{-# LANGUAGE DataKinds           #-}
{-# LANGUAGE FlexibleContexts    #-}
{-# LANGUAGE MonadComprehensions #-}
{-# LANGUAGE RankNTypes          #-}
{-# LANGUAGE ScopedTypeVariables #-}
{-# LANGUAGE TypeFamilies        #-}
{-# LANGUAGE ViewPatterns        #-}
{-# LANGUAGE RecursiveDo        #-}

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

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

-}

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

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

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

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

          -- tyvars
        zonkAndScopedSort,

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

        kindGeneralizeAll,

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

        -- Multiplicity
        tcMult,

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

        -- Error messages
        funAppCtxt, addTyConFlavCtxt,

        -- Utils
        tyLitFromLit, tyLitFromOverloadedLit,
   ) where

import GHC.Prelude hiding ( head, init, last, tail )

import GHC.Hs
import GHC.Rename.Utils
import GHC.Tc.Errors.Types
import GHC.Tc.Utils.Monad
import GHC.Tc.Types.Origin
import GHC.Tc.Types.LclEnv
import GHC.Tc.Types.Constraint
import GHC.Tc.Utils.Env
import GHC.Tc.Utils.TcMType
import GHC.Tc.Validity
import GHC.Tc.Utils.Unify
import GHC.IfaceToCore
import GHC.Tc.Solver
import GHC.Tc.Zonk.Type
import GHC.Tc.Utils.TcType
import GHC.Tc.Utils.Instantiate ( tcInstInvisibleTyBinders, tcInstInvisibleTyBindersN,
                                  tcInstInvisibleTyBinder, tcSkolemiseInvisibleBndrs,
                                  tcInstTypeBndrs )
import GHC.Tc.Zonk.TcType

import GHC.Core.Type
import GHC.Core.TyCo.Rep
import GHC.Core.TyCo.Ppr

import GHC.Builtin.Types.Prim
import GHC.Types.Error
import GHC.Types.Name.Env
import GHC.Types.Name.Reader( lookupLocalRdrOcc )
import GHC.Types.Var
import GHC.Types.Var.Set
import GHC.Core.TyCon
import GHC.Core.ConLike
import GHC.Core.DataCon
import GHC.Core.Class
import GHC.Types.Name
import GHC.Types.Var.Env
import GHC.Builtin.Types
import GHC.Types.Basic
import GHC.Types.SrcLoc
import GHC.Types.Unique
import GHC.Types.Unique.FM
import GHC.Utils.Misc
import GHC.Types.Unique.Supply
import GHC.Utils.Outputable
import GHC.Utils.Panic
import GHC.Builtin.Names hiding ( wildCardName )
import GHC.Driver.DynFlags
import qualified GHC.LanguageExtensions as LangExt

import GHC.Data.FastString
import GHC.Data.List.Infinite ( Infinite (..) )
import qualified GHC.Data.List.Infinite as Inf
import GHC.Data.List.SetOps
import GHC.Data.Maybe
import GHC.Data.Bag( unitBag )

import Data.Function ( on )
import Data.List.NonEmpty ( NonEmpty(..), nonEmpty )
import qualified Data.List.NonEmpty as NE
import Data.List ( mapAccumL )
import Control.Monad
import Data.Tuple( swap )
import GHC.Types.SourceText

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

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

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

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

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

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

- Ambiguity checks involve functional dependencies

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

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

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

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

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

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

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

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

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

       ; spec_tkvs <- zonkAndScopedSort spec_tkvs

       ; reportUnsolvedEqualities skol_info spec_tkvs tclvl wanted

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

       ; final_ty <- zonkTcTypeToType (mkInfForAllTys kvs ty1)

       ; checkValidType final_ty

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

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

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

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

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

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

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


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

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

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

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

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

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

There are three steps (look at kindGeneraliseSome):

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

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

3. quantifyTyVars quantifies the remaining type variables

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

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

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

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

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

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

-}

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

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

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

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

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

kcClassSigType :: [LocatedN Name] -> LHsSigType GhcRn -> TcM ()
-- This is a special form of tcClassSigType that is used during the
-- kind-checking phase to infer the kind of class variables. Cf. tc_lhs_sig_type.
-- Importantly, this does *not* kind-generalize. Consider
--   class SC f where
--     meth :: forall a (x :: f a). Proxy x -> ()
-- When instantiating Proxy with kappa, we must unify kappa := f a. But we're
-- still working out the kind of f, and thus f a will have a coercion in it.
-- Coercions may block unification (Note [Equalities with incompatible kinds] in
-- GHC.Tc.Solver.Equality, wrinkle (EIK2)) and so we fail to unify. If we try to
-- kind-generalize, we'll end up promoting kappa to the top level (because
-- kind-generalization is normally done right before adding a binding to the context),
-- and then we can't set kappa := f a, because a is local.
kcClassSigType :: [GenLocated SrcSpanAnnN Name] -> LHsSigType GhcRn -> TcM ()
kcClassSigType [GenLocated SrcSpanAnnN Name]
names
    sig_ty :: LHsSigType GhcRn
sig_ty@(L SrcSpanAnnA
_ (HsSig { sig_bndrs :: forall pass. HsSigType pass -> HsOuterSigTyVarBndrs pass
sig_bndrs = HsOuterSigTyVarBndrs GhcRn
hs_outer_bndrs, sig_body :: forall pass. HsSigType pass -> LHsType pass
sig_body = LHsType GhcRn
hs_ty }))
  = UserTypeCtxt
-> GenLocated SrcSpanAnnA (HsSigType GhcRn) -> TcM () -> TcM ()
forall hs_ty a.
Outputable hs_ty =>
UserTypeCtxt -> LocatedA hs_ty -> TcM a -> TcM a
addSigCtxt ([GenLocated SrcSpanAnnN Name] -> UserTypeCtxt
funsSigCtxt [GenLocated SrcSpanAnnN Name]
names) LHsSigType GhcRn
GenLocated SrcSpanAnnA (HsSigType GhcRn)
sig_ty (TcM () -> TcM ()) -> TcM () -> TcM ()
forall a b. (a -> b) -> a -> b
$
    do { _ <- HsOuterSigTyVarBndrs GhcRn
-> TcM Type -> TcM (HsOuterTyVarBndrs Specificity GhcTc, Type)
forall a.
HsOuterSigTyVarBndrs GhcRn
-> TcM a -> TcM (HsOuterTyVarBndrs Specificity GhcTc, a)
bindOuterSigTKBndrs_Tv HsOuterSigTyVarBndrs GhcRn
hs_outer_bndrs    (TcM Type -> TcM (HsOuterTyVarBndrs Specificity GhcTc, Type))
-> TcM Type -> TcM (HsOuterTyVarBndrs Specificity GhcTc, Type)
forall a b. (a -> b) -> a -> b
$
              LHsType GhcRn -> Type -> TcM Type
tcCheckLHsType LHsType GhcRn
hs_ty Type
liftedTypeKind
       ; return () }

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

tcHsSigType :: UserTypeCtxt -> LHsSigType GhcRn -> TcM Type
-- Does validity checking
-- See Note [Recipe for checking a signature]
tcHsSigType :: UserTypeCtxt -> LHsSigType GhcRn -> TcM Type
tcHsSigType UserTypeCtxt
ctxt LHsSigType GhcRn
sig_ty
  = UserTypeCtxt
-> GenLocated SrcSpanAnnA (HsSigType GhcRn) -> TcM Type -> TcM Type
forall hs_ty a.
Outputable hs_ty =>
UserTypeCtxt -> LocatedA hs_ty -> TcM a -> TcM a
addSigCtxt UserTypeCtxt
ctxt LHsSigType GhcRn
GenLocated SrcSpanAnnA (HsSigType GhcRn)
sig_ty (TcM Type -> TcM Type) -> TcM Type -> TcM Type
forall a b. (a -> b) -> a -> b
$
    do { String -> SDoc -> TcM ()
traceTc String
"tcHsSigType {" (GenLocated SrcSpanAnnA (HsSigType GhcRn) -> SDoc
forall a. Outputable a => a -> SDoc
ppr LHsSigType GhcRn
GenLocated SrcSpanAnnA (HsSigType GhcRn)
sig_ty)
       ; skol_info <- SkolemInfoAnon -> IOEnv (Env TcGblEnv TcLclEnv) SkolemInfo
forall (m :: * -> *). MonadIO m => SkolemInfoAnon -> m SkolemInfo
mkSkolemInfo SkolemInfoAnon
skol_info
          -- Generalise here: see Note [Kind generalisation]
       ; (implic, ty) <- tc_lhs_sig_type skol_info sig_ty  (expectedKindInCtxt ctxt)

       -- Float out constraints, failing fast if not possible
       -- See Note [Failure in local type signatures] in GHC.Tc.Solver
       ; traceTc "tcHsSigType 2" (ppr implic)
       ; simplifyAndEmitFlatConstraints (mkImplicWC (unitBag implic))

       ; ty <- liftZonkM $ zonkTcType ty
       ; checkValidType ctxt ty
       ; traceTc "end tcHsSigType }" (ppr ty)
       ; return ty }
  where
    skol_info :: SkolemInfoAnon
skol_info = UserTypeCtxt -> SkolemInfoAnon
SigTypeSkol UserTypeCtxt
ctxt

tc_lhs_sig_type :: SkolemInfo -> LHsSigType GhcRn
               -> ContextKind -> TcM (Implication, TcType)
-- Kind-checks/desugars an 'LHsSigType',
--   solve equalities,
--   and then kind-generalizes.
-- This will never emit constraints, as it uses solveEqualities internally.
-- No validity checking or zonking
-- Returns also an implication for the unsolved constraints
tc_lhs_sig_type :: SkolemInfo
-> LHsSigType GhcRn -> ContextKind -> TcM (Implication, Type)
tc_lhs_sig_type SkolemInfo
skol_info full_hs_ty :: LHsSigType GhcRn
full_hs_ty@(L SrcSpanAnnA
loc (HsSig { sig_bndrs :: forall pass. HsSigType pass -> HsOuterSigTyVarBndrs pass
sig_bndrs = HsOuterSigTyVarBndrs GhcRn
hs_outer_bndrs
                                                   , sig_body :: forall pass. HsSigType pass -> LHsType pass
sig_body = LHsType GhcRn
hs_ty })) ContextKind
ctxt_kind
  = SrcSpanAnnA -> TcM (Implication, Type) -> TcM (Implication, Type)
forall ann a. EpAnn ann -> TcRn a -> TcRn a
setSrcSpanA SrcSpanAnnA
loc (TcM (Implication, Type) -> TcM (Implication, Type))
-> TcM (Implication, Type) -> TcM (Implication, Type)
forall a b. (a -> b) -> a -> b
$
    do { (tc_lvl, wanted, (exp_kind, (outer_bndrs, ty)))
              <- String
-> TcM (Type, (HsOuterTyVarBndrs Specificity GhcTc, Type))
-> TcM
     (TcLevel, WantedConstraints,
      (Type, (HsOuterTyVarBndrs Specificity GhcTc, Type)))
forall a. String -> TcM a -> TcM (TcLevel, WantedConstraints, a)
pushLevelAndSolveEqualitiesX String
"tc_lhs_sig_type" (TcM (Type, (HsOuterTyVarBndrs Specificity GhcTc, Type))
 -> TcM
      (TcLevel, WantedConstraints,
       (Type, (HsOuterTyVarBndrs Specificity GhcTc, Type))))
-> TcM (Type, (HsOuterTyVarBndrs Specificity GhcTc, Type))
-> TcM
     (TcLevel, WantedConstraints,
      (Type, (HsOuterTyVarBndrs Specificity GhcTc, Type)))
forall a b. (a -> b) -> a -> b
$
                 -- See Note [Failure in local type signatures]
                 do { exp_kind <- ContextKind -> TcM Type
newExpectedKind ContextKind
ctxt_kind
                          -- See Note [Escaping kind in type signatures]
                    ; stuff <- tcOuterTKBndrs skol_info hs_outer_bndrs $
                               tcCheckLHsType hs_ty exp_kind
                    ; return (exp_kind, stuff) }

       -- Default any unconstrained variables free in the kind
       -- See Note [Escaping kind in type signatures]
       ; exp_kind_dvs <- candidateQTyVarsOfType exp_kind
       ; doNotQuantifyTyVars exp_kind_dvs (err_ctx exp_kind)

       ; traceTc "tc_lhs_sig_type" (ppr hs_outer_bndrs $$ ppr outer_bndrs)
       ; outer_bndrs <- scopedSortOuter outer_bndrs

       ; let outer_tv_bndrs :: [InvisTVBinder] = outerTyVarBndrs outer_bndrs
             ty1 = [VarBndr TcTyVar Specificity] -> Type -> Type
mkInvisForAllTys [VarBndr TcTyVar Specificity]
outer_tv_bndrs Type
ty
       ; kvs <- kindGeneralizeSome skol_info wanted ty1

       -- Build an implication for any as-yet-unsolved kind equalities
       -- See Note [Skolem escape in type signatures]
       ; implic <- buildTvImplication (getSkolemInfo skol_info) kvs tc_lvl wanted

       ; return (implic, mkInfForAllTys kvs ty1) }
  where
    err_ctx :: Type -> TidyEnv -> ZonkM (TidyEnv, UninferrableTyVarCtx)
err_ctx Type
exp_kind TidyEnv
tidy_env
      = do { (tidy_env2, exp_kind) <- TidyEnv -> Type -> ZonkM (TidyEnv, Type)
zonkTidyTcType TidyEnv
tidy_env Type
exp_kind
           ; return (tidy_env2, UninfTyCtx_Sig exp_kind full_hs_ty) }



{- Note [Escaping kind in type signatures]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Consider kind-checking the signature for `foo` (#19495, #24686):
  type family T (r :: RuntimeRep) :: TYPE r

  foo :: forall (r :: RuntimeRep). T r
  foo = ...

We kind-check the type with expected kind `TYPE delta` (see newExpectedKind),
where `delta :: RuntimeRep` is as-yet unknown. (We can't use `TYPE LiftedRep`
because we allow signatures like `foo :: Int#`.)

Suppose we are at level L currently.  We do this
  * pushLevelAndSolveEqualitiesX: moves to level L+1
  * newExpectedKind: allocates delta{L+1}. Note carefully that
    this call is /outside/ the tcOuterTKBndrs call.
  * tcOuterTKBndrs: pushes the level again to L+2, binds skolem r{L+2}
  * kind-check the body (T r) :: TYPE delta{L+1}

Then
* We can't unify delta{L+1} with r{L+2}.
  And rightly so: skolem would escape.

* If delta{L+1} is unified with some-kind{L}, that is fine.
  This can happen
      \(x::a) -> let y :: a; y = x in ...(x :: Int#)...
  Here (x :: a :: TYPE gamma) is in the environment when we check
  the signature y::a.  We unify delta := gamma, and all is well.

* If delta{L+1} is unconstrained, we /must not/ quantify over it!
  E.g. Consider f :: Any   where Any :: forall k. k
  We kind-check this with expected kind TYPE kappa. We get
      Any @(TYPE kappa) :: TYPE kappa
  We don't want to generalise to     forall k. Any @k
  because that is ill-kinded: the kind of the body of the forall,
  (Any @k :: k) mentions the bound variable k.

  Instead we want to default it to LiftedRep.

  An alternative would be to promote it, similar to the monomorphism
  restriction, but the MR is pretty confusing.  Defaulting seems better

How does that defaulting happen?  Well, since we /currently/ default
RuntimeRep variables during generalisation, it'll happen in
kindGeneralize. But in principle we might allow generalisation over
RuntimeRep variables in future.  Moreover, what if we had
   kappa{L+1} := F alpha{L+1}
where F :: Type -> RuntimeRep.   Now it's alpha that is free in the kind
and it /won't/ be defaulted.

So we use doNotQuantifyTyVars to either default the free vars of
exp_kind (if possible), or error (if not).

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

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

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

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

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

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

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

tcTopLHsType :: UserTypeCtxt -> LHsSigType GhcRn -> TcM Type
tcTopLHsType :: UserTypeCtxt -> LHsSigType GhcRn -> TcM Type
tcTopLHsType UserTypeCtxt
ctxt LHsSigType GhcRn
lsig_ty
  = TcM Type -> TcM Type
forall r. TcM r -> TcM r
checkNoErrs (TcM Type -> TcM Type) -> TcM Type -> TcM Type
forall a b. (a -> b) -> a -> b
$  -- Fail eagerly to avoid follow-on errors.  We are at
                   -- top level so these constraints will never be solved later.
    TypeOrKind -> UserTypeCtxt -> LHsSigType GhcRn -> TcM Type
tc_top_lhs_type TypeOrKind
TypeLevel UserTypeCtxt
ctxt LHsSigType GhcRn
lsig_ty

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

       ; outer_bndrs <- scopedSortOuter outer_bndrs
       ; let outer_tv_bndrs = HsOuterTyVarBndrs Specificity GhcTc
-> [VarBndr TcTyVar Specificity]
outerTyVarBndrs HsOuterTyVarBndrs Specificity GhcTc
outer_bndrs
             ty1 = [VarBndr TcTyVar Specificity] -> Type -> Type
mkInvisForAllTys [VarBndr TcTyVar Specificity]
outer_tv_bndrs Type
ty

       ; kvs <- kindGeneralizeAll skol_info ty1  -- "All" because it's a top-level type
       ; reportUnsolvedEqualities skol_info kvs tclvl wanted

       ; final_ty <- initZonkEnv DefaultFlexi
                   $ zonkTcTypeToTypeX (mkInfForAllTys kvs ty1)
       ; traceTc "tc_top_lhs_type }" (vcat [ppr sig_ty, ppr final_ty])
       ; return final_ty }
  where
    skol_info_anon :: SkolemInfoAnon
skol_info_anon = UserTypeCtxt -> SkolemInfoAnon
SigTypeSkol UserTypeCtxt
ctxt

tcClassConstraint :: Type -> TcM (Either (Maybe TyCon) ([TyVar], Class, [Type], [Kind]))
-- Like tcHsSigType, but for a simple class constraint of form ( C ty1 ty2 )
-- Returns the C, [ty1, ty2], and the kinds of C's remaining arguments
-- E.g.    class C (a::*) (b::k->k)
--         tcClassConstraint ( C Int ) returns Right ([k], C, [k, Int], [k->k])
-- Return values are fully zonked
tcClassConstraint :: Type
-> TcM (Either (Maybe TyCon) ([TcTyVar], Class, [Type], [Type]))
tcClassConstraint Type
ty
  = do { let ([TcTyVar]
tvs, Type
pred)    = Type -> ([TcTyVar], Type)
splitForAllTyCoVars Type
ty
             ([Scaled Type]
kind_args, Type
_) = Type -> ([Scaled Type], Type)
splitFunTys (HasDebugCallStack => Type -> Type
Type -> Type
typeKind Type
pred)
      -- Checking that `pred` a is type class application
       ; case HasDebugCallStack => Type -> Maybe (TyCon, [Type])
Type -> Maybe (TyCon, [Type])
splitTyConApp_maybe Type
pred of
          Just (TyCon
tyCon, [Type]
tyConArgs) ->
            case TyCon -> Maybe Class
tyConClass_maybe TyCon
tyCon of
              Just Class
clas ->
                Either (Maybe TyCon) ([TcTyVar], Class, [Type], [Type])
-> TcM (Either (Maybe TyCon) ([TcTyVar], Class, [Type], [Type]))
forall a. a -> IOEnv (Env TcGblEnv TcLclEnv) a
forall (m :: * -> *) a. Monad m => a -> m a
return (([TcTyVar], Class, [Type], [Type])
-> Either (Maybe TyCon) ([TcTyVar], Class, [Type], [Type])
forall a b. b -> Either a b
Right ([TcTyVar]
tvs, Class
clas, [Type]
tyConArgs, (Scaled Type -> Type) -> [Scaled Type] -> [Type]
forall a b. (a -> b) -> [a] -> [b]
map Scaled Type -> Type
forall a. Scaled a -> a
scaledThing [Scaled Type]
kind_args))
              Maybe Class
Nothing -> Either (Maybe TyCon) ([TcTyVar], Class, [Type], [Type])
-> TcM (Either (Maybe TyCon) ([TcTyVar], Class, [Type], [Type]))
forall a. a -> IOEnv (Env TcGblEnv TcLclEnv) a
forall (m :: * -> *) a. Monad m => a -> m a
return (Maybe TyCon
-> Either (Maybe TyCon) ([TcTyVar], Class, [Type], [Type])
forall a b. a -> Either a b
Left (TyCon -> Maybe TyCon
forall a. a -> Maybe a
Just TyCon
tyCon))
          Maybe (TyCon, [Type])
Nothing -> Either (Maybe TyCon) ([TcTyVar], Class, [Type], [Type])
-> TcM (Either (Maybe TyCon) ([TcTyVar], Class, [Type], [Type]))
forall a. a -> IOEnv (Env TcGblEnv TcLclEnv) a
forall (m :: * -> *) a. Monad m => a -> m a
return (Maybe TyCon
-> Either (Maybe TyCon) ([TcTyVar], Class, [Type], [Type])
forall a b. a -> Either a b
Left Maybe TyCon
forall a. Maybe a
Nothing) }

tcHsDefault :: LHsSigType GhcRn -> TcM ([TyVar], Class, [Type], [Kind])
-- Like tcHsSigType, but for the default ( C ty1 ty2 ) (ty1', ty2', ...) declaration
-- See Note [Named default declarations] in GHC.Tc.Gen.Default
tcHsDefault :: LHsSigType GhcRn -> TcM ([TcTyVar], Class, [Type], [Type])
tcHsDefault LHsSigType GhcRn
hs_ty
  = UserTypeCtxt -> LHsSigType GhcRn -> TcM Type
tcTopLHsType UserTypeCtxt
DefaultDeclCtxt LHsSigType GhcRn
hs_ty
    TcM Type
-> (Type
    -> TcM (Either (Maybe TyCon) ([TcTyVar], Class, [Type], [Type])))
-> TcM (Either (Maybe TyCon) ([TcTyVar], Class, [Type], [Type]))
forall a b.
IOEnv (Env TcGblEnv TcLclEnv) a
-> (a -> IOEnv (Env TcGblEnv TcLclEnv) b)
-> IOEnv (Env TcGblEnv TcLclEnv) b
forall (m :: * -> *) a b. Monad m => m a -> (a -> m b) -> m b
>>= Type
-> TcM (Either (Maybe TyCon) ([TcTyVar], Class, [Type], [Type]))
tcClassConstraint
    TcM (Either (Maybe TyCon) ([TcTyVar], Class, [Type], [Type]))
-> (Either (Maybe TyCon) ([TcTyVar], Class, [Type], [Type])
    -> TcM ([TcTyVar], Class, [Type], [Type]))
-> TcM ([TcTyVar], Class, [Type], [Type])
forall a b.
IOEnv (Env TcGblEnv TcLclEnv) a
-> (a -> IOEnv (Env TcGblEnv TcLclEnv) b)
-> IOEnv (Env TcGblEnv TcLclEnv) b
forall (m :: * -> *) a b. Monad m => m a -> (a -> m b) -> m b
>>= (Maybe TyCon -> TcM ([TcTyVar], Class, [Type], [Type]))
-> (([TcTyVar], Class, [Type], [Type])
    -> TcM ([TcTyVar], Class, [Type], [Type]))
-> Either (Maybe TyCon) ([TcTyVar], Class, [Type], [Type])
-> TcM ([TcTyVar], Class, [Type], [Type])
forall a c b. (a -> c) -> (b -> c) -> Either a b -> c
either (TcM ([TcTyVar], Class, [Type], [Type])
-> Maybe TyCon -> TcM ([TcTyVar], Class, [Type], [Type])
forall a b. a -> b -> a
const (TcM ([TcTyVar], Class, [Type], [Type])
 -> Maybe TyCon -> TcM ([TcTyVar], Class, [Type], [Type]))
-> TcM ([TcTyVar], Class, [Type], [Type])
-> Maybe TyCon
-> TcM ([TcTyVar], Class, [Type], [Type])
forall a b. (a -> b) -> a -> b
$ TcRnMessage -> TcM ([TcTyVar], Class, [Type], [Type])
forall a. TcRnMessage -> TcM a
failWithTc (TcRnMessage -> TcM ([TcTyVar], Class, [Type], [Type]))
-> TcRnMessage -> TcM ([TcTyVar], Class, [Type], [Type])
forall a b. (a -> b) -> a -> b
$ LHsSigType GhcRn -> TcRnMessage
TcRnIllegalDefaultClass LHsSigType GhcRn
hs_ty) ([TcTyVar], Class, [Type], [Type])
-> TcM ([TcTyVar], Class, [Type], [Type])
forall a. a -> IOEnv (Env TcGblEnv TcLclEnv) a
forall (m :: * -> *) a. Monad m => a -> m a
return

-----------------
tcHsDeriv :: LHsSigType GhcRn -> TcM ([TyVar], Class, [Type], [Kind])
-- Like tcHsSigType, but for the ...deriving( C ty1 ty2 ) clause
-- Returns the C, [ty1, ty2], and the kinds of C's remaining arguments
-- E.g.    class C (a::*) (b::k->k)
--         data T a b = ... deriving( C Int )
--    returns ([k], C, [k, Int], [k->k])
-- Return values are fully zonked
tcHsDeriv :: LHsSigType GhcRn -> TcM ([TcTyVar], Class, [Type], [Type])
tcHsDeriv LHsSigType GhcRn
hs_ty
  = do { ty <- UserTypeCtxt -> LHsSigType GhcRn -> TcM Type
tcTopLHsType UserTypeCtxt
DerivClauseCtxt LHsSigType GhcRn
hs_ty
       ; constrained <- tcClassConstraint ty
       ; case constrained of
           Left Maybe TyCon
Nothing -> TcRnMessage -> TcM ([TcTyVar], Class, [Type], [Type])
forall a. TcRnMessage -> TcM a
failWithTc (LHsSigType GhcRn -> TcRnMessage
TcRnIllegalDerivingItem LHsSigType GhcRn
hs_ty)
           Left (Just TyCon
tyCon) ->
             TcRnMessage -> TcM ([TcTyVar], Class, [Type], [Type])
forall a. TcRnMessage -> TcM a
failWithTc (TcRnMessage -> TcM ([TcTyVar], Class, [Type], [Type]))
-> TcRnMessage -> TcM ([TcTyVar], Class, [Type], [Type])
forall a b. (a -> b) -> a -> b
$ IllegalInstanceReason -> TcRnMessage
TcRnIllegalInstance
                        (IllegalInstanceReason -> TcRnMessage)
-> IllegalInstanceReason -> TcRnMessage
forall a b. (a -> b) -> a -> b
$ TypedThing -> IllegalClassInstanceReason -> IllegalInstanceReason
IllegalClassInstance (Type -> TypedThing
TypeThing Type
ty)
                        (IllegalClassInstanceReason -> IllegalInstanceReason)
-> IllegalClassInstanceReason -> IllegalInstanceReason
forall a b. (a -> b) -> a -> b
$ IllegalInstanceHeadReason -> IllegalClassInstanceReason
IllegalInstanceHead
                        (IllegalInstanceHeadReason -> IllegalClassInstanceReason)
-> IllegalInstanceHeadReason -> IllegalClassInstanceReason
forall a b. (a -> b) -> a -> b
$ Maybe TyCon -> IllegalInstanceHeadReason
InstHeadNonClass
                        (Maybe TyCon -> IllegalInstanceHeadReason)
-> Maybe TyCon -> IllegalInstanceHeadReason
forall a b. (a -> b) -> a -> b
$ TyCon -> Maybe TyCon
forall a. a -> Maybe a
Just TyCon
tyCon
           Right ([TcTyVar], Class, [Type], [Type])
result -> ([TcTyVar], Class, [Type], [Type])
-> TcM ([TcTyVar], Class, [Type], [Type])
forall a. a -> IOEnv (Env TcGblEnv TcLclEnv) a
forall (m :: * -> *) a. Monad m => a -> m a
return ([TcTyVar], Class, [Type], [Type])
result }

-- | Typecheck a deriving strategy. For most deriving strategies, this is a
-- no-op, but for the @via@ strategy, this requires typechecking the @via@ type.
tcDerivStrategy :: Maybe (LDerivStrategy GhcRn)
                   -- ^ The deriving strategy
                -> TcM (Maybe (LDerivStrategy GhcTc), [TcTyVar])
                   -- ^ The typechecked deriving strategy and the tyvars that it binds
                   -- (if using 'ViaStrategy').
tcDerivStrategy :: Maybe (LDerivStrategy GhcRn)
-> TcM (Maybe (LDerivStrategy GhcTc), [TcTyVar])
tcDerivStrategy Maybe (LDerivStrategy GhcRn)
mb_lds
  = case Maybe (LDerivStrategy GhcRn)
mb_lds of
      Maybe (LDerivStrategy GhcRn)
Nothing -> Maybe (GenLocated EpAnnCO (DerivStrategy GhcTc))
-> TcM
     (Maybe (GenLocated EpAnnCO (DerivStrategy GhcTc)), [TcTyVar])
forall ds a. ds -> TcM (ds, [a])
boring_case Maybe (GenLocated EpAnnCO (DerivStrategy GhcTc))
forall a. Maybe a
Nothing
      Just (L EpAnnCO
loc DerivStrategy GhcRn
ds) ->
        EpAnnCO
-> TcM (Maybe (LDerivStrategy GhcTc), [TcTyVar])
-> TcM (Maybe (LDerivStrategy GhcTc), [TcTyVar])
forall ann a. EpAnn ann -> TcRn a -> TcRn a
setSrcSpanA EpAnnCO
loc (TcM (Maybe (LDerivStrategy GhcTc), [TcTyVar])
 -> TcM (Maybe (LDerivStrategy GhcTc), [TcTyVar]))
-> TcM (Maybe (LDerivStrategy GhcTc), [TcTyVar])
-> TcM (Maybe (LDerivStrategy GhcTc), [TcTyVar])
forall a b. (a -> b) -> a -> b
$ do
          (ds', tvs) <- DerivStrategy GhcRn -> TcM (DerivStrategy GhcTc, [TcTyVar])
tc_deriv_strategy DerivStrategy GhcRn
ds
          pure (Just (L loc ds'), tvs)
  where
    tc_deriv_strategy :: DerivStrategy GhcRn
                      -> TcM (DerivStrategy GhcTc, [TyVar])
    tc_deriv_strategy :: DerivStrategy GhcRn -> TcM (DerivStrategy GhcTc, [TcTyVar])
tc_deriv_strategy (StockStrategy    XStockStrategy GhcRn
_) = DerivStrategy GhcTc -> TcM (DerivStrategy GhcTc, [TcTyVar])
forall ds a. ds -> TcM (ds, [a])
boring_case (XStockStrategy GhcTc -> DerivStrategy GhcTc
forall pass. XStockStrategy pass -> DerivStrategy pass
StockStrategy    XStockStrategy GhcTc
NoExtField
noExtField)
    tc_deriv_strategy (AnyclassStrategy XAnyClassStrategy GhcRn
_) = DerivStrategy GhcTc -> TcM (DerivStrategy GhcTc, [TcTyVar])
forall ds a. ds -> TcM (ds, [a])
boring_case (XAnyClassStrategy GhcTc -> DerivStrategy GhcTc
forall pass. XAnyClassStrategy pass -> DerivStrategy pass
AnyclassStrategy XAnyClassStrategy GhcTc
NoExtField
noExtField)
    tc_deriv_strategy (NewtypeStrategy  XNewtypeStrategy GhcRn
_) = DerivStrategy GhcTc -> TcM (DerivStrategy GhcTc, [TcTyVar])
forall ds a. ds -> TcM (ds, [a])
boring_case (XNewtypeStrategy GhcTc -> DerivStrategy GhcTc
forall pass. XNewtypeStrategy pass -> DerivStrategy pass
NewtypeStrategy  XNewtypeStrategy GhcTc
NoExtField
noExtField)
    tc_deriv_strategy (ViaStrategy XViaStrategy GhcRn
hs_sig)
      = do { ty <- UserTypeCtxt -> LHsSigType GhcRn -> TcM Type
tcTopLHsType UserTypeCtxt
DerivClauseCtxt XViaStrategy GhcRn
LHsSigType GhcRn
hs_sig
             -- rec {..}: see Note [Keeping SkolemInfo inside a SkolemTv]
             --           in GHC.Tc.Utils.TcType
           ; rec { (via_tvs, via_pred) <- tcSkolemiseInvisibleBndrs (DerivSkol via_pred) ty }
           ; pure (ViaStrategy via_pred, via_tvs) }

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

tcHsClsInstType :: UserTypeCtxt    -- InstDeclCtxt or SpecInstCtxt
                -> LHsSigType GhcRn
                -> TcM Type
-- Like tcHsSigType, but for a class instance declaration
tcHsClsInstType :: UserTypeCtxt -> LHsSigType GhcRn -> TcM Type
tcHsClsInstType UserTypeCtxt
user_ctxt LHsSigType GhcRn
hs_inst_ty
  = SrcSpan -> TcM Type -> TcM Type
forall a. SrcSpan -> TcRn a -> TcRn a
setSrcSpan (GenLocated SrcSpanAnnA (HsSigType GhcRn) -> SrcSpan
forall a e. HasLoc a => GenLocated a e -> SrcSpan
getLocA LHsSigType GhcRn
GenLocated SrcSpanAnnA (HsSigType GhcRn)
hs_inst_ty) (TcM Type -> TcM Type) -> TcM Type -> TcM Type
forall a b. (a -> b) -> a -> b
$
    do { inst_ty <- UserTypeCtxt -> LHsSigType GhcRn -> TcM Type
tcTopLHsType UserTypeCtxt
user_ctxt LHsSigType GhcRn
hs_inst_ty
       ; checkValidInstance user_ctxt hs_inst_ty inst_ty
       ; return inst_ty }

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

       -- We do not kind-generalize type applications: we just
       -- instantiate with exactly what the user says.
       -- See Note [No generalization in type application]
       -- We still must call kindGeneralizeNone, though, according
       -- to Note [Recipe for checking a signature]
       ; kindGeneralizeNone ty
       ; ty <- liftZonkM $ zonkTcType ty
       ; checkValidType TypeAppCtxt ty
       ; return ty }

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

Ugh!

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

  id @(Proxy Nothing)

If we kind-generalized, we would get

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

which is very sneakily impredicative instantiation.

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

-}

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

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

       -- Hack alert: see Note [tcFamTyPats: zonking the result kind]
       ; res_kind <- liftZonkM $ zonkTcType res_kind

       ; traceTc "End tcFamTyPats }" $
         vcat [ ppr fam_tc, text "res_kind:" <+> ppr res_kind ]

       ; return (fam_app, res_kind) }
  where
    fam_name :: Name
fam_name  = TyCon -> Name
tyConName TyCon
fam_tc
    fam_arity :: Int
fam_arity = TyCon -> Int
tyConArity TyCon
fam_tc
    lhs_fun :: GenLocated SrcSpanAnnA (HsType GhcRn)
lhs_fun   = HsType GhcRn -> GenLocated SrcSpanAnnA (HsType GhcRn)
forall e a. HasAnnotation e => a -> GenLocated e a
noLocA (XTyVar GhcRn -> PromotionFlag -> LIdP GhcRn -> HsType GhcRn
forall pass.
XTyVar pass -> PromotionFlag -> LIdP pass -> HsType pass
HsTyVar XTyVar GhcRn
forall a. NoAnn a => a
noAnn PromotionFlag
NotPromoted (Name -> GenLocated SrcSpanAnnN Name
forall e a. HasAnnotation e => a -> GenLocated e a
noLocA Name
fam_name))

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

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

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

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

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


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

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

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

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

tcInferLHsType :: LHsType GhcRn -> TcM TcType
tcInferLHsType :: LHsType GhcRn -> TcM Type
tcInferLHsType LHsType GhcRn
hs_ty
  = do { (ty,_kind) <- LHsType GhcRn -> TcM (Type, Type)
tcInferLHsTypeKind LHsType GhcRn
hs_ty
       ; return ty }

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

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

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

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

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

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

  x = id

then `id` gets instantiated to have type alpha -> alpha. The variable
alpha is then unconstrained and regeneralized. So we may well end up with
  x = /\x. id @a
But we cannot do this in types, as we have no type-level lambda.

So, we must be careful only to instantiate at the last possible moment, when
we're sure we're never going to want the lost polymorphism again. This is done
in calls to `tcInstInvisibleTyBinders`; a particular case in point is in
`checkExpectedKind`.

Otherwise, we are careful /not/ to instantiate.  For example:
* at a variable  in `tcTyVar`
* in `tcInferLHsTypeUnsaturated`, which is used by :kind in GHCi.

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

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

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

-}

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

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

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

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

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

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

mkHoleMode :: TypeOrKind -> HoleMode -> TcM TcTyMode
mkHoleMode :: TypeOrKind -> HoleMode -> TcM TcTyMode
mkHoleMode TypeOrKind
tyki HoleMode
hm
  = do { lvl <- TcM TcLevel
getTcLevel
       ; return (TcTyMode { mode_tyki  = tyki
                          , mode_holes = Just (lvl,hm) }) }

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

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

{-
Note [Bidirectional type checking]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
In types, as in terms, we use bidirectional type infefence.  The main workhorse
function looks like this:

    type ExpKind = ExpType
    data ExpType = Check TcSigmaKind | Infer ...(hole TcRhoType)...

    tcHsType :: TcTyMode -> HsType GhcRn -> ExpKind -> TcM TcType

* When the `ExpKind` argument is (Check ki), we /check/ that the type has
  kind `ki`
* When the `ExpKind` argument is (Infer hole), we /infer/ the kind of the
  type, and fill the hole with that kind
-}

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

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

tc_infer_hs_type :: TcTyMode -> HsType GhcRn -> TcM (Type, Type)
tc_infer_hs_type TcTyMode
mode HsType GhcRn
rn_ty
  = (ExpSigmaType -> TcM Type) -> TcM (Type, Type)
forall a. (ExpSigmaType -> TcM a) -> TcM (a, Type)
tcInfer ((ExpSigmaType -> TcM Type) -> TcM (Type, Type))
-> (ExpSigmaType -> TcM Type) -> TcM (Type, Type)
forall a b. (a -> b) -> a -> b
$ \ExpSigmaType
exp_kind -> TcTyMode -> HsType GhcRn -> ExpSigmaType -> TcM Type
tcHsType TcTyMode
mode HsType GhcRn
rn_ty ExpSigmaType
exp_kind

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

  newtype T a = MkT a deriving newtype Eq

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

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

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

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

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

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

------------------------------------------
tcCheckLHsType :: LHsType GhcRn -> TcKind -> TcM TcType
tcCheckLHsType :: LHsType GhcRn -> Type -> TcM Type
tcCheckLHsType LHsType GhcRn
hs_ty Type
exp_kind
  = TcTyMode -> LHsType GhcRn -> Type -> TcM Type
tc_check_lhs_type TcTyMode
typeLevelMode LHsType GhcRn
hs_ty Type
exp_kind

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

tc_check_hs_type :: TcTyMode -> HsType GhcRn -> TcKind -> TcM TcType
-- See Note [Bidirectional type checking]
tc_check_hs_type :: TcTyMode -> HsType GhcRn -> Type -> TcM Type
tc_check_hs_type TcTyMode
mode HsType GhcRn
ty Type
ek = TcTyMode -> HsType GhcRn -> ExpSigmaType -> TcM Type
tcHsType TcTyMode
mode HsType GhcRn
ty (Type -> ExpSigmaType
Check Type
ek)

tcLHsType :: TcTyMode -> LHsType GhcRn -> ExpKind -> TcM TcType
tcLHsType :: TcTyMode -> LHsType GhcRn -> ExpSigmaType -> TcM Type
tcLHsType TcTyMode
mode (L SrcSpanAnnA
span HsType GhcRn
ty) ExpSigmaType
exp_kind
  = SrcSpanAnnA -> TcM Type -> TcM Type
forall ann a. EpAnn ann -> TcRn a -> TcRn a
setSrcSpanA SrcSpanAnnA
span (TcM Type -> TcM Type) -> TcM Type -> TcM Type
forall a b. (a -> b) -> a -> b
$
    TcTyMode -> HsType GhcRn -> ExpSigmaType -> TcM Type
tcHsType TcTyMode
mode HsType GhcRn
ty ExpSigmaType
exp_kind

tcHsType :: TcTyMode -> HsType GhcRn -> ExpKind -> TcM TcType
-- The main workhorse for type kind checking
-- See Note [Bidirectional type checking]

tcHsType :: TcTyMode -> HsType GhcRn -> ExpSigmaType -> TcM Type
tcHsType TcTyMode
mode (HsParTy XParTy GhcRn
_ LHsType GhcRn
ty)   ExpSigmaType
exp_kind = TcTyMode -> LHsType GhcRn -> ExpSigmaType -> TcM Type
tcLHsType TcTyMode
mode LHsType GhcRn
ty ExpSigmaType
exp_kind
tcHsType TcTyMode
mode (HsDocTy XDocTy GhcRn
_ LHsType GhcRn
ty LHsDoc GhcRn
_) ExpSigmaType
exp_kind = TcTyMode -> LHsType GhcRn -> ExpSigmaType -> TcM Type
tcLHsType TcTyMode
mode LHsType GhcRn
ty ExpSigmaType
exp_kind
tcHsType TcTyMode
_ ty :: HsType GhcRn
ty@(HsBangTy XBangTy GhcRn
_ HsBang
bang LHsType GhcRn
_) ExpSigmaType
_
    -- While top-level bangs at this point are eliminated (eg !(Maybe Int)),
    -- other kinds of bangs are not (eg ((!Maybe) Int)). These kinds of
    -- bangs are invalid, so fail. (#7210, #14761)
    = TcRnMessage -> TcM Type
forall a. TcRnMessage -> TcM a
failWith (TcRnMessage -> TcM Type) -> TcRnMessage -> TcM Type
forall a b. (a -> b) -> a -> b
$ HsType GhcRn -> HsBang -> TcRnMessage
TcRnUnexpectedAnnotation HsType GhcRn
ty HsBang
bang
tcHsType TcTyMode
_ ty :: HsType GhcRn
ty@(HsRecTy {})      ExpSigmaType
_
      -- Record types (which only show up temporarily in constructor
      -- signatures) should have been removed by now
    = TcRnMessage -> TcM Type
forall a. TcRnMessage -> TcM a
failWithTc (TcRnMessage -> TcM Type) -> TcRnMessage -> TcM Type
forall a b. (a -> b) -> a -> b
$ Either (HsType GhcPs) (HsType GhcRn) -> TcRnMessage
TcRnIllegalRecordSyntax (HsType GhcRn -> Either (HsType GhcPs) (HsType GhcRn)
forall a b. b -> Either a b
Right HsType GhcRn
ty)

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

tcHsType TcTyMode
_ (HsSpliceTy (HsUntypedSpliceNested Name
n) HsUntypedSplice GhcRn
s) ExpSigmaType
_ = String -> SDoc -> TcM Type
forall a. HasCallStack => String -> SDoc -> a
pprPanic String
"tcHsType: invalid nested splice" (Bool -> Maybe Name -> HsUntypedSplice GhcRn -> SDoc
forall (p :: Pass).
OutputableBndrId p =>
Bool -> Maybe Name -> HsUntypedSplice (GhcPass p) -> SDoc
pprUntypedSplice Bool
True (Name -> Maybe Name
forall a. a -> Maybe a
Just Name
n) HsUntypedSplice GhcRn
s)

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

tcHsType TcTyMode
mode (HsOpTy XOpTy GhcRn
_ PromotionFlag
_ LHsType GhcRn
ty1 (L SrcSpanAnnN
_ Name
op) LHsType GhcRn
ty2) ExpSigmaType
exp_kind
  | Name
op Name -> Unique -> Bool
forall a. Uniquable a => a -> Unique -> Bool
`hasKey` Unique
unrestrictedFunTyConKey
  = TcTyMode
-> HsArrow GhcRn
-> LHsType GhcRn
-> LHsType GhcRn
-> ExpSigmaType
-> TcM Type
tc_fun_type TcTyMode
mode (XUnrestrictedArrow (GenLocated SrcSpanAnnA (HsType GhcRn)) GhcRn
-> HsArrowOf (GenLocated SrcSpanAnnA (HsType GhcRn)) GhcRn
forall mult pass.
XUnrestrictedArrow mult pass -> HsArrowOf mult pass
HsUnrestrictedArrow NoExtField
XUnrestrictedArrow (GenLocated SrcSpanAnnA (HsType GhcRn)) GhcRn
noExtField) LHsType GhcRn
ty1 LHsType GhcRn
ty2 ExpSigmaType
exp_kind

--------- Foralls
tcHsType TcTyMode
mode t :: HsType GhcRn
t@(HsForAllTy { hst_tele :: forall pass. HsType pass -> HsForAllTelescope pass
hst_tele = HsForAllTelescope GhcRn
tele, hst_body :: forall pass. HsType pass -> LHsType pass
hst_body = LHsType GhcRn
ty }) ExpSigmaType
exp_kind
  | HsForAllInvis{} <- HsForAllTelescope GhcRn
tele
  = HsForAllTelescope GhcRn
-> GenLocated SrcSpanAnnA (HsType GhcRn)
-> ExpSigmaType
-> TcM Type
tc_hs_forall_ty HsForAllTelescope GhcRn
tele LHsType GhcRn
GenLocated SrcSpanAnnA (HsType GhcRn)
ty ExpSigmaType
exp_kind
                 -- For an invisible forall, we allow the body to have
                 -- an arbitrary kind (hence exp_kind above).
                 -- See Note [Body kind of a HsForAllTy]

  | HsForAllVis{} <- HsForAllTelescope GhcRn
tele
  = do { ek <- TcM Type
newOpenTypeKind
       ; r <- tc_hs_forall_ty tele ty (Check ek)
       ; checkExpKind t r ek exp_kind }
                 -- For a visible forall, we require that the body is of kind TYPE r.
                 -- See Note [Body kind of a HsForAllTy]

  where
    tc_hs_forall_ty :: HsForAllTelescope GhcRn
-> GenLocated SrcSpanAnnA (HsType GhcRn)
-> ExpSigmaType
-> TcM Type
tc_hs_forall_ty HsForAllTelescope GhcRn
tele GenLocated SrcSpanAnnA (HsType GhcRn)
ty ExpSigmaType
ek
      = do { (tv_bndrs, ty') <- TcTyMode
-> HsForAllTelescope GhcRn
-> TcM Type
-> TcM ([TcTyVarBinder], Type)
forall a.
TcTyMode
-> HsForAllTelescope GhcRn -> TcM a -> TcM ([TcTyVarBinder], a)
tcTKTelescope TcTyMode
mode HsForAllTelescope GhcRn
tele (TcM Type -> TcM ([TcTyVarBinder], Type))
-> TcM Type -> TcM ([TcTyVarBinder], Type)
forall a b. (a -> b) -> a -> b
$
                                TcTyMode -> LHsType GhcRn -> ExpSigmaType -> TcM Type
tcLHsType TcTyMode
mode LHsType GhcRn
GenLocated SrcSpanAnnA (HsType GhcRn)
ty ExpSigmaType
ek
                 -- Pass on the mode from the type, to any wildcards
                 -- in kind signatures on the forall'd variables
                 -- e.g.      f :: _ -> Int -> forall (a :: _). blah

             -- Do not kind-generalise here!  See Note [Kind generalisation]
           ; return (mkForAllTys tv_bndrs ty') }

tcHsType TcTyMode
mode (HsQualTy { hst_ctxt :: forall pass. HsType pass -> LHsContext pass
hst_ctxt = LHsContext GhcRn
ctxt, hst_body :: forall pass. HsType pass -> LHsType pass
hst_body = LHsType GhcRn
rn_ty }) ExpSigmaType
exp_kind
  | [GenLocated SrcSpanAnnA (HsType GhcRn)] -> Bool
forall a. [a] -> Bool
forall (t :: * -> *) a. Foldable t => t a -> Bool
null (GenLocated SrcSpanAnnC [GenLocated SrcSpanAnnA (HsType GhcRn)]
-> [GenLocated SrcSpanAnnA (HsType GhcRn)]
forall l e. GenLocated l e -> e
unLoc LHsContext GhcRn
GenLocated SrcSpanAnnC [GenLocated SrcSpanAnnA (HsType GhcRn)]
ctxt)
  = TcTyMode -> LHsType GhcRn -> ExpSigmaType -> TcM Type
tcLHsType TcTyMode
mode LHsType GhcRn
rn_ty ExpSigmaType
exp_kind
    -- See Note [Body kind of a HsQualTy]
  | Check Type
kind <- ExpSigmaType
exp_kind, Type -> Bool
isConstraintLikeKind Type
kind
  = do { ctxt' <- TcTyMode -> LHsContext GhcRn -> TcM [Type]
tc_hs_context TcTyMode
mode LHsContext GhcRn
ctxt
      ; ty'   <- tc_check_lhs_type mode rn_ty constraintKind
      ; return (tcMkDFunPhiTy ctxt' ty') }

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

      ; ek <- newOpenTypeKind  -- The body kind (result of the function) can
                                -- be TYPE r, for any r, hence newOpenTypeKind
      ; ty' <- tc_check_lhs_type mode rn_ty ek
      ; let res_ty = [Type] -> Type -> Type
HasDebugCallStack => [Type] -> Type -> Type
tcMkPhiTy [Type]
ctxt' Type
ty'
      ; checkExpKind (unLoc rn_ty) res_ty
                      liftedTypeKind exp_kind }

--------- Lists, arrays, and tuples
tcHsType TcTyMode
mode rn_ty :: HsType GhcRn
rn_ty@(HsListTy XListTy GhcRn
_ LHsType GhcRn
elt_ty) ExpSigmaType
exp_kind
  = do { tau_ty <- TcTyMode -> LHsType GhcRn -> Type -> TcM Type
tc_check_lhs_type TcTyMode
mode LHsType GhcRn
elt_ty Type
liftedTypeKind
       ; checkWiredInTyCon listTyCon
       ; checkExpKind rn_ty (mkListTy tau_ty) liftedTypeKind exp_kind }

tcHsType TcTyMode
mode rn_ty :: HsType GhcRn
rn_ty@(HsTupleTy XTupleTy GhcRn
_ HsTupleSort
tup_sort [LHsType GhcRn]
tys) ExpSigmaType
exp_kind
  = do k <- ExpSigmaType -> TcM Type
expTypeToType ExpSigmaType
exp_kind
       tc_hs_tuple_ty rn_ty mode tup_sort tys k

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

--------- Promoted lists and tuples
tcHsType TcTyMode
mode rn_ty :: HsType GhcRn
rn_ty@(HsExplicitListTy XExplicitListTy GhcRn
_ PromotionFlag
_ [LHsType GhcRn]
tys) ExpSigmaType
exp_kind
  -- See Note [Kind-checking explicit lists]

  | [GenLocated SrcSpanAnnA (HsType GhcRn)] -> Bool
forall a. [a] -> Bool
forall (t :: * -> *) a. Foldable t => t a -> Bool
null [LHsType GhcRn]
[GenLocated SrcSpanAnnA (HsType GhcRn)]
tys
  = do let ty :: Type
ty = TyCon -> Type
mkTyConTy TyCon
promotedNilDataCon
       let kind :: Type
kind = [TcTyVar] -> Type -> Type
mkSpecForAllTys [TcTyVar
alphaTyVar] (Type -> Type) -> Type -> Type
forall a b. (a -> b) -> a -> b
$ Type -> Type
mkListTy Type
alphaTy
       HsType GhcRn -> Type -> Type -> ExpSigmaType -> TcM Type
checkExpKind HsType GhcRn
rn_ty Type
ty Type
kind ExpSigmaType
exp_kind

  | Bool
otherwise
  = do { tks <- (GenLocated SrcSpanAnnA (HsType GhcRn) -> TcM (Type, Type))
-> [GenLocated SrcSpanAnnA (HsType GhcRn)]
-> IOEnv (Env TcGblEnv TcLclEnv) [(Type, Type)]
forall (t :: * -> *) (m :: * -> *) a b.
(Traversable t, Monad m) =>
(a -> m b) -> t a -> m (t b)
forall (m :: * -> *) a b. Monad m => (a -> m b) -> [a] -> m [b]
mapM (TcTyMode -> LHsType GhcRn -> TcM (Type, Type)
tc_infer_lhs_type TcTyMode
mode) [LHsType GhcRn]
[GenLocated SrcSpanAnnA (HsType GhcRn)]
tys
       ; (taus', kind) <- unifyKinds tys tks
       ; let ty = ((Type -> Type -> Type) -> Type -> [Type] -> Type
forall a b. (a -> b -> b) -> b -> [a] -> b
forall (t :: * -> *) a b.
Foldable t =>
(a -> b -> b) -> b -> t a -> b
foldr (Type -> Type -> Type -> Type
mk_cons Type
kind) (Type -> Type
mk_nil Type
kind) [Type]
taus')
       ; checkExpKind rn_ty ty (mkListTy kind) exp_kind }
  where
    mk_cons :: Type -> Type -> Type -> Type
mk_cons Type
k Type
a Type
b = TyCon -> [Type] -> Type
mkTyConApp (DataCon -> TyCon
promoteDataCon DataCon
consDataCon) [Type
k, Type
a, Type
b]
    mk_nil :: Type -> Type
mk_nil  Type
k     = TyCon -> [Type] -> Type
mkTyConApp (DataCon -> TyCon
promoteDataCon DataCon
nilDataCon) [Type
k]

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

--------- Constraint types
tcHsType TcTyMode
mode rn_ty :: HsType GhcRn
rn_ty@(HsIParamTy XIParamTy GhcRn
_ (L EpAnnCO
_ HsIPName
n) LHsType GhcRn
ty) ExpSigmaType
exp_kind
  = do { Bool -> TcM ()
forall (m :: * -> *). (HasCallStack, Applicative m) => Bool -> m ()
massert (TypeOrKind -> Bool
isTypeLevel (TcTyMode -> TypeOrKind
mode_tyki TcTyMode
mode))
       ; ty' <- TcTyMode -> LHsType GhcRn -> Type -> TcM Type
tc_check_lhs_type TcTyMode
mode LHsType GhcRn
ty Type
liftedTypeKind
       ; let n' = FastString -> Type
mkStrLitTy (FastString -> Type) -> FastString -> Type
forall a b. (a -> b) -> a -> b
$ HsIPName -> FastString
hsIPNameFS HsIPName
n
       ; ipClass <- tcLookupClass ipClassName
       ; checkExpKind rn_ty (mkClassPred ipClass [n',ty'])
                           constraintKind exp_kind }

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

--------- Literals
tcHsType TcTyMode
_ rn_ty :: HsType GhcRn
rn_ty@(HsTyLit XTyLit GhcRn
_ (HsNumTy XNumTy GhcRn
_ Integer
n)) ExpSigmaType
exp_kind
  = do { TyCon -> TcM ()
checkWiredInTyCon TyCon
naturalTyCon
       ; HsType GhcRn -> Type -> Type -> ExpSigmaType -> TcM Type
checkExpKind HsType GhcRn
rn_ty (Integer -> Type
mkNumLitTy Integer
n) Type
naturalTy ExpSigmaType
exp_kind }

tcHsType TcTyMode
_ rn_ty :: HsType GhcRn
rn_ty@(HsTyLit XTyLit GhcRn
_ (HsStrTy XStrTy GhcRn
_ FastString
s)) ExpSigmaType
exp_kind
  = do { TyCon -> TcM ()
checkWiredInTyCon TyCon
typeSymbolKindCon
       ; HsType GhcRn -> Type -> Type -> ExpSigmaType -> TcM Type
checkExpKind HsType GhcRn
rn_ty (FastString -> Type
mkStrLitTy FastString
s) Type
typeSymbolKind ExpSigmaType
exp_kind }
tcHsType TcTyMode
_ rn_ty :: HsType GhcRn
rn_ty@(HsTyLit XTyLit GhcRn
_ (HsCharTy XCharTy GhcRn
_ Char
c)) ExpSigmaType
exp_kind
  = do { TyCon -> TcM ()
checkWiredInTyCon TyCon
charTyCon
       ; HsType GhcRn -> Type -> Type -> ExpSigmaType -> TcM Type
checkExpKind HsType GhcRn
rn_ty (Char -> Type
mkCharLitTy Char
c) Type
charTy ExpSigmaType
exp_kind }

--------- Wildcards

tcHsType TcTyMode
mode ty :: HsType GhcRn
ty@(HsWildCardTy XWildCardTy GhcRn
_) ExpSigmaType
ek
  = do k <- ExpSigmaType -> TcM Type
expTypeToType ExpSigmaType
ek
       tcAnonWildCardOcc NoExtraConstraint mode ty k

--------- Type applications
tcHsType TcTyMode
mode rn_ty :: HsType GhcRn
rn_ty@(HsTyVar{})     ExpSigmaType
exp_kind = TcTyMode -> HsType GhcRn -> ExpSigmaType -> TcM Type
tc_app_ty TcTyMode
mode HsType GhcRn
rn_ty ExpSigmaType
exp_kind
tcHsType TcTyMode
mode rn_ty :: HsType GhcRn
rn_ty@(HsAppTy{})     ExpSigmaType
exp_kind = TcTyMode -> HsType GhcRn -> ExpSigmaType -> TcM Type
tc_app_ty TcTyMode
mode HsType GhcRn
rn_ty ExpSigmaType
exp_kind
tcHsType TcTyMode
mode rn_ty :: HsType GhcRn
rn_ty@(HsAppKindTy{}) ExpSigmaType
exp_kind = TcTyMode -> HsType GhcRn -> ExpSigmaType -> TcM Type
tc_app_ty TcTyMode
mode HsType GhcRn
rn_ty ExpSigmaType
exp_kind
tcHsType TcTyMode
mode rn_ty :: HsType GhcRn
rn_ty@(HsOpTy{})      ExpSigmaType
exp_kind = TcTyMode -> HsType GhcRn -> ExpSigmaType -> TcM Type
tc_app_ty TcTyMode
mode HsType GhcRn
rn_ty ExpSigmaType
exp_kind

tcHsType TcTyMode
mode rn_ty :: HsType GhcRn
rn_ty@(HsKindSig XKindSig GhcRn
_ LHsType GhcRn
ty LHsType GhcRn
sig) ExpSigmaType
exp_kind
  = do { let mode' :: TcTyMode
mode' = TcTyMode
mode { mode_tyki = KindLevel }
       ; sig' <- TcTyMode -> UserTypeCtxt -> LHsType GhcRn -> TcM Type
tc_lhs_kind_sig TcTyMode
mode' UserTypeCtxt
KindSigCtxt LHsType GhcRn
sig
                 -- We must typecheck the kind signature, and solve all
                 -- its equalities etc; from this point on we may do
                 -- things like instantiate its foralls, so it needs
                 -- to be fully determined (#14904)
       ; traceTc "tcHsType:sig" (ppr ty $$ ppr sig')
       ; ty' <- tcAddKindSigPlaceholders sig $
                tc_check_lhs_type mode ty sig'
       ; checkExpKind rn_ty ty' sig' exp_kind }

-- See Note [Typechecking HsCoreTys]
tcHsType TcTyMode
_ rn_ty :: HsType GhcRn
rn_ty@(XHsType XXType GhcRn
ty) ExpSigmaType
exp_kind
  = do env <- TcRnIf TcGblEnv TcLclEnv TcLclEnv
forall gbl lcl. TcRnIf gbl lcl lcl
getLclEnv
       -- Raw uniques since we go from NameEnv to TvSubstEnv.
       let subst_prs :: [(Unique, TcTyVar)]
           subst_prs = [ (Name -> Unique
forall a. Uniquable a => a -> Unique
getUnique Name
nm, TcTyVar
tv)
                       | ATyVar Name
nm TcTyVar
tv <- NameEnv TcTyThing -> [TcTyThing]
forall a. NameEnv a -> [a]
nonDetNameEnvElts (TcLclEnv -> NameEnv TcTyThing
getLclEnvTypeEnv TcLclEnv
env) ]
           subst = InScopeSet -> TvSubstEnv -> Subst
mkTvSubst
                     ([TcTyVar] -> InScopeSet
mkInScopeSetList ([TcTyVar] -> InScopeSet) -> [TcTyVar] -> InScopeSet
forall a b. (a -> b) -> a -> b
$ ((Unique, TcTyVar) -> TcTyVar) -> [(Unique, TcTyVar)] -> [TcTyVar]
forall a b. (a -> b) -> [a] -> [b]
map (Unique, TcTyVar) -> TcTyVar
forall a b. (a, b) -> b
snd [(Unique, TcTyVar)]
subst_prs)
                     ([(Unique, Type)] -> TvSubstEnv
forall {k} elt (key :: k). [(Unique, elt)] -> UniqFM key elt
listToUFM_Directly ([(Unique, Type)] -> TvSubstEnv) -> [(Unique, Type)] -> TvSubstEnv
forall a b. (a -> b) -> a -> b
$ ((Unique, TcTyVar) -> (Unique, Type))
-> [(Unique, TcTyVar)] -> [(Unique, Type)]
forall a b. (a -> b) -> [a] -> [b]
map ((TcTyVar -> Type) -> (Unique, TcTyVar) -> (Unique, Type)
forall a b. (a -> b) -> (Unique, a) -> (Unique, b)
forall (f :: * -> *) a b. Functor f => (a -> b) -> f a -> f b
fmap TcTyVar -> Type
mkTyVarTy) [(Unique, TcTyVar)]
subst_prs)
           ty' = HasDebugCallStack => Subst -> Type -> Type
Subst -> Type -> Type
substTy Subst
subst XXType GhcRn
Type
ty
       checkExpKind rn_ty ty' (typeKind ty') exp_kind

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

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

       ; tys' <- sequence [ setSrcSpanA loc $
                            checkExpectedKind hs_ty ty kind arg_kind
                          | ((L loc hs_ty),ty,kind) <- zip3 hs_tys tys kinds ]

       ; finish_tuple rn_ty tup_sort tys' (map (const arg_kind) tys') exp_kind }
tc_hs_tuple_ty HsType GhcRn
rn_ty TcTyMode
mode HsTupleSort
HsUnboxedTuple [LHsType GhcRn]
tys Type
exp_kind =
    HsType GhcRn
-> TcTyMode -> TupleSort -> [LHsType GhcRn] -> Type -> TcM Type
tc_tuple HsType GhcRn
rn_ty TcTyMode
mode TupleSort
UnboxedTuple [LHsType GhcRn]
tys Type
exp_kind

{-
Note [Kind-checking explicit lists]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
In a type, suppose we have an application (F [t1,t2]),
where [t1,t2] is an explicit list, and
   F :: [ki] -> blah

Then we want to return the type
   F ((:) @ki t2 ((:) @ki t2 ([] @ki)))
where the argument list is instantiated to F's argument kind `ki`.

But what about (G []), where
   G :: (forall k. [k]) -> blah

Here we want to return (G []), with no instantiation at all.  But since we have
no lambda in types, we must be careful not to instantiate that `[]`, because we
can't re-generalise it.  Hence, when kind-checking an explicit list, we need a
special case for `[]`.

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

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

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

------------------------------------------
tc_mult :: TcTyMode -> HsArrow GhcRn -> TcM Mult
tc_mult :: TcTyMode -> HsArrow GhcRn -> TcM Type
tc_mult TcTyMode
mode HsArrow GhcRn
ty = TcTyMode -> LHsType GhcRn -> Type -> TcM Type
tc_check_lhs_type TcTyMode
mode (HsArrow GhcRn -> LHsType GhcRn
arrowToHsType HsArrow GhcRn
ty) Type
multiplicityTy
------------------------------------------
tc_fun_type :: TcTyMode -> HsArrow GhcRn -> LHsType GhcRn -> LHsType GhcRn -> ExpKind
            -> TcM TcType
tc_fun_type :: TcTyMode
-> HsArrow GhcRn
-> LHsType GhcRn
-> LHsType GhcRn
-> ExpSigmaType
-> TcM Type
tc_fun_type TcTyMode
mode HsArrow GhcRn
mult LHsType GhcRn
ty1 LHsType GhcRn
ty2 ExpSigmaType
exp_kind = case TcTyMode -> TypeOrKind
mode_tyki TcTyMode
mode of
  TypeOrKind
TypeLevel ->
    do { String -> SDoc -> TcM ()
traceTc String
"tc_fun_type" (GenLocated SrcSpanAnnA (HsType GhcRn) -> SDoc
forall a. Outputable a => a -> SDoc
ppr LHsType GhcRn
GenLocated SrcSpanAnnA (HsType GhcRn)
ty1 SDoc -> SDoc -> SDoc
forall doc. IsDoc doc => doc -> doc -> doc
$$ GenLocated SrcSpanAnnA (HsType GhcRn) -> SDoc
forall a. Outputable a => a -> SDoc
ppr LHsType GhcRn
GenLocated SrcSpanAnnA (HsType GhcRn)
ty2)
       ; arg_k <- TcM Type
newOpenTypeKind
       ; res_k <- newOpenTypeKind
       ; ty1'  <- tc_check_lhs_type mode ty1 arg_k
       ; ty2'  <- tc_check_lhs_type mode ty2 res_k
       ; mult' <- tc_mult mode mult
       ; checkExpKind (HsFunTy noExtField mult ty1 ty2)
                      (tcMkVisFunTy mult' ty1' ty2')
                      liftedTypeKind exp_kind }
  TypeOrKind
KindLevel ->  -- no representation polymorphism in kinds. yet.
    do { ty1'  <- TcTyMode -> LHsType GhcRn -> Type -> TcM Type
tc_check_lhs_type TcTyMode
mode LHsType GhcRn
ty1 Type
liftedTypeKind
       ; ty2'  <- tc_check_lhs_type mode ty2 liftedTypeKind
       ; mult' <- tc_mult mode mult
       ; checkExpKind (HsFunTy noExtField mult ty1 ty2)
                      (tcMkVisFunTy mult' ty1' ty2')
                      liftedTypeKind exp_kind }

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

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

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

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

Note that

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

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

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

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

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

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

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

  data Solo a = Solo a

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

  class a => Solo% a

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

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

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

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

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

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

splitHsAppTys :: HsType GhcRn -> (LHsType GhcRn, [LHsTypeArg GhcRn])

splitHsAppTys :: HsType GhcRn -> (LHsType GhcRn, HsFamEqnPats GhcRn)
splitHsAppTys HsType GhcRn
hs_ty = LHsType GhcRn
-> HsFamEqnPats GhcRn -> (LHsType GhcRn, HsFamEqnPats GhcRn)
go (HsType GhcRn -> GenLocated SrcSpanAnnA (HsType GhcRn)
forall e a. HasAnnotation e => a -> GenLocated e a
noLocA HsType GhcRn
hs_ty) []
  where
    go :: LHsType GhcRn
       -> [HsArg GhcRn (LHsType GhcRn) (LHsKind GhcRn)]
       -> (LHsType GhcRn,
           [HsArg GhcRn (LHsType GhcRn) (LHsKind GhcRn)]) -- AZ temp
    go :: LHsType GhcRn
-> HsFamEqnPats GhcRn -> (LHsType GhcRn, HsFamEqnPats GhcRn)
go (L SrcSpanAnnA
_  (HsAppTy XAppTy GhcRn
_ LHsType GhcRn
f LHsType GhcRn
a))      HsFamEqnPats GhcRn
as = LHsType GhcRn
-> HsFamEqnPats GhcRn -> (LHsType GhcRn, HsFamEqnPats GhcRn)
go LHsType GhcRn
f (XValArg GhcRn
-> GenLocated SrcSpanAnnA (HsType GhcRn)
-> HsArg
     GhcRn
     (GenLocated SrcSpanAnnA (HsType GhcRn))
     (GenLocated SrcSpanAnnA (HsType GhcRn))
forall p tm ty. XValArg p -> tm -> HsArg p tm ty
HsValArg NoExtField
XValArg GhcRn
noExtField LHsType GhcRn
GenLocated SrcSpanAnnA (HsType GhcRn)
a HsArg
  GhcRn
  (GenLocated SrcSpanAnnA (HsType GhcRn))
  (GenLocated SrcSpanAnnA (HsType GhcRn))
-> [HsArg
      GhcRn
      (GenLocated SrcSpanAnnA (HsType GhcRn))
      (GenLocated SrcSpanAnnA (HsType GhcRn))]
-> [HsArg
      GhcRn
      (GenLocated SrcSpanAnnA (HsType GhcRn))
      (GenLocated SrcSpanAnnA (HsType GhcRn))]
forall a. a -> [a] -> [a]
: HsFamEqnPats GhcRn
[HsArg
   GhcRn
   (GenLocated SrcSpanAnnA (HsType GhcRn))
   (GenLocated SrcSpanAnnA (HsType GhcRn))]
as)
    go (L SrcSpanAnnA
_  (HsAppKindTy XAppKindTy GhcRn
_ LHsType GhcRn
ty LHsType GhcRn
k)) HsFamEqnPats GhcRn
as = LHsType GhcRn
-> HsFamEqnPats GhcRn -> (LHsType GhcRn, HsFamEqnPats GhcRn)
go LHsType GhcRn
ty (XTypeArg GhcRn
-> GenLocated SrcSpanAnnA (HsType GhcRn)
-> HsArg
     GhcRn
     (GenLocated SrcSpanAnnA (HsType GhcRn))
     (GenLocated SrcSpanAnnA (HsType GhcRn))
forall p tm ty. XTypeArg p -> ty -> HsArg p tm ty
HsTypeArg NoExtField
XTypeArg GhcRn
noExtField LHsType GhcRn
GenLocated SrcSpanAnnA (HsType GhcRn)
k HsArg
  GhcRn
  (GenLocated SrcSpanAnnA (HsType GhcRn))
  (GenLocated SrcSpanAnnA (HsType GhcRn))
-> [HsArg
      GhcRn
      (GenLocated SrcSpanAnnA (HsType GhcRn))
      (GenLocated SrcSpanAnnA (HsType GhcRn))]
-> [HsArg
      GhcRn
      (GenLocated SrcSpanAnnA (HsType GhcRn))
      (GenLocated SrcSpanAnnA (HsType GhcRn))]
forall a. a -> [a] -> [a]
: HsFamEqnPats GhcRn
[HsArg
   GhcRn
   (GenLocated SrcSpanAnnA (HsType GhcRn))
   (GenLocated SrcSpanAnnA (HsType GhcRn))]
as)
    go (L SrcSpanAnnA
sp (HsParTy XParTy GhcRn
_ LHsType GhcRn
f))        HsFamEqnPats GhcRn
as = LHsType GhcRn
-> HsFamEqnPats GhcRn -> (LHsType GhcRn, HsFamEqnPats GhcRn)
go LHsType GhcRn
f (XArgPar GhcRn
-> HsArg
     GhcRn
     (GenLocated SrcSpanAnnA (HsType GhcRn))
     (GenLocated SrcSpanAnnA (HsType GhcRn))
forall p tm ty. XArgPar p -> HsArg p tm ty
HsArgPar (SrcSpanAnnA -> SrcSpan
forall a. HasLoc a => a -> SrcSpan
locA SrcSpanAnnA
sp) HsArg
  GhcRn
  (GenLocated SrcSpanAnnA (HsType GhcRn))
  (GenLocated SrcSpanAnnA (HsType GhcRn))
-> [HsArg
      GhcRn
      (GenLocated SrcSpanAnnA (HsType GhcRn))
      (GenLocated SrcSpanAnnA (HsType GhcRn))]
-> [HsArg
      GhcRn
      (GenLocated SrcSpanAnnA (HsType GhcRn))
      (GenLocated SrcSpanAnnA (HsType GhcRn))]
forall a. a -> [a] -> [a]
: HsFamEqnPats GhcRn
[HsArg
   GhcRn
   (GenLocated SrcSpanAnnA (HsType GhcRn))
   (GenLocated SrcSpanAnnA (HsType GhcRn))]
as)
    go (L SrcSpanAnnA
_  (HsOpTy XOpTy GhcRn
_ PromotionFlag
prom LHsType GhcRn
l op :: LIdP GhcRn
op@(L SrcSpanAnnN
sp Name
_) LHsType GhcRn
r)) HsFamEqnPats GhcRn
as
      = ( SrcSpanAnnA
-> HsType GhcRn -> GenLocated SrcSpanAnnA (HsType GhcRn)
forall l e. l -> e -> GenLocated l e
L (SrcSpanAnnN -> SrcSpanAnnA
forall a b. (HasLoc a, HasAnnotation b) => a -> b
l2l SrcSpanAnnN
sp) (XTyVar GhcRn -> PromotionFlag -> LIdP GhcRn -> HsType GhcRn
forall pass.
XTyVar pass -> PromotionFlag -> LIdP pass -> HsType pass
HsTyVar [AddEpAnn]
XTyVar GhcRn
forall a. NoAnn a => a
noAnn PromotionFlag
prom LIdP GhcRn
op)
        , XValArg GhcRn
-> GenLocated SrcSpanAnnA (HsType GhcRn)
-> HsArg
     GhcRn
     (GenLocated SrcSpanAnnA (HsType GhcRn))
     (GenLocated SrcSpanAnnA (HsType GhcRn))
forall p tm ty. XValArg p -> tm -> HsArg p tm ty
HsValArg NoExtField
XValArg GhcRn
noExtField LHsType GhcRn
GenLocated SrcSpanAnnA (HsType GhcRn)
l HsArg
  GhcRn
  (GenLocated SrcSpanAnnA (HsType GhcRn))
  (GenLocated SrcSpanAnnA (HsType GhcRn))
-> [HsArg
      GhcRn
      (GenLocated SrcSpanAnnA (HsType GhcRn))
      (GenLocated SrcSpanAnnA (HsType GhcRn))]
-> [HsArg
      GhcRn
      (GenLocated SrcSpanAnnA (HsType GhcRn))
      (GenLocated SrcSpanAnnA (HsType GhcRn))]
forall a. a -> [a] -> [a]
: XValArg GhcRn
-> GenLocated SrcSpanAnnA (HsType GhcRn)
-> HsArg
     GhcRn
     (GenLocated SrcSpanAnnA (HsType GhcRn))
     (GenLocated SrcSpanAnnA (HsType GhcRn))
forall p tm ty. XValArg p -> tm -> HsArg p tm ty
HsValArg NoExtField
XValArg GhcRn
noExtField LHsType GhcRn
GenLocated SrcSpanAnnA (HsType GhcRn)
r HsArg
  GhcRn
  (GenLocated SrcSpanAnnA (HsType GhcRn))
  (GenLocated SrcSpanAnnA (HsType GhcRn))
-> [HsArg
      GhcRn
      (GenLocated SrcSpanAnnA (HsType GhcRn))
      (GenLocated SrcSpanAnnA (HsType GhcRn))]
-> [HsArg
      GhcRn
      (GenLocated SrcSpanAnnA (HsType GhcRn))
      (GenLocated SrcSpanAnnA (HsType GhcRn))]
forall a. a -> [a] -> [a]
: HsFamEqnPats GhcRn
[HsArg
   GhcRn
   (GenLocated SrcSpanAnnA (HsType GhcRn))
   (GenLocated SrcSpanAnnA (HsType GhcRn))]
as )
    go LHsType GhcRn
f HsFamEqnPats GhcRn
as = (LHsType GhcRn
f, HsFamEqnPats GhcRn
as)

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

tc_app_ty :: TcTyMode -> HsType GhcRn -> ExpKind -> TcM TcType
tc_app_ty :: TcTyMode -> HsType GhcRn -> ExpSigmaType -> TcM Type
tc_app_ty TcTyMode
mode HsType GhcRn
rn_ty ExpSigmaType
exp_kind
  = do { (fun_ty, _ki) <- TcTyMode -> LHsType GhcRn -> TcM (Type, Type)
tcInferTyAppHead TcTyMode
mode LHsType GhcRn
hs_fun_ty
       ; (ty, infered_kind) <- tcInferTyApps mode hs_fun_ty fun_ty hs_args
       ; checkExpKind rn_ty ty infered_kind exp_kind }
  where
    (LHsType GhcRn
hs_fun_ty, HsFamEqnPats GhcRn
hs_args) = HsType GhcRn -> (LHsType GhcRn, HsFamEqnPats GhcRn)
splitHsAppTys HsType GhcRn
rn_ty

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

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

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

        empty_subst :: Subst
empty_subst = InScopeSet -> Subst
mkEmptySubst (InScopeSet -> Subst) -> InScopeSet -> Subst
forall a b. (a -> b) -> a -> b
$ TyVarSet -> InScopeSet
mkInScopeSet (TyVarSet -> InScopeSet) -> TyVarSet -> InScopeSet
forall a b. (a -> b) -> a -> b
$
                      Type -> TyVarSet
tyCoVarsOfType Type
fun_ki

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

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

      ---------------- No user-written args left. We're done!
      ([], Maybe (PiTyVarBinder, Type)
_) -> (Type, Type) -> TcM (Type, Type)
forall a. a -> IOEnv (Env TcGblEnv TcLclEnv) a
forall (m :: * -> *) a. Monad m => a -> m a
return (Type
fun, HasDebugCallStack => Subst -> Type -> Type
Subst -> Type -> Type
substTy Subst
subst Type
fun_ki)

      ---------------- HsArgPar: We don't care about parens here
      (HsArgPar XArgPar GhcRn
_ : [HsArg
   GhcRn
   (GenLocated SrcSpanAnnA (HsType GhcRn))
   (GenLocated SrcSpanAnnA (HsType GhcRn))]
args, Maybe (PiTyVarBinder, Type)
_) -> Int
-> Type -> Subst -> Type -> HsFamEqnPats GhcRn -> TcM (Type, Type)
go Int
n Type
fun Subst
subst Type
fun_ki HsFamEqnPats GhcRn
[HsArg
   GhcRn
   (GenLocated SrcSpanAnnA (HsType GhcRn))
   (GenLocated SrcSpanAnnA (HsType GhcRn))]
args

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

        -- FunTy with PredTy on LHS, or ForAllTy with Inferred
        Named (Bndr TcTyVar
kv ForAllTyFlag
Inferred)         -> TcTyVar -> Type -> TcM (Type, Type)
instantiate TcTyVar
kv Type
inner_ki

        Named (Bndr TcTyVar
_ ForAllTyFlag
Specified) ->  -- Visible kind application
          do { String -> SDoc -> TcM ()
traceTc String
"tcInferTyApps (vis kind app)"
                       ([SDoc] -> SDoc
forall doc. IsDoc doc => [doc] -> doc
vcat [ PiTyVarBinder -> SDoc
forall a. Outputable a => a -> SDoc
ppr PiTyVarBinder
ki_binder, GenLocated SrcSpanAnnA (HsType GhcRn) -> SDoc
forall a. Outputable a => a -> SDoc
ppr GenLocated SrcSpanAnnA (HsType GhcRn)
hs_ki_arg
                             , Type -> SDoc
forall a. Outputable a => a -> SDoc
ppr (PiTyVarBinder -> Type
piTyBinderType PiTyVarBinder
ki_binder)
                             , Subst -> SDoc
forall a. Outputable a => a -> SDoc
ppr Subst
subst ])

             ; let exp_kind :: Type
exp_kind = HasDebugCallStack => Subst -> Type -> Type
Subst -> Type -> Type
substTy Subst
subst (Type -> Type) -> Type -> Type
forall a b. (a -> b) -> a -> b
$ PiTyVarBinder -> Type
piTyBinderType PiTyVarBinder
ki_binder
             ; arg_mode <- TypeOrKind -> HoleMode -> TcM TcTyMode
mkHoleMode TypeOrKind
KindLevel HoleMode
HM_VTA
                   -- HM_VKA: see Note [Wildcards in visible kind application]
             ; ki_arg <- addErrCtxt (funAppCtxt orig_hs_ty hs_ki_arg n) $
                         tc_check_lhs_type arg_mode hs_ki_arg exp_kind

             ; traceTc "tcInferTyApps (vis kind app)" (ppr exp_kind)
             ; (subst', fun') <- mkAppTyM subst fun ki_binder ki_arg
             ; go (n+1) fun' subst' inner_ki hs_args }

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

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

      ---------------- HsValArg: a normal argument (fun ty)
      (HsValArg XValArg GhcRn
_ GenLocated SrcSpanAnnA (HsType GhcRn)
arg : [HsArg
   GhcRn
   (GenLocated SrcSpanAnnA (HsType GhcRn))
   (GenLocated SrcSpanAnnA (HsType GhcRn))]
args, Just (PiTyVarBinder
ki_binder, Type
inner_ki))
        -- next binder is invisible; need to instantiate it
        | Named (Bndr TcTyVar
kv ForAllTyFlag
flag) <- PiTyVarBinder
ki_binder
        , ForAllTyFlag -> Bool
isInvisibleForAllTyFlag ForAllTyFlag
flag   -- ForAllTy with Inferred or Specified
         -> TcTyVar -> Type -> TcM (Type, Type)
instantiate TcTyVar
kv Type
inner_ki

        -- "normal" case
        | Bool
otherwise
         -> do { String -> SDoc -> TcM ()
traceTc String
"tcInferTyApps (vis normal app)"
                          ([SDoc] -> SDoc
forall doc. IsDoc doc => [doc] -> doc
vcat [ PiTyVarBinder -> SDoc
forall a. Outputable a => a -> SDoc
ppr PiTyVarBinder
ki_binder
                                , GenLocated SrcSpanAnnA (HsType GhcRn) -> SDoc
forall a. Outputable a => a -> SDoc
ppr GenLocated SrcSpanAnnA (HsType GhcRn)
arg
                                , Type -> SDoc
forall a. Outputable a => a -> SDoc
ppr (PiTyVarBinder -> Type
piTyBinderType PiTyVarBinder
ki_binder)
                                , Subst -> SDoc
forall a. Outputable a => a -> SDoc
ppr Subst
subst ])
                ; let exp_kind :: Type
exp_kind = HasDebugCallStack => Subst -> Type -> Type
Subst -> Type -> Type
substTy Subst
subst (Type -> Type) -> Type -> Type
forall a b. (a -> b) -> a -> b
$ PiTyVarBinder -> Type
piTyBinderType PiTyVarBinder
ki_binder
                ; arg' <- SDoc -> TcM Type -> TcM Type
forall a. SDoc -> TcM a -> TcM a
addErrCtxt (GenLocated SrcSpanAnnA (HsType GhcRn)
-> GenLocated SrcSpanAnnA (HsType GhcRn) -> Int -> SDoc
forall fun arg.
(Outputable fun, Outputable arg) =>
fun -> arg -> Int -> SDoc
funAppCtxt LHsType GhcRn
GenLocated SrcSpanAnnA (HsType GhcRn)
orig_hs_ty GenLocated SrcSpanAnnA (HsType GhcRn)
arg Int
n) (TcM Type -> TcM Type) -> TcM Type -> TcM Type
forall a b. (a -> b) -> a -> b
$
                          TcTyMode -> LHsType GhcRn -> Type -> TcM Type
tc_check_lhs_type TcTyMode
mode LHsType GhcRn
GenLocated SrcSpanAnnA (HsType GhcRn)
arg Type
exp_kind
                ; traceTc "tcInferTyApps (vis normal app) 2" (ppr exp_kind)
                ; (subst', fun') <- mkAppTyM subst fun ki_binder arg'
                ; go (n+1) fun' subst' inner_ki args }

          -- no binder; try applying the substitution, or infer another arrow in fun kind
      (HsValArg XValArg GhcRn
_ GenLocated SrcSpanAnnA (HsType GhcRn)
_ : [HsArg
   GhcRn
   (GenLocated SrcSpanAnnA (HsType GhcRn))
   (GenLocated SrcSpanAnnA (HsType GhcRn))]
_, Maybe (PiTyVarBinder, Type)
Nothing)
        -> TcM (Type, Type) -> TcM (Type, Type)
try_again_after_substing_or (TcM (Type, Type) -> TcM (Type, Type))
-> TcM (Type, Type) -> TcM (Type, Type)
forall a b. (a -> b) -> a -> b
$
           do { let arrows_needed :: Int
arrows_needed = [HsArg
   GhcRn
   (GenLocated SrcSpanAnnA (HsType GhcRn))
   (GenLocated SrcSpanAnnA (HsType GhcRn))]
-> Int
forall p tm ty. [HsArg p tm ty] -> Int
n_initial_val_args HsFamEqnPats GhcRn
[HsArg
   GhcRn
   (GenLocated SrcSpanAnnA (HsType GhcRn))
   (GenLocated SrcSpanAnnA (HsType GhcRn))]
all_args
              ; co <- TypedThing -> Int -> Type -> TcM Coercion
matchExpectedFunKind (HsType GhcRn -> TypedThing
HsTypeRnThing (HsType GhcRn -> TypedThing) -> HsType GhcRn -> TypedThing
forall a b. (a -> b) -> a -> b
$ GenLocated SrcSpanAnnA (HsType GhcRn) -> HsType GhcRn
forall l e. GenLocated l e -> e
unLoc LHsType GhcRn
GenLocated SrcSpanAnnA (HsType GhcRn)
hs_ty) Int
arrows_needed Type
substed_fun_ki

              ; fun' <- liftZonkM $ zonkTcType (fun `mkCastTy` co)
                     -- This zonk is essential, to expose the fruits
                     -- of matchExpectedFunKind to the 'go' loop

              ; traceTc "tcInferTyApps (no binder)" $
                   vcat [ ppr fun <+> dcolon <+> ppr fun_ki
                        , ppr arrows_needed
                        , ppr co
                        , ppr fun' <+> dcolon <+> ppr (typeKind fun')]
              ; go_init n fun' all_args }
                -- Use go_init to establish go's INVARIANT
      where
        instantiate :: TcTyVar -> Type -> TcM (Type, Type)
instantiate TcTyVar
ki_binder Type
inner_ki
          = do { String -> SDoc -> TcM ()
traceTc String
"tcInferTyApps (need to instantiate)"
                         ([SDoc] -> SDoc
forall doc. IsDoc doc => [doc] -> doc
vcat [ TcTyVar -> SDoc
forall a. Outputable a => a -> SDoc
ppr TcTyVar
ki_binder, Subst -> SDoc
forall a. Outputable a => a -> SDoc
ppr Subst
subst])
               ; (subst', arg') <- Subst -> TcTyVar -> TcM (Subst, Type)
tcInstInvisibleTyBinder Subst
subst TcTyVar
ki_binder
               ; go n (mkAppTy fun arg') subst' inner_ki all_args }
                 -- Because tcInvisibleTyBinder instantiate ki_binder,
                 -- the kind of arg' will have the same shape as the kind
                 -- of ki_binder.  So we don't need mkAppTyM here.

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

        zapped_subst :: Subst
zapped_subst   = Subst -> Subst
zapSubst Subst
subst
        substed_fun_ki :: Type
substed_fun_ki = HasDebugCallStack => Subst -> Type -> Type
Subst -> Type -> Type
substTy Subst
subst Type
fun_ki
        hs_ty :: LHsType GhcRn
hs_ty          = LHsType GhcRn -> HsFamEqnPats GhcRn -> LHsType GhcRn
appTypeToArg LHsType GhcRn
orig_hs_ty (Int
-> [HsArg
      GhcRn
      (GenLocated SrcSpanAnnA (HsType GhcRn))
      (GenLocated SrcSpanAnnA (HsType GhcRn))]
-> [HsArg
      GhcRn
      (GenLocated SrcSpanAnnA (HsType GhcRn))
      (GenLocated SrcSpanAnnA (HsType GhcRn))]
forall a. Int -> [a] -> [a]
take (Int
nInt -> Int -> Int
forall a. Num a => a -> a -> a
-Int
1) HsFamEqnPats GhcRn
[HsArg
   GhcRn
   (GenLocated SrcSpanAnnA (HsType GhcRn))
   (GenLocated SrcSpanAnnA (HsType GhcRn))]
orig_hs_args)

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

    ty_app_err :: GenLocated SrcSpanAnnA (HsType GhcRn) -> Type -> TcRn a
ty_app_err GenLocated SrcSpanAnnA (HsType GhcRn)
arg Type
ty
      = TcRnMessage -> TcRn a
forall a. TcRnMessage -> TcM a
failWith (TcRnMessage -> TcRn a) -> TcRnMessage -> TcRn a
forall a b. (a -> b) -> a -> b
$ LHsType GhcRn -> Type -> TcRnMessage
TcRnInvalidVisibleKindArgument LHsType GhcRn
GenLocated SrcSpanAnnA (HsType GhcRn)
arg Type
ty

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


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

mkAppTyM Subst
subst Type
fun (Named (Bndr TcTyVar
tv ForAllTyFlag
_)) Type
arg
  = do { arg' <- if TcTyVar -> Bool
isTrickyTvBinder TcTyVar
tv
                 then -- See Note [mkAppTyM]: Nasty case 1
                      ZonkM Type -> TcM Type
forall a. ZonkM a -> TcM a
liftZonkM (ZonkM Type -> TcM Type) -> ZonkM Type -> TcM Type
forall a b. (a -> b) -> a -> b
$ Type -> ZonkM Type
zonkTcType Type
arg
                 else Type -> TcM Type
forall a. a -> IOEnv (Env TcGblEnv TcLclEnv) a
forall (m :: * -> *) a. Monad m => a -> m a
return     Type
arg
       ; return ( extendTvSubstAndInScope subst tv arg'
                , mk_app_ty fun arg' ) }

mk_app_ty :: TcType -> TcType -> TcType
-- This function just adds an ASSERT for mkAppTyM's precondition
mk_app_ty :: Type -> Type -> Type
mk_app_ty Type
fun Type
arg
  = Bool -> SDoc -> Type -> Type
forall a. HasCallStack => Bool -> SDoc -> a -> a
assertPpr (Type -> Bool
isPiTy Type
fun_kind)
              (Type -> SDoc
forall a. Outputable a => a -> SDoc
ppr Type
fun SDoc -> SDoc -> SDoc
forall doc. IsLine doc => doc -> doc -> doc
<+> SDoc
dcolon SDoc -> SDoc -> SDoc
forall doc. IsLine doc => doc -> doc -> doc
<+> Type -> SDoc
forall a. Outputable a => a -> SDoc
ppr Type
fun_kind SDoc -> SDoc -> SDoc
forall doc. IsDoc doc => doc -> doc -> doc
$$ Type -> SDoc
forall a. Outputable a => a -> SDoc
ppr Type
arg) (Type -> Type) -> Type -> Type
forall a b. (a -> b) -> a -> b
$
    Type -> Type -> Type
mkAppTy Type
fun Type
arg
  where
    fun_kind :: Type
fun_kind = HasDebugCallStack => Type -> Type
Type -> Type
typeKind Type
fun

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

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

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

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

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

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

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

The absence of this caused #14174 and #14520.

The calls to mkAppTyM is the other place we are very careful; see Note [mkAppTyM].

Wrinkle around FunTy:
Note that the PKTI does *not* guarantee anything about the shape of FunTys.
Specifically, when we have (FunTy vis mult arg res), it should be the case
that arg :: TYPE rr1 and res :: TYPE rr2, for some rr1 and rr2. However, we
might not have this. Example: if the user writes (a -> b), then we might
invent a :: kappa1 and b :: kappa2. We soon will check whether kappa1 ~ TYPE rho1
(for some rho1), and that will lead to kappa1 := TYPE rho1 (ditto for kappa2).
However, when we build the FunTy, we might not have zonked `a`, and so the
FunTy will be built without being able to purely extract the RuntimeReps.

Because the PKTI does not guarantee that the RuntimeReps are available in a FunTy,
we must be aware of this when splitting: splitTyConApp and splitAppTy will *not*
split a FunTy if the RuntimeReps are not available. See also Note [Decomposing FunTy]
in GHC.Tc.Solver.Equality.

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

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

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

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

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


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

saturateFamApp :: Type -> Type -> TcM (Type, Type)
saturateFamApp Type
ty Type
kind
  | Just (TyCon
tc, [Type]
args) <- HasDebugCallStack => Type -> Maybe (TyCon, [Type])
Type -> Maybe (TyCon, [Type])
tcSplitTyConApp_maybe Type
ty
  , TyCon -> Bool
tyConMustBeSaturated TyCon
tc
  , let n_to_inst :: Int
n_to_inst = TyCon -> Int
tyConArity TyCon
tc Int -> Int -> Int
forall a. Num a => a -> a -> a
- [Type] -> Int
forall a. [a] -> Int
forall (t :: * -> *) a. Foldable t => t a -> Int
length [Type]
args
  = do { (extra_args, ki') <- Int -> Type -> TcM ([Type], Type)
tcInstInvisibleTyBindersN Int
n_to_inst Type
kind
       ; return (ty `mkAppTys` extra_args, ki') }
  | Bool
otherwise
  = (Type, Type) -> TcM (Type, Type)
forall a. a -> IOEnv (Env TcGblEnv TcLclEnv) a
forall (m :: * -> *) a. Monad m => a -> m a
return (Type
ty, Type
kind)

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

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

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

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

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

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

appTypeToArg :: LHsType GhcRn -> [LHsTypeArg GhcRn] -> LHsType GhcRn
appTypeToArg :: LHsType GhcRn -> HsFamEqnPats GhcRn -> LHsType GhcRn
appTypeToArg LHsType GhcRn
f []                       = LHsType GhcRn
f
appTypeToArg LHsType GhcRn
f (HsValArg XValArg GhcRn
_ LHsType GhcRn
arg   : HsFamEqnPats GhcRn
args) = LHsType GhcRn -> HsFamEqnPats GhcRn -> LHsType GhcRn
appTypeToArg (LHsType GhcRn -> LHsType GhcRn -> LHsType GhcRn
forall (p :: Pass).
LHsType (GhcPass p) -> LHsType (GhcPass p) -> LHsType (GhcPass p)
mkHsAppTy LHsType GhcRn
f LHsType GhcRn
arg) HsFamEqnPats GhcRn
args
appTypeToArg LHsType GhcRn
f (HsArgPar XArgPar GhcRn
_       : HsFamEqnPats GhcRn
args) = LHsType GhcRn -> HsFamEqnPats GhcRn -> LHsType GhcRn
appTypeToArg LHsType GhcRn
f                 HsFamEqnPats GhcRn
args
appTypeToArg LHsType GhcRn
f (HsTypeArg XTypeArg GhcRn
_ LHsType GhcRn
arg  : HsFamEqnPats GhcRn
args)
  = LHsType GhcRn -> HsFamEqnPats GhcRn -> LHsType GhcRn
appTypeToArg (XAppKindTy GhcRn -> LHsType GhcRn -> LHsType GhcRn -> LHsType GhcRn
forall (p :: Pass).
XAppKindTy (GhcPass p)
-> LHsType (GhcPass p)
-> LHsType (GhcPass p)
-> LHsType (GhcPass p)
mkHsAppKindTy XAppKindTy GhcRn
NoExtField
noExtField LHsType GhcRn
f LHsType GhcRn
arg) HsFamEqnPats GhcRn
args


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

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

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

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

       ; traceTc "checkExpectedKindX" $
         vcat [ ppr hs_ty
              , text "act_kind':" <+> ppr act_kind'
              , text "exp_kind:" <+> ppr exp_kind ]

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

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


-- tyr <- checkExpKind hs_ty ty (act_ki :: Kind) (exp_ki :: ExpKind)
--     requires that `ty` has kind `act_ki`
-- It checks that the actual kind `act_ki` matches the expected kind `exp_ki`
-- and returns `tyr`, a possibly-casted form of `ty`, that has precisely kind `exp_ki`
-- `hs_ty` is purely for error messages
checkExpKind :: HsType GhcRn -> TcType -> TcKind -> ExpKind -> TcM TcType
checkExpKind :: HsType GhcRn -> Type -> Type -> ExpSigmaType -> TcM Type
checkExpKind HsType GhcRn
rn_ty Type
ty Type
ki (Check Type
ki') =
  HasDebugCallStack =>
HsType GhcRn -> Type -> Type -> Type -> TcM Type
HsType GhcRn -> Type -> Type -> Type -> TcM Type
checkExpectedKind HsType GhcRn
rn_ty Type
ty Type
ki Type
ki'
checkExpKind HsType GhcRn
_rn_ty Type
ty Type
ki (Infer InferResult
cell) = do
  co <- Type -> InferResult -> TcM Coercion
fillInferResult Type
ki InferResult
cell
  pure (ty `mkCastTy` co)

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

tcHsContext :: Maybe (LHsContext GhcRn) -> TcM [PredType]
tcHsContext :: Maybe (LHsContext GhcRn) -> TcM [Type]
tcHsContext Maybe (LHsContext GhcRn)
Nothing    = [Type] -> TcM [Type]
forall a. a -> IOEnv (Env TcGblEnv TcLclEnv) a
forall (m :: * -> *) a. Monad m => a -> m a
return []
tcHsContext (Just LHsContext GhcRn
cxt) = TcTyMode -> LHsContext GhcRn -> TcM [Type]
tc_hs_context TcTyMode
typeLevelMode LHsContext GhcRn
cxt

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

tc_hs_context :: TcTyMode -> LHsContext GhcRn -> TcM [PredType]
tc_hs_context :: TcTyMode -> LHsContext GhcRn -> TcM [Type]
tc_hs_context TcTyMode
mode LHsContext GhcRn
ctxt = (GenLocated SrcSpanAnnA (HsType GhcRn) -> TcM Type)
-> [GenLocated SrcSpanAnnA (HsType GhcRn)] -> TcM [Type]
forall (t :: * -> *) (m :: * -> *) a b.
(Traversable t, Monad m) =>
(a -> m b) -> t a -> m (t b)
forall (m :: * -> *) a b. Monad m => (a -> m b) -> [a] -> m [b]
mapM (TcTyMode -> LHsType GhcRn -> TcM Type
tc_lhs_pred TcTyMode
mode) (GenLocated SrcSpanAnnC [GenLocated SrcSpanAnnA (HsType GhcRn)]
-> [GenLocated SrcSpanAnnA (HsType GhcRn)]
forall l e. GenLocated l e -> e
unLoc LHsContext GhcRn
GenLocated SrcSpanAnnC [GenLocated SrcSpanAnnA (HsType GhcRn)]
ctxt)

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

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

           -- See Note [Recursion through the kinds]
           (TcTyThing -> Maybe TyCon
tcTyThingTyCon_maybe -> Just TyCon
tc) -- TyCon or TcTyCon
             -> (Type, Type) -> TcM (Type, Type)
forall a. a -> IOEnv (Env TcGblEnv TcLclEnv) a
forall (m :: * -> *) a. Monad m => a -> m a
return (TyCon -> Type
mkTyConTy TyCon
tc, TyCon -> Type
tyConKind TyCon
tc)

           AGlobal (AConLike (RealDataCon DataCon
dc))
             -> do { Bool -> TcM () -> TcM ()
forall (f :: * -> *). Applicative f => Bool -> f () -> f ()
when (TyCon -> Bool
isFamInstTyCon (DataCon -> TyCon
dataConTyCon DataCon
dc)) (TcM () -> TcM ()) -> TcM () -> TcM ()
forall a b. (a -> b) -> a -> b
$
                       -- see #15245
                       Name -> PromotionErr -> TcM ()
forall a. Name -> PromotionErr -> TcM a
promotionErr Name
name PromotionErr
FamDataConPE
                   ; let ([TcTyVar]
_, [TcTyVar]
_, [EqSpec]
_, [Type]
theta, [Scaled Type]
_, Type
_) = DataCon
-> ([TcTyVar], [TcTyVar], [EqSpec], [Type], [Scaled Type], Type)
dataConFullSig DataCon
dc
                   ; String -> SDoc -> TcM ()
traceTc String
"tcTyVar" (DataCon -> SDoc
forall a. Outputable a => a -> SDoc
ppr DataCon
dc SDoc -> SDoc -> SDoc
forall doc. IsLine doc => doc -> doc -> doc
<+> [Type] -> SDoc
forall a. Outputable a => a -> SDoc
ppr [Type]
theta)
                     -- promotionErr: Note [No constraints in kinds] in GHC.Tc.Validity
                   ; Bool -> TcM () -> TcM ()
forall (f :: * -> *). Applicative f => Bool -> f () -> f ()
unless ([Type] -> Bool
forall a. [a] -> Bool
forall (t :: * -> *) a. Foldable t => t a -> Bool
null [Type]
theta) (TcM () -> TcM ()) -> TcM () -> TcM ()
forall a b. (a -> b) -> a -> b
$
                     Name -> PromotionErr -> TcM ()
forall a. Name -> PromotionErr -> TcM a
promotionErr Name
name ([Type] -> PromotionErr
ConstrainedDataConPE [Type]
theta)
                   ; let tc :: TyCon
tc = DataCon -> TyCon
promoteDataCon DataCon
dc
                   ; (Type, Type) -> TcM (Type, Type)
forall a. a -> IOEnv (Env TcGblEnv TcLclEnv) a
forall (m :: * -> *) a. Monad m => a -> m a
return (TyCon -> [Type] -> Type
mkTyConApp TyCon
tc [], TyCon -> Type
tyConKind TyCon
tc) }

           AGlobal AnId{}    -> Name -> PromotionErr -> TcM (Type, Type)
forall a. Name -> PromotionErr -> TcM a
promotionErr Name
name PromotionErr
TermVariablePE
           ATcId{}           -> Name -> PromotionErr -> TcM (Type, Type)
forall a. Name -> PromotionErr -> TcM a
promotionErr Name
name PromotionErr
TermVariablePE
           APromotionErr PromotionErr
err -> Name -> PromotionErr -> TcM (Type, Type)
forall a. Name -> PromotionErr -> TcM a
promotionErr Name
name PromotionErr
err

           TcTyThing
_  -> WrongThingSort -> TcTyThing -> Name -> TcM (Type, Type)
forall a. WrongThingSort -> TcTyThing -> Name -> TcM a
wrongThingErr WrongThingSort
WrongThingType TcTyThing
thing Name
name }

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

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

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

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

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

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

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

Note [Body kind of a HsForAllTy]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
The body of a forall is usually a type.
Because of representation polymorphism, it can be a TYPE r, for any r.
(In fact, GHC can itself construct a function with an
unboxed tuple inside a for-all via CPR analysis; see
typecheck/should_compile/tc170).

A forall can also be used in an instance head, then the body should
be a constraint.

Right now, we do not have any easy way to enforce that a type is
either a TYPE something or CONSTRAINT something, so we accept any kind.
This is unsound (#22063). We could fix this by implementing a TypeLike
predicate, see #20000.

For a forall with a required argument, we do not allow constraints;
e.g. forall a -> Eq a is invalid. Therefore, we can enforce that the body
is a TYPE something in this case (#24176).

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

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

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

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

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

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

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

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

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

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

  * It transforms from HsType to Type

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

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

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

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

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

-}

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


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

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

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

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

       ; traceTc "tcAnonWildCardOcc" (ppr hole_lvl <+> ppr emit_holes)
       ; when emit_holes $
         emitAnonTypeHole is_extra wc_tv
         -- Why the 'when' guard?
         -- See Note [Wildcards in visible kind application]

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

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

tcAnonWildCardOcc IsExtraConstraint
is_extra TcTyMode
_ HsType GhcRn
_ Type
_
-- mode_holes is Nothing. This means we have an anonymous wildcard
-- in an unexpected place. The renamer rejects these wildcards in 'checkAnonWildcard',
-- but it is possible for a wildcard to be introduced by a Template Haskell splice,
-- as per #15433. To account for this, we throw a generic catch-all error message.
  = TcRnMessage -> TcM Type
forall a. TcRnMessage -> TcM a
failWith (TcRnMessage -> TcM Type) -> TcRnMessage -> TcM Type
forall a b. (a -> b) -> a -> b
$ Maybe Name -> BadAnonWildcardContext -> TcRnMessage
TcRnIllegalWildcardInType Maybe Name
forall a. Maybe a
Nothing BadAnonWildcardContext
reason
    where
      reason :: BadAnonWildcardContext
reason =
        case IsExtraConstraint
is_extra of
          IsExtraConstraint
YesExtraConstraint ->
            SoleExtraConstraintWildcardAllowed -> BadAnonWildcardContext
ExtraConstraintWildcardNotAllowed
              SoleExtraConstraintWildcardAllowed
SoleExtraConstraintWildcardNotAllowed
          IsExtraConstraint
NoExtraConstraint  ->
            BadAnonWildcardContext
WildcardsNotAllowedAtAll

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

kcCheckDeclHeader_cusk
  :: Name               -- ^ of the thing being checked
  -> TyConFlavour TyCon -- ^ What sort of 'TyCon' is being checked
  -> LHsQTyVars GhcRn   -- ^ Binders in the header
  -> TcM ContextKind    -- ^ The result kind
  -> TcM PolyTcTyCon    -- ^ A suitably-kinded generalized TcTyCon
kcCheckDeclHeader_cusk :: Name
-> TyConFlavour TyCon
-> LHsQTyVars GhcRn
-> TcM ContextKind
-> TcM TyCon
kcCheckDeclHeader_cusk Name
name TyConFlavour TyCon
flav
              (HsQTvs { hsq_ext :: forall pass. LHsQTyVars pass -> XHsQTvs pass
hsq_ext = XHsQTvs GhcRn
kv_ns
                      , hsq_explicit :: forall pass.
LHsQTyVars pass -> [LHsTyVarBndr (HsBndrVis pass) pass]
hsq_explicit = [LHsTyVarBndr (HsBndrVis GhcRn) GhcRn]
hs_tvs }) TcM ContextKind
kc_res_ki
  -- CUSK case
  -- See Note [Required, Specified, and Inferred for types] in GHC.Tc.TyCl
  = Name -> TyConFlavour TyCon -> TcM TyCon -> TcM TyCon
forall tc a. Name -> TyConFlavour tc -> TcM a -> TcM a
addTyConFlavCtxt Name
name TyConFlavour TyCon
flav (TcM TyCon -> TcM TyCon) -> TcM TyCon -> TcM TyCon
forall a b. (a -> b) -> a -> b
$
    do { skol_info <- SkolemInfoAnon -> IOEnv (Env TcGblEnv TcLclEnv) SkolemInfo
forall (m :: * -> *). MonadIO m => SkolemInfoAnon -> m SkolemInfo
mkSkolemInfo SkolemInfoAnon
skol_info_anon
       ; (tclvl, wanted, (scoped_kvs, (tc_bndrs, res_kind)))
           <- pushLevelAndSolveEqualitiesX "kcCheckDeclHeader_cusk" $
              bindImplicitTKBndrs_Q_Skol skol_info kv_ns                      $
              bindExplicitTKBndrs_Q_Skol skol_info ctxt_kind hs_tvs           $
              newExpectedKind =<< kc_res_ki

           -- Now, because we're in a CUSK,
           -- we quantify over the mentioned kind vars
       ; let spec_req_tkvs = [TcTyVar]
scoped_kvs [TcTyVar] -> [TcTyVar] -> [TcTyVar]
forall a. [a] -> [a] -> [a]
++ [VarBndr TcTyVar (HsBndrVis GhcRn)] -> [TcTyVar]
forall tv argf. [VarBndr tv argf] -> [tv]
binderVars [VarBndr TcTyVar (HsBndrVis GhcRn)]
tc_bndrs
             all_kinds     = Type
res_kind Type -> [Type] -> [Type]
forall a. a -> [a] -> [a]
: (TcTyVar -> Type) -> [TcTyVar] -> [Type]
forall a b. (a -> b) -> [a] -> [b]
map TcTyVar -> Type
tyVarKind [TcTyVar]
spec_req_tkvs

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

       ; inferred <- quantifyTyVars skol_info DefaultNonStandardTyVars $
                     candidates `delCandidates` spec_req_tkvs
                     -- NB: 'inferred' comes back sorted in dependency order

       ; (scoped_kvs, tc_bndrs, res_kind) <- liftZonkM $
          do { scoped_kvs <- mapM zonkTyCoVarKind scoped_kvs      -- scoped_kvs and tc_bndrs are skolems,
             ; tc_bndrs   <- mapM zonkTyCoVarBndrKind tc_bndrs    -- so zonkTyCoVarBndrKind suffices
             ; res_kind   <- zonkTcType res_kind
             ; return (scoped_kvs, tc_bndrs, res_kind) }

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

             all_tcbs =  ForAllTyFlag -> [TcTyVar] -> [TyConBinder]
mkNamedTyConBinders ForAllTyFlag
Inferred  [TcTyVar]
inferred
                      [TyConBinder] -> [TyConBinder] -> [TyConBinder]
forall a. [a] -> [a] -> [a]
++ ForAllTyFlag -> [TcTyVar] -> [TyConBinder]
mkNamedTyConBinders ForAllTyFlag
Specified [TcTyVar]
specified
                      [TyConBinder] -> [TyConBinder] -> [TyConBinder]
forall a. [a] -> [a] -> [a]
++ (VarBndr TcTyVar (HsBndrVis GhcRn) -> TyConBinder)
-> [VarBndr TcTyVar (HsBndrVis GhcRn)] -> [TyConBinder]
forall a b. (a -> b) -> [a] -> [b]
map (TyVarSet -> VarBndr TcTyVar (HsBndrVis GhcRn) -> TyConBinder
mkExplicitTyConBinder TyVarSet
mentioned_kv_set) [VarBndr TcTyVar (HsBndrVis GhcRn)]
tc_bndrs

       -- Eta expand if necessary; we are building a PolyTyCon
       ; (eta_tcbs, res_kind) <- etaExpandAlgTyCon flav skol_info all_tcbs res_kind

       ; let all_tv_prs = [TcTyVar] -> [(Name, TcTyVar)]
mkTyVarNamePairs ([TcTyVar]
scoped_kvs [TcTyVar] -> [TcTyVar] -> [TcTyVar]
forall a. [a] -> [a] -> [a]
++ [VarBndr TcTyVar (HsBndrVis GhcRn)] -> [TcTyVar]
forall tv argf. [VarBndr tv argf] -> [tv]
binderVars [VarBndr TcTyVar (HsBndrVis GhcRn)]
tc_bndrs)
             final_tcbs = [TyConBinder]
all_tcbs [TyConBinder] -> [TyConBinder] -> [TyConBinder]
forall a. [a] -> [a] -> [a]
`chkAppend` [TyConBinder]
eta_tcbs
             tycon = Name
-> [TyConBinder]
-> Type
-> [(Name, TcTyVar)]
-> Bool
-> TyConFlavour TyCon
-> TyCon
mkTcTyCon Name
name [TyConBinder]
final_tcbs Type
res_kind [(Name, TcTyVar)]
all_tv_prs
                               Bool
True -- Make a PolyTcTyCon, fully generalised
                               TyConFlavour TyCon
flav

       ; reportUnsolvedEqualities skol_info (binderVars final_tcbs)
                                  tclvl wanted

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

       ; traceTc "kcCheckDeclHeader_cusk " $
         vcat [ text "name" <+> ppr name
              , text "candidates" <+> ppr candidates
              , text "mentioned_kv_set" <+> ppr mentioned_kv_set
              , text "kv_ns" <+> ppr kv_ns
              , text "hs_tvs" <+> ppr hs_tvs
              , text "scoped_kvs" <+> ppr scoped_kvs
              , text "spec_req_tvs" <+> pprTyVars spec_req_tkvs
              , text "all_kinds" <+> ppr all_kinds
              , text "tc_tvs" <+> pprTyVars (binderVars tc_bndrs)
              , text "res_kind" <+> ppr res_kind
              , text "inferred" <+> ppr inferred
              , text "specified" <+> ppr specified
              , text "final_tcbs" <+> ppr final_tcbs
              , text "mkTyConKind final_tc_bndrs res_kind"
                <+> ppr (mkTyConKind final_tcbs res_kind)
              , text "all_tv_prs" <+> ppr all_tv_prs ]

       ; return tycon }
  where
    skol_info_anon :: SkolemInfoAnon
skol_info_anon = TyConFlavour TyCon -> Name -> SkolemInfoAnon
TyConSkol TyConFlavour TyCon
flav Name
name
    ctxt_kind :: ContextKind
ctxt_kind | TyConFlavour TyCon -> Bool
forall tc. TyConFlavour tc -> Bool
tcFlavourIsOpen TyConFlavour TyCon
flav = Type -> ContextKind
TheKind Type
liftedTypeKind
              | Bool
otherwise            = ContextKind
AnyKind

-- | Create a TyConBinder for a user-written type variable binder.
mkExplicitTyConBinder :: TyCoVarSet -- variables that are used dependently
                      -> VarBndr TyVar (HsBndrVis GhcRn)
                      -> TyConBinder
mkExplicitTyConBinder :: TyVarSet -> VarBndr TcTyVar (HsBndrVis GhcRn) -> TyConBinder
mkExplicitTyConBinder TyVarSet
dep_set (Bndr TcTyVar
tv HsBndrVis GhcRn
flag) =
  case HsBndrVis GhcRn
flag of
    HsBndrRequired{}  -> TyVarSet -> TcTyVar -> TyConBinder
mkRequiredTyConBinder TyVarSet
dep_set TcTyVar
tv
    HsBndrInvisible{} -> ForAllTyFlag -> TcTyVar -> TyConBinder
mkNamedTyConBinder ForAllTyFlag
Specified TcTyVar
tv

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

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

             tc_tvs = [VarBndr TcTyVar (HsBndrVis GhcRn)] -> [TcTyVar]
forall tv argf. [VarBndr tv argf] -> [tv]
binderVars [VarBndr TcTyVar (HsBndrVis GhcRn)]
tc_bndrs
               -- Discard visibility flags. We made sure all of them are HsBndrRequired
               -- by the call to rejectInvisibleBinders above.

             tc_binders = [TcTyVar] -> [TyConBinder]
mkAnonTyConBinders [TcTyVar]
tc_tvs
               -- This has to be mkAnonTyConBinder!
               -- See Note [No polymorphic recursion in type decls] in GHC.Tc.TyCl
               --
               -- Also, note that tc_binders has the tyvars from only the
               -- user-written type variable binders.
               -- See S1 Note [TcTyCon, MonoTcTyCon, and PolyTcTyCon] in GHC.Tc.TyCl

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

             tycon = Name
-> [TyConBinder]
-> Type
-> [(Name, TcTyVar)]
-> Bool
-> TyConFlavour TyCon
-> TyCon
mkTcTyCon Name
name [TyConBinder]
tc_binders Type
res_kind [(Name, TcTyVar)]
all_tv_prs
                               Bool
False -- Make a MonoTcTyCon
                               TyConFlavour TyCon
flav

       ; traceTc "kcInferDeclHeader: not-cusk" $
         vcat [ ppr name, ppr kv_ns, ppr hs_bndrs
              , ppr scoped_kvs
              , ppr tc_tvs, ppr (mkTyConKind tc_binders res_kind) ]
       ; return tycon }
  where
    ctxt_kind :: ContextKind
ctxt_kind | TyConFlavour TyCon -> Bool
forall tc. TyConFlavour tc -> Bool
tcFlavourIsOpen TyConFlavour TyCon
flav = Type -> ContextKind
TheKind Type
liftedTypeKind
              | Bool
otherwise            = ContextKind
AnyKind

-- rejectInvisibleBinders is called on on the inference code path; there is
-- no standalone kind signature, nor CUSK.
-- See Note [No inference for invisible binders in type decls] in GHC.Tc.TyCl
rejectInvisibleBinders :: Name -> [LHsTyVarBndr (HsBndrVis GhcRn) GhcRn] -> TcM ()
rejectInvisibleBinders :: Name -> [LHsTyVarBndr (HsBndrVis GhcRn) GhcRn] -> TcM ()
rejectInvisibleBinders Name
name = (GenLocated SrcSpanAnnA (HsTyVarBndr (HsBndrVis GhcRn) GhcRn)
 -> TcM ())
-> [GenLocated SrcSpanAnnA (HsTyVarBndr (HsBndrVis GhcRn) GhcRn)]
-> TcM ()
forall (t :: * -> *) (m :: * -> *) a b.
(Foldable t, Monad m) =>
(a -> m b) -> t a -> m ()
mapM_ LHsTyVarBndr (HsBndrVis GhcRn) GhcRn -> TcM ()
GenLocated SrcSpanAnnA (HsTyVarBndr (HsBndrVis GhcRn) GhcRn)
-> TcM ()
check_bndr_vis
  where
    check_bndr_vis :: LHsTyVarBndr (HsBndrVis GhcRn) GhcRn -> TcM ()
    check_bndr_vis :: LHsTyVarBndr (HsBndrVis GhcRn) GhcRn -> TcM ()
check_bndr_vis LHsTyVarBndr (HsBndrVis GhcRn) GhcRn
bndr =
      Bool -> TcM () -> TcM ()
forall (f :: * -> *). Applicative f => Bool -> f () -> f ()
when (HsBndrVis GhcRn -> Bool
forall pass. HsBndrVis pass -> Bool
isHsBndrInvisible (HsTyVarBndr (HsBndrVis GhcRn) GhcRn -> HsBndrVis GhcRn
forall flag (pass :: Pass). HsTyVarBndr flag (GhcPass pass) -> flag
hsTyVarBndrFlag (GenLocated SrcSpanAnnA (HsTyVarBndr (HsBndrVis GhcRn) GhcRn)
-> HsTyVarBndr (HsBndrVis GhcRn) GhcRn
forall l e. GenLocated l e -> e
unLoc LHsTyVarBndr (HsBndrVis GhcRn) GhcRn
GenLocated SrcSpanAnnA (HsTyVarBndr (HsBndrVis GhcRn) GhcRn)
bndr))) (TcM () -> TcM ()) -> TcM () -> TcM ()
forall a b. (a -> b) -> a -> b
$
        TcRnMessage -> TcM ()
addErr (Name -> LHsTyVarBndr (HsBndrVis GhcRn) GhcRn -> TcRnMessage
TcRnInvisBndrWithoutSig Name
name LHsTyVarBndr (HsBndrVis GhcRn) GhcRn
bndr)

-- | Kind-check a declaration header against a standalone kind signature.
-- See Note [kcCheckDeclHeader_sig]
kcCheckDeclHeader_sig
  :: Kind               -- ^ Standalone kind signature, fully zonked! (zonkTcTypeToType)
  -> Name               -- ^ of the thing being checked
  -> TyConFlavour TyCon -- ^ What sort of 'TyCon' is being checked
  -> LHsQTyVars GhcRn   -- ^ Binders in the header
  -> TcM ContextKind    -- ^ The result kind. AnyKind == no result signature
  -> TcM PolyTcTyCon    -- ^ A suitably-kinded, fully generalised TcTyCon
-- Postcondition to (kcCheckDeclHeader_sig sig_kind n f hs_tvs kc_res_ki):
--   kind(returned PolyTcTyCon) = sig_kind
--
kcCheckDeclHeader_sig :: Type
-> Name
-> TyConFlavour TyCon
-> LHsQTyVars GhcRn
-> TcM ContextKind
-> TcM TyCon
kcCheckDeclHeader_sig Type
sig_kind Name
name TyConFlavour TyCon
flav
          (HsQTvs { hsq_ext :: forall pass. LHsQTyVars pass -> XHsQTvs pass
hsq_ext      = XHsQTvs GhcRn
implicit_nms
                  , hsq_explicit :: forall pass.
LHsQTyVars pass -> [LHsTyVarBndr (HsBndrVis pass) pass]
hsq_explicit = [LHsTyVarBndr (HsBndrVis GhcRn) GhcRn]
hs_tv_bndrs }) TcM ContextKind
kc_res_ki
  = Name -> TyConFlavour TyCon -> TcM TyCon -> TcM TyCon
forall tc a. Name -> TyConFlavour tc -> TcM a -> TcM a
addTyConFlavCtxt Name
name TyConFlavour TyCon
flav (TcM TyCon -> TcM TyCon) -> TcM TyCon -> TcM TyCon
forall a b. (a -> b) -> a -> b
$
    do { skol_info <- SkolemInfoAnon -> IOEnv (Env TcGblEnv TcLclEnv) SkolemInfo
forall (m :: * -> *). MonadIO m => SkolemInfoAnon -> m SkolemInfo
mkSkolemInfo (TyConFlavour TyCon -> Name -> SkolemInfoAnon
TyConSkol TyConFlavour TyCon
flav Name
name)
       ; (sig_tcbs :: [TcTyConBinder], sig_res_kind :: Kind)
             <- splitTyConKind skol_info emptyInScopeSet
                               (map getOccName hs_tv_bndrs) sig_kind

       ; traceTc "kcCheckDeclHeader_sig {" $
           vcat [ text "sig_kind:" <+> ppr sig_kind
                , text "sig_tcbs:" <+> ppr sig_tcbs
                , text "sig_res_kind:" <+> ppr sig_res_kind
                , text "implict_nms:" <+> ppr implicit_nms
                , text "hs_tv_bndrs:" <+> ppr hs_tv_bndrs ]

       ; (tclvl, wanted, (implicit_tvs, (skol_tcbs, skol_scoped_tvs, (extra_tcbs, tycon_res_kind))))
           <- pushLevelAndSolveEqualitiesX "kcCheckDeclHeader_sig" $  -- #16687
              bindImplicitTKBndrs_Q_Tv implicit_nms                $  -- Q means don't clone
              matchUpSigWithDecl name sig_tcbs sig_res_kind hs_tv_bndrs $ \ [TyConBinder]
excess_sig_tcbs Type
sig_res_kind ->
              do { -- Kind-check the result kind annotation, if present:
                   --    data T a b :: res_ki where ...
                   --               ^^^^^^^^^
                   -- We do it here because at this point the environment has been
                   -- extended with both 'implicit_tcv_prs' and 'explicit_tv_prs'.
                   --
                   -- Also see Note [Arity of type families and type synonyms]
                 ; res_kind :: ContextKind <- TcM ContextKind
kc_res_ki

                 ; let sig_res_kind' = [TyConBinder] -> Type -> Type
mkTyConKind [TyConBinder]
excess_sig_tcbs Type
sig_res_kind

                 ; traceTc "kcCheckDeclHeader_sig 2" $
                    vcat [ text "excess_sig_tcbs" <+> ppr excess_sig_tcbs
                         , text "res_kind" <+> ppr res_kind
                         , text "sig_res_kind'" <+> ppr sig_res_kind'
                         ]

                 -- Unify res_ki (from the type declaration) with
                 -- sig_res_kind', the residual kind from the kind signature.
                 ; checkExpectedResKind sig_res_kind' res_kind

                 -- Add more binders for data/newtype, so the result kind has no arrows
                 -- See Note [Datatype return kinds]
                 ; if null excess_sig_tcbs || not (needsEtaExpansion flav)
                   then return ([],              sig_res_kind')
                   else return (excess_sig_tcbs, sig_res_kind)
          }


        -- Check that there are no unsolved equalities
        ; let all_tcbs = [TyConBinder]
skol_tcbs [TyConBinder] -> [TyConBinder] -> [TyConBinder]
forall a. [a] -> [a] -> [a]
++ [TyConBinder]
extra_tcbs
        ; reportUnsolvedEqualities skol_info (binderVars all_tcbs) tclvl wanted

        -- Check that distinct binders map to distinct tyvars (see #20916). For example
        --    type T :: k -> k -> Type
        --    data T (a::p) (b::q) = ...
        -- Here p and q both map to the same kind variable k.  We don't allow this
        -- so we must check that they are distinct.  A similar thing happens
        -- in GHC.Tc.TyCl.swizzleTcTyConBinders during inference.
        --
        -- With visible dependent quantification, one of the binders involved
        -- may be explicit.  Consider #24604
        --    type UF :: forall zk -> zk -> Constraint
        --    class UF kk (xb :: k)
        -- Here `k` and `kk` both denote the same variable; but only `k` is implicit
        -- Hence we need to add skol_scoped_tvs
        ; implicit_tvs <- liftZonkM $ zonkTcTyVarsToTcTyVars implicit_tvs
        ; let implicit_prs = HsQTvsRn
XHsQTvs GhcRn
implicit_nms HsQTvsRn -> [TcTyVar] -> [(Name, TcTyVar)]
forall a b. [a] -> [b] -> [(a, b)]
`zip` [TcTyVar]
implicit_tvs
              dup_chk_prs  = [(Name, TcTyVar)]
implicit_prs [(Name, TcTyVar)] -> [(Name, TcTyVar)] -> [(Name, TcTyVar)]
forall a. [a] -> [a] -> [a]
++ [TcTyVar] -> [(Name, TcTyVar)]
mkTyVarNamePairs [TcTyVar]
skol_scoped_tvs
        ; unless (null implicit_nms) $  -- No need if no implicit tyvars
          checkForDuplicateScopedTyVars dup_chk_prs
        ; checkForDisconnectedScopedTyVars name flav all_tcbs implicit_prs

        -- Swizzle the Names so that the TyCon uses the user-declared implicit names
        -- E.g  type T :: k -> Type
        --      data T (a :: j) = ....
        -- We want the TyConBinders of T to be [j, a::j], not [k, a::k]
        -- Why? So that the TyConBinders of the TyCon will lexically scope over the
        -- associated types and methods of a class.
        ; let swizzle_env = [(TcTyVar, Name)] -> VarEnv Name
forall a. [(TcTyVar, a)] -> VarEnv a
mkVarEnv (((Name, TcTyVar) -> (TcTyVar, Name))
-> [(Name, TcTyVar)] -> [(TcTyVar, Name)]
forall a b. (a -> b) -> [a] -> [b]
map (Name, TcTyVar) -> (TcTyVar, Name)
forall a b. (a, b) -> (b, a)
swap [(Name, TcTyVar)]
implicit_prs)
              (subst, swizzled_tcbs) = mapAccumL (swizzleTcb swizzle_env) emptySubst all_tcbs
              swizzled_kind          = HasDebugCallStack => Subst -> Type -> Type
Subst -> Type -> Type
substTy Subst
subst Type
tycon_res_kind
              all_tv_prs             = [TcTyVar] -> [(Name, TcTyVar)]
mkTyVarNamePairs ([TyConBinder] -> [TcTyVar]
forall tv argf. [VarBndr tv argf] -> [tv]
binderVars [TyConBinder]
swizzled_tcbs)

        ; traceTc "kcCheckDeclHeader swizzle" $ vcat
          [ text "sig_tcbs ="       <+> ppr sig_tcbs
          , text "implicit_prs ="   <+> ppr implicit_prs
          , text "hs_tv_bndrs ="    <+> ppr hs_tv_bndrs
          , text "all_tcbs ="       <+> pprTyVars (binderVars all_tcbs)
          , text "swizzled_tcbs ="  <+> pprTyVars (binderVars swizzled_tcbs)
          , text "tycon_res_kind =" <+> ppr tycon_res_kind
          , text "swizzled_kind ="  <+> ppr swizzled_kind ]

        -- Build the final, generalized PolyTcTyCon
        -- NB: all_tcbs must bind the tyvars in the range of all_tv_prs
        --     because the tv_prs is used when (say) typechecking the RHS of
        --     a type synonym.
        ; let tc = Name
-> [TyConBinder]
-> Type
-> [(Name, TcTyVar)]
-> Bool
-> TyConFlavour TyCon
-> TyCon
mkTcTyCon Name
name [TyConBinder]
swizzled_tcbs Type
swizzled_kind [(Name, TcTyVar)]
all_tv_prs
                             Bool
True -- Make a PolyTcTyCon, fully generalised
                             TyConFlavour TyCon
flav

        ; traceTc "kcCheckDeclHeader_sig }" $ vcat
          [ text "tyConName = " <+> ppr (tyConName tc)
          , text "sig_kind =" <+> debugPprType sig_kind
          , text "tyConKind =" <+> debugPprType (tyConKind tc)
          , text "tyConBinders = " <+> ppr (tyConBinders tc)
          , text "tyConResKind" <+> debugPprType (tyConResKind tc)
          ]
        ; return tc }

-- | Check the result kind annotation on a type constructor against
-- the corresponding section of the standalone kind signature.
-- Drops invisible binders that interfere with unification.
checkExpectedResKind :: TcKind       -- ^ the result kind from the separate kind signature
                     -> ContextKind  -- ^ the result kind from the declaration header
                     -> TcM ()
checkExpectedResKind :: Type -> ContextKind -> TcM ()
checkExpectedResKind Type
_ ContextKind
AnyKind
  = () -> TcM ()
forall a. a -> IOEnv (Env TcGblEnv TcLclEnv) a
forall (m :: * -> *) a. Monad m => a -> m a
return ()  -- No signature in the declaration header
checkExpectedResKind Type
sig_kind ContextKind
res_ki
  = do { actual_res_ki <- ContextKind -> TcM Type
newExpectedKind ContextKind
res_ki

       ; let -- Drop invisible binders from sig_kind until they match up
             -- with res_ki.  By analogy with checkExpectedKind.
             n_res_invis_bndrs = Type -> Int
invisibleTyBndrCount Type
actual_res_ki
             n_sig_invis_bndrs = Type -> Int
invisibleTyBndrCount Type
sig_kind
             n_to_inst         = Int
n_sig_invis_bndrs Int -> Int -> Int
forall a. Num a => a -> a -> a
- Int
n_res_invis_bndrs

             (_, sig_kind') = splitInvisPiTysN n_to_inst sig_kind

       ; discardResult $ unifyKind Nothing sig_kind' actual_res_ki }

matchUpSigWithDecl
  :: Name                        -- Name of the type constructor for error messages
  -> [TcTyConBinder]             -- TcTyConBinders (with skolem TcTyVars) from the separate kind signature
  -> TcKind                      -- The tail end of the kind signature
  -> [LHsTyVarBndr (HsBndrVis GhcRn) GhcRn]     -- User-written binders in decl
  -> ([TcTyConBinder] -> TcKind -> TcM a)  -- All user-written binders are in scope
                                           --   Argument is excess TyConBinders and tail kind
  -> TcM ( [TcTyConBinder]       -- Skolemised binders, with TcTyVars
         , [TcTyVar]             -- Skolem tyvars brought into lexical scope by this matching-up
         , a )
-- See Note [Matching a kind signature with a declaration]
-- Invariant: Length of returned TyConBinders + length of excess TyConBinders
--            = length of incoming TyConBinders
matchUpSigWithDecl :: forall a.
Name
-> [TyConBinder]
-> Type
-> [LHsTyVarBndr (HsBndrVis GhcRn) GhcRn]
-> ([TyConBinder] -> Type -> TcM a)
-> TcM ([TyConBinder], [TcTyVar], a)
matchUpSigWithDecl Name
name [TyConBinder]
sig_tcbs Type
sig_res_kind [LHsTyVarBndr (HsBndrVis GhcRn) GhcRn]
hs_bndrs [TyConBinder] -> Type -> TcM a
thing_inside
  = Subst
-> [TyConBinder]
-> [GenLocated SrcSpanAnnA (HsTyVarBndr (HsBndrVis GhcRn) GhcRn)]
-> IOEnv (Env TcGblEnv TcLclEnv) ([TyConBinder], [TcTyVar], a)
go Subst
emptySubst [TyConBinder]
sig_tcbs [LHsTyVarBndr (HsBndrVis GhcRn) GhcRn]
[GenLocated SrcSpanAnnA (HsTyVarBndr (HsBndrVis GhcRn) GhcRn)]
hs_bndrs
  where
    go :: Subst
-> [TyConBinder]
-> [GenLocated SrcSpanAnnA (HsTyVarBndr (HsBndrVis GhcRn) GhcRn)]
-> IOEnv (Env TcGblEnv TcLclEnv) ([TyConBinder], [TcTyVar], a)
go Subst
subst [TyConBinder]
tcbs []
      = do { let (Subst
subst', [TyConBinder]
tcbs') = Subst -> [TyConBinder] -> (Subst, [TyConBinder])
substTyConBindersX Subst
subst [TyConBinder]
tcbs
           ; res <- [TyConBinder] -> Type -> TcM a
thing_inside [TyConBinder]
tcbs' (HasDebugCallStack => Subst -> Type -> Type
Subst -> Type -> Type
substTy Subst
subst' Type
sig_res_kind)
           ; return ([], [], res) }

    go Subst
_ [] [GenLocated SrcSpanAnnA (HsTyVarBndr (HsBndrVis GhcRn) GhcRn)]
hs_bndrs
      = TcRnMessage
-> IOEnv (Env TcGblEnv TcLclEnv) ([TyConBinder], [TcTyVar], a)
forall a. TcRnMessage -> TcM a
failWithTc (Type -> [LHsTyVarBndr (HsBndrVis GhcRn) GhcRn] -> TcRnMessage
TcRnTooManyBinders Type
sig_res_kind [LHsTyVarBndr (HsBndrVis GhcRn) GhcRn]
[GenLocated SrcSpanAnnA (HsTyVarBndr (HsBndrVis GhcRn) GhcRn)]
hs_bndrs)

    go Subst
subst (TyConBinder
tcb : [TyConBinder]
tcbs') hs_bndrs :: [GenLocated SrcSpanAnnA (HsTyVarBndr (HsBndrVis GhcRn) GhcRn)]
hs_bndrs@(GenLocated SrcSpanAnnA (HsTyVarBndr (HsBndrVis GhcRn) GhcRn)
hs_bndr : [GenLocated SrcSpanAnnA (HsTyVarBndr (HsBndrVis GhcRn) GhcRn)]
hs_bndrs')
      | TyConBndrVis -> HsBndrVis GhcRn -> Bool
zippable (TyConBinder -> TyConBndrVis
forall tv argf. VarBndr tv argf -> argf
binderFlag TyConBinder
tcb) (HsTyVarBndr (HsBndrVis GhcRn) GhcRn -> HsBndrVis GhcRn
forall flag (pass :: Pass). HsTyVarBndr flag (GhcPass pass) -> flag
hsTyVarBndrFlag (GenLocated SrcSpanAnnA (HsTyVarBndr (HsBndrVis GhcRn) GhcRn)
-> HsTyVarBndr (HsBndrVis GhcRn) GhcRn
forall l e. GenLocated l e -> e
unLoc GenLocated SrcSpanAnnA (HsTyVarBndr (HsBndrVis GhcRn) GhcRn)
hs_bndr))
      = -- Visible TyConBinder, so match up with the hs_bndrs
        do { let Bndr TcTyVar
tv TyConBndrVis
vis = TyConBinder
tcb
                 tv' :: TcTyVar
tv' = (Type -> Type) -> TcTyVar -> TcTyVar
updateTyVarKind (HasDebugCallStack => Subst -> Type -> Type
Subst -> Type -> Type
substTy Subst
subst) (TcTyVar -> TcTyVar) -> TcTyVar -> TcTyVar
forall a b. (a -> b) -> a -> b
$
                       TcTyVar -> Name -> TcTyVar
setTyVarName TcTyVar
tv (GenLocated SrcSpanAnnA (HsTyVarBndr (HsBndrVis GhcRn) GhcRn)
-> Name
forall a. NamedThing a => a -> Name
getName GenLocated SrcSpanAnnA (HsTyVarBndr (HsBndrVis GhcRn) GhcRn)
hs_bndr)
                   -- Give the skolem the Name of the HsTyVarBndr, so that if it
                   -- appears in an error message it has a name and binding site
                   -- that come from the type declaration, not the kind signature
                 subst' :: Subst
subst' = Subst -> TcTyVar -> TcTyVar -> Subst
extendTCvSubstWithClone Subst
subst TcTyVar
tv TcTyVar
tv'
           ; HsTyVarBndr (HsBndrVis GhcRn) GhcRn -> Type -> TcM ()
tc_hs_bndr (GenLocated SrcSpanAnnA (HsTyVarBndr (HsBndrVis GhcRn) GhcRn)
-> HsTyVarBndr (HsBndrVis GhcRn) GhcRn
forall l e. GenLocated l e -> e
unLoc GenLocated SrcSpanAnnA (HsTyVarBndr (HsBndrVis GhcRn) GhcRn)
hs_bndr) (TcTyVar -> Type
tyVarKind TcTyVar
tv')
           ; String -> SDoc -> TcM ()
traceTc String
"musd1" (TyConBinder -> SDoc
forall a. Outputable a => a -> SDoc
ppr TyConBinder
tcb SDoc -> SDoc -> SDoc
forall doc. IsDoc doc => doc -> doc -> doc
$$ GenLocated SrcSpanAnnA (HsTyVarBndr (HsBndrVis GhcRn) GhcRn)
-> SDoc
forall a. Outputable a => a -> SDoc
ppr GenLocated SrcSpanAnnA (HsTyVarBndr (HsBndrVis GhcRn) GhcRn)
hs_bndr SDoc -> SDoc -> SDoc
forall doc. IsDoc doc => doc -> doc -> doc
$$ TcTyVar -> SDoc
forall a. Outputable a => a -> SDoc
ppr TcTyVar
tv')
           ; (tcbs', tvs, res) <- [TcTyVar]
-> IOEnv (Env TcGblEnv TcLclEnv) ([TyConBinder], [TcTyVar], a)
-> IOEnv (Env TcGblEnv TcLclEnv) ([TyConBinder], [TcTyVar], a)
forall r. [TcTyVar] -> TcM r -> TcM r
tcExtendTyVarEnv [TcTyVar
tv'] (IOEnv (Env TcGblEnv TcLclEnv) ([TyConBinder], [TcTyVar], a)
 -> IOEnv (Env TcGblEnv TcLclEnv) ([TyConBinder], [TcTyVar], a))
-> IOEnv (Env TcGblEnv TcLclEnv) ([TyConBinder], [TcTyVar], a)
-> IOEnv (Env TcGblEnv TcLclEnv) ([TyConBinder], [TcTyVar], a)
forall a b. (a -> b) -> a -> b
$
                                  Subst
-> [TyConBinder]
-> [GenLocated SrcSpanAnnA (HsTyVarBndr (HsBndrVis GhcRn) GhcRn)]
-> IOEnv (Env TcGblEnv TcLclEnv) ([TyConBinder], [TcTyVar], a)
go Subst
subst' [TyConBinder]
tcbs' [GenLocated SrcSpanAnnA (HsTyVarBndr (HsBndrVis GhcRn) GhcRn)]
hs_bndrs'
           ; return (Bndr tv' vis : tcbs', tv':tvs, res) }
             -- We do a tcExtendTyVarEnv [tv'], so we return tv' in
             -- the list of lexically-scoped skolem type variables

      | TyConBndrVis -> Bool
skippable (TyConBinder -> TyConBndrVis
forall tv argf. VarBndr tv argf -> argf
binderFlag TyConBinder
tcb)