExpr GhcRn)
matches
exprCtOrigin (HsIf _ (Just syn :: SyntaxExpr GhcRn
syn) _ _ _) = HsExpr GhcRn -> CtOrigin
exprCtOrigin (SyntaxExpr GhcRn -> HsExpr GhcRn
forall p. SyntaxExpr p -> HsExpr p
syn_expr SyntaxExpr GhcRn
syn)
exprCtOrigin (HsIf {})           = FilePath -> CtOrigin
Shouldn'tHappenOrigin "if expression"
exprCtOrigin (HsMultiIf _ rhs :: [LGRHS GhcRn (LHsExpr GhcRn)]
rhs)   = [LGRHS GhcRn (LHsExpr GhcRn)] -> CtOrigin
lGRHSCtOrigin [LGRHS GhcRn (LHsExpr GhcRn)]
rhs
exprCtOrigin (HsLet _ _ e :: LHsExpr GhcRn
e)       = LHsExpr GhcRn -> CtOrigin
lexprCtOrigin LHsExpr GhcRn
e
exprCtOrigin (HsDo {})           = CtOrigin
DoOrigin
exprCtOrigin (ExplicitList {})   = FilePath -> CtOrigin
Shouldn'tHappenOrigin "list"
exprCtOrigin (RecordCon {})      = FilePath -> CtOrigin
Shouldn'tHappenOrigin "record construction"
exprCtOrigin (RecordUpd {})      = FilePath -> CtOrigin
Shouldn'tHappenOrigin "record update"
exprCtOrigin (ExprWithTySig {})  = CtOrigin
ExprSigOrigin
exprCtOrigin (ArithSeq {})       = FilePath -> CtOrigin
Shouldn'tHappenOrigin "arithmetic sequence"
exprCtOrigin (HsSCC _ _ _ e :: LHsExpr GhcRn
e)     = LHsExpr GhcRn -> CtOrigin
lexprCtOrigin LHsExpr GhcRn
e
exprCtOrigin (HsCoreAnn _ _ _ e :: LHsExpr GhcRn
e) = LHsExpr GhcRn -> CtOrigin
lexprCtOrigin LHsExpr GhcRn
e
exprCtOrigin (HsBracket {})      = FilePath -> CtOrigin
Shouldn'tHappenOrigin "TH bracket"
exprCtOrigin (HsRnBracketOut {})= FilePath -> CtOrigin
Shouldn'tHappenOrigin "HsRnBracketOut"
exprCtOrigin (HsTcBracketOut {})= FilePath -> CtOrigin
forall a. FilePath -> a
panic "exprCtOrigin HsTcBracketOut"
exprCtOrigin (HsSpliceE {})      = FilePath -> CtOrigin
Shouldn'tHappenOrigin "TH splice"
exprCtOrigin (HsProc {})         = FilePath -> CtOrigin
Shouldn'tHappenOrigin "proc"
exprCtOrigin (HsStatic {})       = FilePath -> CtOrigin
Shouldn'tHappenOrigin "static expression"
exprCtOrigin (HsArrApp {})       = FilePath -> CtOrigin
forall a. FilePath -> a
panic "exprCtOrigin HsArrApp"
exprCtOrigin (HsArrForm {})      = FilePath -> CtOrigin
forall a. FilePath -> a
panic "exprCtOrigin HsArrForm"
exprCtOrigin (HsTick _ _ e :: LHsExpr GhcRn
e)           = LHsExpr GhcRn -> CtOrigin
lexprCtOrigin LHsExpr GhcRn
e
exprCtOrigin (HsBinTick _ _ _ e :: LHsExpr GhcRn
e)      = LHsExpr GhcRn -> CtOrigin
lexprCtOrigin LHsExpr GhcRn
e
exprCtOrigin (HsTickPragma _ _ _ _ e :: LHsExpr GhcRn
e) = LHsExpr GhcRn -> CtOrigin
lexprCtOrigin LHsExpr GhcRn
e
exprCtOrigin (EWildPat {})      = FilePath -> CtOrigin
forall a. FilePath -> a
panic "exprCtOrigin EWildPat"
exprCtOrigin (EAsPat {})        = FilePath -> CtOrigin
forall a. FilePath -> a
panic "exprCtOrigin EAsPat"
exprCtOrigin (EViewPat {})      = FilePath -> CtOrigin
forall a. FilePath -> a
panic "exprCtOrigin EViewPat"
exprCtOrigin (ELazyPat {})      = FilePath -> CtOrigin
forall a. FilePath -> a
panic "exprCtOrigin ELazyPat"
exprCtOrigin (HsWrap {})        = FilePath -> CtOrigin
forall a. FilePath -> a
panic "exprCtOrigin HsWrap"
exprCtOrigin (XExpr {})         = FilePath -> CtOrigin
forall a. FilePath -> a
panic "exprCtOrigin XExpr"

-- | Extract a suitable CtOrigin from a MatchGroup
matchesCtOrigin :: MatchGroup GhcRn (LHsExpr GhcRn) -> CtOrigin
matchesCtOrigin :: MatchGroup GhcRn (LHsExpr GhcRn) -> CtOrigin
matchesCtOrigin (MG { mg_alts :: forall p body. MatchGroup p body -> Located [LMatch p body]
mg_alts = Located [LMatch GhcRn (LHsExpr GhcRn)]
alts })
  | L _ [L _ match :: Match GhcRn (LHsExpr GhcRn)
match] <- Located [LMatch GhcRn (LHsExpr GhcRn)]
alts
  , Match { m_grhss :: forall p body. Match p body -> GRHSs p body
m_grhss = GRHSs GhcRn (LHsExpr GhcRn)
grhss } <- Match GhcRn (LHsExpr GhcRn)
match
  = GRHSs GhcRn (LHsExpr GhcRn) -> CtOrigin
grhssCtOrigin GRHSs GhcRn (LHsExpr GhcRn)
grhss

  | Bool
otherwise
  = FilePath -> CtOrigin
Shouldn'tHappenOrigin "multi-way match"
matchesCtOrigin (XMatchGroup{}) = FilePath -> CtOrigin
forall a. FilePath -> a
panic "matchesCtOrigin"

-- | Extract a suitable CtOrigin from guarded RHSs
grhssCtOrigin :: GRHSs GhcRn (LHsExpr GhcRn) -> CtOrigin
grhssCtOrigin :: GRHSs GhcRn (LHsExpr GhcRn) -> CtOrigin
grhssCtOrigin (GRHSs { grhssGRHSs :: forall p body. GRHSs p body -> [LGRHS p body]
grhssGRHSs = [LGRHS GhcRn (LHsExpr GhcRn)]
lgrhss }) = [LGRHS GhcRn (LHsExpr GhcRn)] -> CtOrigin
lGRHSCtOrigin [LGRHS GhcRn (LHsExpr GhcRn)]
lgrhss
grhssCtOrigin (XGRHSs _) = FilePath -> CtOrigin
forall a. FilePath -> a
panic "grhssCtOrigin"

-- | Extract a suitable CtOrigin from a list of guarded RHSs
lGRHSCtOrigin :: [LGRHS GhcRn (LHsExpr GhcRn)] -> CtOrigin
lGRHSCtOrigin :: [LGRHS GhcRn (LHsExpr GhcRn)] -> CtOrigin
lGRHSCtOrigin [L _ (GRHS _ _ (L _ e :: HsExpr GhcRn
e))] = HsExpr GhcRn -> CtOrigin
exprCtOrigin HsExpr GhcRn
e
lGRHSCtOrigin [L _ (XGRHS _)] = FilePath -> CtOrigin
forall a. FilePath -> a
panic "lGRHSCtOrigin"
lGRHSCtOrigin _ = FilePath -> CtOrigin
Shouldn'tHappenOrigin "multi-way GRHS"

pprCtLoc :: CtLoc -> SDoc
-- "arising from ... at ..."
-- Not an instance of Outputable because of the "arising from" prefix
pprCtLoc :: CtLoc -> SDoc
pprCtLoc (CtLoc { ctl_origin :: CtLoc -> CtOrigin
ctl_origin = CtOrigin
o, ctl_env :: CtLoc -> TcLclEnv
ctl_env = TcLclEnv
lcl})
  = [SDoc] -> SDoc
sep [ CtOrigin -> SDoc
pprCtOrigin CtOrigin
o
        , FilePath -> SDoc
text "at" SDoc -> SDoc -> SDoc
<+> RealSrcSpan -> SDoc
forall a. Outputable a => a -> SDoc
ppr (TcLclEnv -> RealSrcSpan
tcl_loc TcLclEnv
lcl)]

pprCtOrigin :: CtOrigin -> SDoc
-- "arising from ..."
-- Not an instance of Outputable because of the "arising from" prefix
pprCtOrigin :: CtOrigin -> SDoc
pprCtOrigin (GivenOrigin sk :: SkolemInfo
sk) = SDoc
ctoHerald SDoc -> SDoc -> SDoc
<+> SkolemInfo -> SDoc
forall a. Outputable a => a -> SDoc
ppr SkolemInfo
sk

pprCtOrigin (SpecPragOrigin ctxt :: UserTypeCtxt
ctxt)
  = case UserTypeCtxt
ctxt of
       FunSigCtxt n :: Name
n _ -> FilePath -> SDoc
text "a SPECIALISE pragma for" SDoc -> SDoc -> SDoc
<+> SDoc -> SDoc
quotes (Name -> SDoc
forall a. Outputable a => a -> SDoc
ppr Name
n)
       SpecInstCtxt   -> FilePath -> SDoc
text "a SPECIALISE INSTANCE pragma"
       _              -> FilePath -> SDoc
text "a SPECIALISE pragma"  -- Never happens I think

pprCtOrigin (FunDepOrigin1 pred1 :: Type
pred1 loc1 :: CtLoc
loc1 pred2 :: Type
pred2 loc2 :: CtLoc
loc2)
  = SDoc -> Int -> SDoc -> SDoc
hang (SDoc
ctoHerald SDoc -> SDoc -> SDoc
<+> FilePath -> SDoc
text "a functional dependency between constraints:")
       2 ([SDoc] -> SDoc
vcat [ SDoc -> Int -> SDoc -> SDoc
hang (SDoc -> SDoc
quotes (Type -> SDoc
forall a. Outputable a => a -> SDoc
ppr Type
pred1)) 2 (CtLoc -> SDoc
pprCtLoc CtLoc
loc1)
               , SDoc -> Int -> SDoc -> SDoc
hang (SDoc -> SDoc
quotes (Type -> SDoc
forall a. Outputable a => a -> SDoc
ppr Type
pred2)) 2 (CtLoc -> SDoc
pprCtLoc CtLoc
loc2) ])

pprCtOrigin (FunDepOrigin2 pred1 :: Type
pred1 orig1 :: CtOrigin
orig1 pred2 :: Type
pred2 loc2 :: SrcSpan
loc2)
  = SDoc -> Int -> SDoc -> SDoc
hang (SDoc
ctoHerald SDoc -> SDoc -> SDoc
<+> FilePath -> SDoc
text "a functional dependency between:")
       2 ([SDoc] -> SDoc
vcat [ SDoc -> Int -> SDoc -> SDoc
hang (FilePath -> SDoc
text "constraint" SDoc -> SDoc -> SDoc
<+> SDoc -> SDoc
quotes (Type -> SDoc
forall a. Outputable a => a -> SDoc
ppr Type
pred1))
                    2 (CtOrigin -> SDoc
pprCtOrigin CtOrigin
orig1 )
               , SDoc -> Int -> SDoc -> SDoc
hang (FilePath -> SDoc
text "instance" SDoc -> SDoc -> SDoc
<+> SDoc -> SDoc
quotes (Type -> SDoc
forall a. Outputable a => a -> SDoc
ppr Type
pred2))
                    2 (FilePath -> SDoc
text "at" SDoc -> SDoc -> SDoc
<+> SrcSpan -> SDoc
forall a. Outputable a => a -> SDoc
ppr SrcSpan
loc2) ])

pprCtOrigin (KindEqOrigin t1 :: Type
t1 (Just t2 :: Type
t2) _ _)
  = SDoc -> Int -> SDoc -> SDoc
hang (SDoc
ctoHerald SDoc -> SDoc -> SDoc
<+> FilePath -> SDoc
text "a kind equality arising from")
       2 ([SDoc] -> SDoc
sep [Type -> SDoc
forall a. Outputable a => a -> SDoc
ppr Type
t1, Char -> SDoc
char '~', Type -> SDoc
forall a. Outputable a => a -> SDoc
ppr Type
t2])

pprCtOrigin AssocFamPatOrigin
  = FilePath -> SDoc
text "when matching a family LHS with its class instance head"

pprCtOrigin (KindEqOrigin t1 :: Type
t1 Nothing _ _)
  = SDoc -> Int -> SDoc -> SDoc
hang (SDoc
ctoHerald SDoc -> SDoc -> SDoc
<+> FilePath -> SDoc
text "a kind equality when matching")
       2 (Type -> SDoc
forall a. Outputable a => a -> SDoc
ppr Type
t1)

pprCtOrigin (UnboundOccurrenceOf name :: OccName
name)
  = SDoc
ctoHerald SDoc -> SDoc -> SDoc
<+> FilePath -> SDoc
text "an undeclared identifier" SDoc -> SDoc -> SDoc
<+> SDoc -> SDoc
quotes (OccName -> SDoc
forall a. Outputable a => a -> SDoc
ppr OccName
name)

pprCtOrigin (DerivOriginDC dc :: DataCon
dc n :: Int
n _)
  = SDoc -> Int -> SDoc -> SDoc
hang (SDoc
ctoHerald SDoc -> SDoc -> SDoc
<+> FilePath -> SDoc
text "the" SDoc -> SDoc -> SDoc
<+> Int -> SDoc
speakNth Int
n
          SDoc -> SDoc -> SDoc
<+> FilePath -> SDoc
text "field of" SDoc -> SDoc -> SDoc
<+> SDoc -> SDoc
quotes (DataCon -> SDoc
forall a. Outputable a => a -> SDoc
ppr DataCon
dc))
       2 (SDoc -> SDoc
parens (FilePath -> SDoc
text "type" SDoc -> SDoc -> SDoc
<+> SDoc -> SDoc
quotes (Type -> SDoc
forall a. Outputable a => a -> SDoc
ppr Type
ty)))
  where
    ty :: Type
ty = DataCon -> [Type]
dataConOrigArgTys DataCon
dc [Type] -> Int -> Type
forall a. [a] -> Int -> a
!! (Int
nInt -> Int -> Int
forall a. Num a => a -> a -> a
-1)

pprCtOrigin (DerivOriginCoerce meth :: TyVar
meth ty1 :: Type
ty1 ty2 :: Type
ty2 _)
  = SDoc -> Int -> SDoc -> SDoc
hang (SDoc
ctoHerald SDoc -> SDoc -> SDoc
<+> FilePath -> SDoc
text "the coercion of the method" SDoc -> SDoc -> SDoc
<+> SDoc -> SDoc
quotes (TyVar -> SDoc
forall a. Outputable a => a -> SDoc
ppr TyVar
meth))
       2 ([SDoc] -> SDoc
sep [ FilePath -> SDoc
text "from type" SDoc -> SDoc -> SDoc
<+> SDoc -> SDoc
quotes (Type -> SDoc
forall a. Outputable a => a -> SDoc
ppr Type
ty1)
              , Int -> SDoc -> SDoc
nest 2 (SDoc -> SDoc) -> SDoc -> SDoc
forall a b. (a -> b) -> a -> b
$ FilePath -> SDoc
text "to type" SDoc -> SDoc -> SDoc
<+> SDoc -> SDoc
quotes (Type -> SDoc
forall a. Outputable a => a -> SDoc
ppr Type
ty2) ])

pprCtOrigin (DoPatOrigin pat :: LPat GhcRn
pat)
    = SDoc
ctoHerald SDoc -> SDoc -> SDoc
<+> FilePath -> SDoc
text "a do statement"
      SDoc -> SDoc -> SDoc
$$
      FilePath -> SDoc
text "with the failable pattern" SDoc -> SDoc -> SDoc
<+> SDoc -> SDoc
quotes (LPat GhcRn -> SDoc
forall a. Outputable a => a -> SDoc
ppr LPat GhcRn
pat)

pprCtOrigin (MCompPatOrigin pat :: LPat GhcRn
pat)
    = SDoc
ctoHerald SDoc -> SDoc -> SDoc
<+> [SDoc] -> SDoc
hsep [ FilePath -> SDoc
text "the failable pattern"
           , SDoc -> SDoc
quotes (LPat GhcRn -> SDoc
forall a. Outputable a => a -> SDoc
ppr LPat GhcRn
pat)
           , FilePath -> SDoc
text "in a statement in a monad comprehension" ]
pprCtOrigin (FailablePattern pat :: LPat GhcTc
pat)
    = SDoc
ctoHerald SDoc -> SDoc -> SDoc
<+> FilePath -> SDoc
text "the failable pattern" SDoc -> SDoc -> SDoc
<+> SDoc -> SDoc
quotes (LPat GhcTc -> SDoc
forall a. Outputable a => a -> SDoc
ppr LPat GhcTc
pat)
      SDoc -> SDoc -> SDoc
$$
      FilePath -> SDoc
text "(this will become an error in a future GHC release)"

pprCtOrigin (Shouldn'tHappenOrigin note :: FilePath
note)
  = (DynFlags -> SDoc) -> SDoc
sdocWithDynFlags ((DynFlags -> SDoc) -> SDoc) -> (DynFlags -> SDoc) -> SDoc
forall a b. (a -> b) -> a -> b
$ \dflags :: DynFlags
dflags ->
    if Extension -> DynFlags -> Bool
xopt Extension
LangExt.ImpredicativeTypes DynFlags
dflags
    then FilePath -> SDoc
text "a situation created by impredicative types"
    else
    [SDoc] -> SDoc
vcat [ FilePath -> SDoc
text "<< This should not appear in error messages. If you see this"
         , FilePath -> SDoc
text "in an error message, please report a bug mentioning" SDoc -> SDoc -> SDoc
<+> SDoc -> SDoc
quotes (FilePath -> SDoc
text FilePath
note) SDoc -> SDoc -> SDoc
<+> FilePath -> SDoc
text "at"
         , FilePath -> SDoc
text "https://ghc.haskell.org/trac/ghc/wiki/ReportABug >>" ]

pprCtOrigin (ProvCtxtOrigin PSB{ psb_id :: forall idL idR. PatSynBind idL idR -> Located (IdP idL)
psb_id = (L _ name :: IdP GhcRn
name) })
  = SDoc -> Int -> SDoc -> SDoc
hang (SDoc
ctoHerald SDoc -> SDoc -> SDoc
<+> FilePath -> SDoc
text "the \"provided\" constraints claimed by")
       2 (FilePath -> SDoc
text "the signature of" SDoc -> SDoc -> SDoc
<+> SDoc -> SDoc
quotes (Name -> SDoc
forall a. Outputable a => a -> SDoc
ppr Name
IdP GhcRn
name))

pprCtOrigin (InstProvidedOrigin mod :: Module
mod cls_inst :: ClsInst
cls_inst)
  = [SDoc] -> SDoc
vcat [ FilePath -> SDoc
text "arising when attempting to show that"
         , ClsInst -> SDoc
forall a. Outputable a => a -> SDoc
ppr ClsInst
cls_inst
         , FilePath -> SDoc
text "is provided by" SDoc -> SDoc -> SDoc
<+> SDoc -> SDoc
quotes (Module -> SDoc
forall a. Outputable a => a -> SDoc
ppr Module
mod)]

pprCtOrigin simple_origin :: CtOrigin
simple_origin
  = SDoc
ctoHerald SDoc -> SDoc -> SDoc
<+> CtOrigin -> SDoc
pprCtO CtOrigin
simple_origin

-- | Short one-liners
pprCtO :: CtOrigin -> SDoc
pprCtO :: CtOrigin -> SDoc
pprCtO (OccurrenceOf name :: Name
name)   = [SDoc] -> SDoc
hsep [FilePath -> SDoc
text "a use of", SDoc -> SDoc
quotes (Name -> SDoc
forall a. Outputable a => a -> SDoc
ppr Name
name)]
pprCtO (OccurrenceOfRecSel name :: RdrName
name) = [SDoc] -> SDoc
hsep [FilePath -> SDoc
text "a use of", SDoc -> SDoc
quotes (RdrName -> SDoc
forall a. Outputable a => a -> SDoc
ppr RdrName
name)]
pprCtO AppOrigin             = FilePath -> SDoc
text "an application"
pprCtO (IPOccOrigin name :: HsIPName
name)    = [SDoc] -> SDoc
hsep [FilePath -> SDoc
text "a use of implicit parameter", SDoc -> SDoc
quotes (HsIPName -> SDoc
forall a. Outputable a => a -> SDoc
ppr HsIPName
name)]
pprCtO (OverLabelOrigin l :: RuleName
l)   = [SDoc] -> SDoc
hsep [FilePath -> SDoc
text "the overloaded label"
                                    ,SDoc -> SDoc
quotes (Char -> SDoc
char '#' SDoc -> SDoc -> SDoc
<> RuleName -> SDoc
forall a. Outputable a => a -> SDoc
ppr RuleName
l)]
pprCtO RecordUpdOrigin       = FilePath -> SDoc
text "a record update"
pprCtO ExprSigOrigin         = FilePath -> SDoc
text "an expression type signature"
pprCtO PatSigOrigin          = FilePath -> SDoc
text "a pattern type signature"
pprCtO PatOrigin             = FilePath -> SDoc
text "a pattern"
pprCtO ViewPatOrigin         = FilePath -> SDoc
text "a view pattern"
pprCtO IfOrigin              = FilePath -> SDoc
text "an if expression"
pprCtO (LiteralOrigin lit :: HsOverLit GhcRn
lit)   = [SDoc] -> SDoc
hsep [FilePath -> SDoc
text "the literal", SDoc -> SDoc
quotes (HsOverLit GhcRn -> SDoc
forall a. Outputable a => a -> SDoc
ppr HsOverLit GhcRn
lit)]
pprCtO (ArithSeqOrigin seq :: ArithSeqInfo GhcRn
seq)  = [SDoc] -> SDoc
hsep [FilePath -> SDoc
text "the arithmetic sequence", SDoc -> SDoc
quotes (ArithSeqInfo GhcRn -> SDoc
forall a. Outputable a => a -> SDoc
ppr ArithSeqInfo GhcRn
seq)]
pprCtO SectionOrigin         = FilePath -> SDoc
text "an operator section"
pprCtO AssocFamPatOrigin     = FilePath -> SDoc
text "the LHS of a famly instance"
pprCtO TupleOrigin           = FilePath -> SDoc
text "a tuple"
pprCtO NegateOrigin          = FilePath -> SDoc
text "a use of syntactic negation"
pprCtO (ScOrigin n :: IntWithInf
n)          = FilePath -> SDoc
text "the superclasses of an instance declaration"
                               SDoc -> SDoc -> SDoc
<> SDoc -> SDoc
whenPprDebug (SDoc -> SDoc
parens (IntWithInf -> SDoc
forall a. Outputable a => a -> SDoc
ppr IntWithInf
n))
pprCtO DerivClauseOrigin     = FilePath -> SDoc
text "the 'deriving' clause of a data type declaration"
pprCtO StandAloneDerivOrigin = FilePath -> SDoc
text "a 'deriving' declaration"
pprCtO DefaultOrigin         = FilePath -> SDoc
text "a 'default' declaration"
pprCtO DoOrigin              = FilePath -> SDoc
text "a do statement"
pprCtO MCompOrigin           = FilePath -> SDoc
text "a statement in a monad comprehension"
pprCtO ProcOrigin            = FilePath -> SDoc
text "a proc expression"
pprCtO (TypeEqOrigin t1 :: Type
t1 t2 :: Type
t2 _ _)= FilePath -> SDoc
text "a type equality" SDoc -> SDoc -> SDoc
<+> [SDoc] -> SDoc
sep [Type -> SDoc
forall a. Outputable a => a -> SDoc
ppr Type
t1, Char -> SDoc
char '~', Type -> SDoc
forall a. Outputable a => a -> SDoc
ppr Type
t2]
pprCtO AnnOrigin             = FilePath -> SDoc
text "an annotation"
pprCtO HoleOrigin            = FilePath -> SDoc
text "a use of" SDoc -> SDoc -> SDoc
<+> SDoc -> SDoc
quotes (FilePath -> SDoc
text "_")
pprCtO ListOrigin            = FilePath -> SDoc
text "an overloaded list"
pprCtO StaticOrigin          = FilePath -> SDoc
text "a static form"
pprCtO _                     = FilePath -> SDoc
forall a. FilePath -> a
panic "pprCtOrigin"

{-
Constraint Solver Plugins
-------------------------
-}

type TcPluginSolver = [Ct]    -- given
                   -> [Ct]    -- derived
                   -> [Ct]    -- wanted
                   -> TcPluginM TcPluginResult

newtype TcPluginM a = TcPluginM (EvBindsVar -> TcM a)

instance Functor TcPluginM where
  fmap :: (a -> b) -> TcPluginM a -> TcPluginM b
fmap = (a -> b) -> TcPluginM a -> TcPluginM b
forall (m :: * -> *) a1 r. Monad m => (a1 -> r) -> m a1 -> m r
liftM

instance Applicative TcPluginM where
  pure :: a -> TcPluginM a
pure x :: a
x = (EvBindsVar -> TcM a) -> TcPluginM a
forall a. (EvBindsVar -> TcM a) -> TcPluginM a
TcPluginM (TcM a -> EvBindsVar -> TcM a
forall a b. a -> b -> a
const (TcM a -> EvBindsVar -> TcM a) -> TcM a -> EvBindsVar -> TcM a
forall a b. (a -> b) -> a -> b
$ a -> TcM a
forall (f :: * -> *) a. Applicative f => a -> f a
pure a
x)
  <*> :: TcPluginM (a -> b) -> TcPluginM a -> TcPluginM b
(<*>) = TcPluginM (a -> b) -> TcPluginM a -> TcPluginM b
forall (m :: * -> *) a b. Monad m => m (a -> b) -> m a -> m b
ap

instance Monad TcPluginM where
#if !MIN_VERSION_base(4,13,0)
  fail = MonadFail.fail
#endif
  TcPluginM m :: EvBindsVar -> TcM a
m >>= :: TcPluginM a -> (a -> TcPluginM b) -> TcPluginM b
>>= k :: a -> TcPluginM b
k =
    (EvBindsVar -> TcM b) -> TcPluginM b
forall a. (EvBindsVar -> TcM a) -> TcPluginM a
TcPluginM (\ ev :: EvBindsVar
ev -> do a
a <- EvBindsVar -> TcM a
m EvBindsVar
ev
                          TcPluginM b -> EvBindsVar -> TcM b
forall a. TcPluginM a -> EvBindsVar -> TcM a
runTcPluginM (a -> TcPluginM b
k a
a) EvBindsVar
ev)

instance MonadFail.MonadFail TcPluginM where
  fail :: FilePath -> TcPluginM a
fail x :: FilePath
x   = (EvBindsVar -> TcM a) -> TcPluginM a
forall a. (EvBindsVar -> TcM a) -> TcPluginM a
TcPluginM (TcM a -> EvBindsVar -> TcM a
forall a b. a -> b -> a
const (TcM a -> EvBindsVar -> TcM a) -> TcM a -> EvBindsVar -> TcM a
forall a b. (a -> b) -> a -> b
$ FilePath -> TcM a
forall (m :: * -> *) a. MonadFail m => FilePath -> m a
fail FilePath
x)

runTcPluginM :: TcPluginM a -> EvBindsVar -> TcM a
runTcPluginM :: TcPluginM a -> EvBindsVar -> TcM a
runTcPluginM (TcPluginM m :: EvBindsVar -> TcM a
m) = EvBindsVar -> TcM a
m

-- | This function provides an escape for direct access to
-- the 'TcM` monad.  It should not be used lightly, and
-- the provided 'TcPluginM' API should be favoured instead.
unsafeTcPluginTcM :: TcM a -> TcPluginM a
unsafeTcPluginTcM :: TcM a -> TcPluginM a
unsafeTcPluginTcM = (EvBindsVar -> TcM a) -> TcPluginM a
forall a. (EvBindsVar -> TcM a) -> TcPluginM a
TcPluginM ((EvBindsVar -> TcM a) -> TcPluginM a)
-> (TcM a -> EvBindsVar -> TcM a) -> TcM a -> TcPluginM a
forall b c a. (b -> c) -> (a -> b) -> a -> c
. TcM a -> EvBindsVar -> TcM a
forall a b. a -> b -> a
const

-- | Access the 'EvBindsVar' carried by the 'TcPluginM' during
-- constraint solving.  Returns 'Nothing' if invoked during
-- 'tcPluginInit' or 'tcPluginStop'.
getEvBindsTcPluginM :: TcPluginM EvBindsVar
getEvBindsTcPluginM :: TcPluginM EvBindsVar
getEvBindsTcPluginM = (EvBindsVar -> TcM EvBindsVar) -> TcPluginM EvBindsVar
forall a. (EvBindsVar -> TcM a) -> TcPluginM a
TcPluginM EvBindsVar -> TcM EvBindsVar
forall (m :: * -> *) a. Monad m => a -> m a
return


data TcPlugin = forall s. TcPlugin
  { ()
tcPluginInit  :: TcPluginM s
    -- ^ Initialize plugin, when entering type-checker.

  , ()
tcPluginSolve :: s -> TcPluginSolver
    -- ^ Solve some constraints.
    -- TODO: WRITE MORE DETAILS ON HOW THIS WORKS.

  , ()
tcPluginStop  :: s -> TcPluginM ()
   -- ^ Clean up after the plugin, when exiting the type-checker.
  }

data TcPluginResult
  = TcPluginContradiction [Ct]
    -- ^ The plugin found a contradiction.
    -- The returned constraints are removed from the inert set,
    -- and recorded as insoluble.

  | TcPluginOk [(EvTerm,Ct)] [Ct]
    -- ^ The first field is for constraints that were solved.
    -- These are removed from the inert set,
    -- and the evidence for them is recorded.
    -- The second field contains new work, that should be processed by
    -- the constraint solver.

{- *********************************************************************
*                                                                      *
                        Role annotations
*                                                                      *
********************************************************************* -}

type RoleAnnotEnv = NameEnv (LRoleAnnotDecl GhcRn)

mkRoleAnnotEnv :: [LRoleAnnotDecl GhcRn] -> RoleAnnotEnv
mkRoleAnnotEnv :: [LRoleAnnotDecl GhcRn] -> RoleAnnotEnv
mkRoleAnnotEnv role_annot_decls :: [LRoleAnnotDecl GhcRn]
role_annot_decls
 = [(Name, LRoleAnnotDecl GhcRn)] -> RoleAnnotEnv
forall a. [(Name, a)] -> NameEnv a
mkNameEnv [ (Name
name, LRoleAnnotDecl GhcRn
ra_decl)
             | LRoleAnnotDecl GhcRn
ra_decl <- [LRoleAnnotDecl GhcRn]
role_annot_decls
             , let name :: IdP GhcRn
name = RoleAnnotDecl GhcRn -> IdP GhcRn
forall pass. RoleAnnotDecl pass -> IdP pass
roleAnnotDeclName (LRoleAnnotDecl GhcRn -> SrcSpanLess (LRoleAnnotDecl GhcRn)
forall a. HasSrcSpan a => a -> SrcSpanLess a
unLoc LRoleAnnotDecl GhcRn
ra_decl)
             , Bool -> Bool
not (Name -> Bool
isUnboundName Name
name) ]
       -- Some of the role annots will be unbound;
       -- we don't wish to include these

emptyRoleAnnotEnv :: RoleAnnotEnv
emptyRoleAnnotEnv :: RoleAnnotEnv
emptyRoleAnnotEnv = RoleAnnotEnv
forall elt. UniqFM elt
emptyNameEnv

lookupRoleAnnot :: RoleAnnotEnv -> Name -> Maybe (LRoleAnnotDecl GhcRn)
lookupRoleAnnot :: RoleAnnotEnv -> Name -> Maybe (LRoleAnnotDecl GhcRn)
lookupRoleAnnot = RoleAnnotEnv -> Name -> Maybe (LRoleAnnotDecl GhcRn)
forall a. NameEnv a -> Name -> Maybe a
lookupNameEnv

getRoleAnnots :: [Name] -> RoleAnnotEnv
              -> ([LRoleAnnotDecl GhcRn], RoleAnnotEnv)
getRoleAnnots :: [Name] -> RoleAnnotEnv -> ([LRoleAnnotDecl GhcRn], RoleAnnotEnv)
getRoleAnnots bndrs :: [Name]
bndrs role_env :: RoleAnnotEnv
role_env
  = ( (Name -> Maybe (LRoleAnnotDecl GhcRn))
-> [Name] -> [LRoleAnnotDecl GhcRn]
forall a b. (a -> Maybe b) -> [a] -> [b]
mapMaybe (RoleAnnotEnv -> Name -> Maybe (LRoleAnnotDecl GhcRn)
lookupRoleAnnot RoleAnnotEnv
role_env) [Name]
bndrs
    , RoleAnnotEnv -> [Name] -> RoleAnnotEnv
forall a. NameEnv a -> [Name] -> NameEnv a
delListFromNameEnv RoleAnnotEnv
role_env [Name]
bndrs )