{-
(c) The University of Glasgow 2006
(c) The AQUA Project, Glasgow University, 1996-1998

-}

{-# LANGUAGE CPP, TupleSections, ScopedTypeVariables, MultiWayIf #-}
{-# LANGUAGE TypeFamilies #-}
{-# LANGUAGE ViewPatterns #-}

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

-- | Typecheck type and class declarations
module GHC.Tc.TyCl (
        tcTyAndClassDecls,

        -- Functions used by GHC.Tc.TyCl.Instance to check
        -- data/type family instance declarations
        kcConDecls, tcConDecls, dataDeclChecks, checkValidTyCon,
        tcFamTyPats, tcTyFamInstEqn,
        tcAddTyFamInstCtxt, tcMkDataFamInstCtxt, tcAddDataFamInstCtxt,
        unravelFamInstPats, addConsistencyConstraints,
        wrongKindOfFamily
    ) where

#include "HsVersions.h"

import GHC.Prelude

import GHC.Hs
import GHC.Driver.Types
import GHC.Tc.TyCl.Build
import GHC.Tc.Utils.Monad
import GHC.Tc.Utils.Env
import GHC.Tc.Validity
import GHC.Tc.Utils.Zonk
import GHC.Tc.TyCl.Utils
import GHC.Tc.TyCl.Class
import {-# SOURCE #-} GHC.Tc.TyCl.Instance( tcInstDecls1 )
import GHC.Tc.Deriv (DerivInfo(..))
import GHC.Tc.Utils.Unify ( checkTvConstraints )
import GHC.Tc.Gen.HsType
import GHC.Tc.Instance.Class( AssocInstInfo(..) )
import GHC.Tc.Utils.TcMType
import GHC.Builtin.Types (oneDataConTy,  unitTy, makeRecoveryTyCon )
import GHC.Tc.Utils.TcType
import GHC.Core.Multiplicity
import GHC.Rename.Env( lookupConstructorFields )
import GHC.Tc.Instance.Family
import GHC.Core.FamInstEnv
import GHC.Core.Coercion
import GHC.Tc.Types.Origin
import GHC.Core.Type
import GHC.Core.TyCo.Rep   -- for checkValidRoles
import GHC.Core.TyCo.Ppr( pprTyVars )
import GHC.Core.Class
import GHC.Core.Coercion.Axiom
import GHC.Core.TyCon
import GHC.Core.DataCon
import GHC.Types.Id
import GHC.Types.Var
import GHC.Types.Var.Env
import GHC.Types.Var.Set
import GHC.Unit.Module
import GHC.Unit.State
import GHC.Types.Name
import GHC.Types.Name.Set
import GHC.Types.Name.Env
import GHC.Utils.Outputable
import GHC.Data.Maybe
import GHC.Core.Unify
import GHC.Utils.Misc
import GHC.Types.SrcLoc
import GHC.Data.List.SetOps
import GHC.Driver.Session
import GHC.Types.Unique
import GHC.Core.ConLike( ConLike(..) )
import GHC.Types.Basic
import qualified GHC.LanguageExtensions as LangExt

import Control.Monad
import Data.Function ( on )
import Data.Functor.Identity
import Data.List
import Data.List.NonEmpty ( NonEmpty(..) )
import qualified Data.Set as Set
import Data.Tuple( swap )

{-
************************************************************************
*                                                                      *
\subsection{Type checking for type and class declarations}
*                                                                      *
************************************************************************

Note [Grouping of type and class declarations]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
tcTyAndClassDecls is called on a list of `TyClGroup`s. Each group is a strongly
connected component of mutually dependent types and classes. We kind check and
type check each group separately to enhance kind polymorphism. Take the
following example:

  type Id a = a
  data X = X (Id Int)

If we were to kind check the two declarations together, we would give Id the
kind * -> *, since we apply it to an Int in the definition of X. But we can do
better than that, since Id really is kind polymorphic, and should get kind
forall (k::*). k -> k. Since it does not depend on anything else, it can be
kind-checked by itself, hence getting the most general kind. We then kind check
X, which works fine because we then know the polymorphic kind of Id, and simply
instantiate k to *.

Note [Check role annotations in a second pass]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Role inference potentially depends on the types of all of the datacons declared
in a mutually recursive group. The validity of a role annotation, in turn,
depends on the result of role inference. Because the types of datacons might
be ill-formed (see #7175 and Note [Checking GADT return types]) we must check
*all* the tycons in a group for validity before checking *any* of the roles.
Thus, we take two passes over the resulting tycons, first checking for general
validity and then checking for valid role annotations.
-}

tcTyAndClassDecls :: [TyClGroup GhcRn]      -- Mutually-recursive groups in
                                            -- dependency order
                  -> TcM ( TcGblEnv         -- Input env extended by types and
                                            -- classes
                                            -- and their implicit Ids,DataCons
                         , [InstInfo GhcRn] -- Source-code instance decls info
                         , [DerivInfo]      -- Deriving info
                         )
-- Fails if there are any errors
tcTyAndClassDecls :: [TyClGroup GhcRn] -> TcM (TcGblEnv, [InstInfo GhcRn], [DerivInfo])
tcTyAndClassDecls [TyClGroup GhcRn]
tyclds_s
  -- The code recovers internally, but if anything gave rise to
  -- an error we'd better stop now, to avoid a cascade
  -- Type check each group in dependency order folding the global env
  = TcM (TcGblEnv, [InstInfo GhcRn], [DerivInfo])
-> TcM (TcGblEnv, [InstInfo GhcRn], [DerivInfo])
forall r. TcM r -> TcM r
checkNoErrs (TcM (TcGblEnv, [InstInfo GhcRn], [DerivInfo])
 -> TcM (TcGblEnv, [InstInfo GhcRn], [DerivInfo]))
-> TcM (TcGblEnv, [InstInfo GhcRn], [DerivInfo])
-> TcM (TcGblEnv, [InstInfo GhcRn], [DerivInfo])
forall a b. (a -> b) -> a -> b
$ [InstInfo GhcRn]
-> [DerivInfo]
-> [TyClGroup GhcRn]
-> TcM (TcGblEnv, [InstInfo GhcRn], [DerivInfo])
fold_env [] [] [TyClGroup GhcRn]
tyclds_s
  where
    fold_env :: [InstInfo GhcRn]
             -> [DerivInfo]
             -> [TyClGroup GhcRn]
             -> TcM (TcGblEnv, [InstInfo GhcRn], [DerivInfo])
    fold_env :: [InstInfo GhcRn]
-> [DerivInfo]
-> [TyClGroup GhcRn]
-> TcM (TcGblEnv, [InstInfo GhcRn], [DerivInfo])
fold_env [InstInfo GhcRn]
inst_info [DerivInfo]
deriv_info []
      = do { TcGblEnv
gbl_env <- TcRnIf TcGblEnv TcLclEnv TcGblEnv
forall gbl lcl. TcRnIf gbl lcl gbl
getGblEnv
           ; (TcGblEnv, [InstInfo GhcRn], [DerivInfo])
-> TcM (TcGblEnv, [InstInfo GhcRn], [DerivInfo])
forall (m :: * -> *) a. Monad m => a -> m a
return (TcGblEnv
gbl_env, [InstInfo GhcRn]
inst_info, [DerivInfo]
deriv_info) }
    fold_env [InstInfo GhcRn]
inst_info [DerivInfo]
deriv_info (TyClGroup GhcRn
tyclds:[TyClGroup GhcRn]
tyclds_s)
      = do { (TcGblEnv
tcg_env, [InstInfo GhcRn]
inst_info', [DerivInfo]
deriv_info') <- TyClGroup GhcRn -> TcM (TcGblEnv, [InstInfo GhcRn], [DerivInfo])
tcTyClGroup TyClGroup GhcRn
tyclds
           ; TcGblEnv
-> TcM (TcGblEnv, [InstInfo GhcRn], [DerivInfo])
-> TcM (TcGblEnv, [InstInfo GhcRn], [DerivInfo])
forall gbl lcl a. gbl -> TcRnIf gbl lcl a -> TcRnIf gbl lcl a
setGblEnv TcGblEnv
tcg_env (TcM (TcGblEnv, [InstInfo GhcRn], [DerivInfo])
 -> TcM (TcGblEnv, [InstInfo GhcRn], [DerivInfo]))
-> TcM (TcGblEnv, [InstInfo GhcRn], [DerivInfo])
-> TcM (TcGblEnv, [InstInfo GhcRn], [DerivInfo])
forall a b. (a -> b) -> a -> b
$
               -- remaining groups are typechecked in the extended global env.
             [InstInfo GhcRn]
-> [DerivInfo]
-> [TyClGroup GhcRn]
-> TcM (TcGblEnv, [InstInfo GhcRn], [DerivInfo])
fold_env ([InstInfo GhcRn]
inst_info' [InstInfo GhcRn] -> [InstInfo GhcRn] -> [InstInfo GhcRn]
forall a. [a] -> [a] -> [a]
++ [InstInfo GhcRn]
inst_info)
                      ([DerivInfo]
deriv_info' [DerivInfo] -> [DerivInfo] -> [DerivInfo]
forall a. [a] -> [a] -> [a]
++ [DerivInfo]
deriv_info)
                      [TyClGroup GhcRn]
tyclds_s }

tcTyClGroup :: TyClGroup GhcRn
            -> TcM (TcGblEnv, [InstInfo GhcRn], [DerivInfo])
-- Typecheck one strongly-connected component of type, class, and instance decls
-- See Note [TyClGroups and dependency analysis] in GHC.Hs.Decls
tcTyClGroup :: TyClGroup GhcRn -> TcM (TcGblEnv, [InstInfo GhcRn], [DerivInfo])
tcTyClGroup (TyClGroup { group_tyclds :: forall pass. TyClGroup pass -> [LTyClDecl pass]
group_tyclds = [LTyClDecl GhcRn]
tyclds
                       , group_roles :: forall pass. TyClGroup pass -> [LRoleAnnotDecl pass]
group_roles  = [LRoleAnnotDecl GhcRn]
roles
                       , group_kisigs :: forall pass. TyClGroup pass -> [LStandaloneKindSig pass]
group_kisigs = [LStandaloneKindSig GhcRn]
kisigs
                       , group_instds :: forall pass. TyClGroup pass -> [LInstDecl pass]
group_instds = [LInstDecl GhcRn]
instds })
  = do { let role_annots :: RoleAnnotEnv
role_annots = [LRoleAnnotDecl GhcRn] -> RoleAnnotEnv
mkRoleAnnotEnv [LRoleAnnotDecl GhcRn]
roles

           -- Step 1: Typecheck the standalone kind signatures and type/class declarations
       ; String -> SDoc -> TcRn ()
traceTc String
"---- tcTyClGroup ---- {" SDoc
empty
       ; String -> SDoc -> TcRn ()
traceTc String
"Decls for" ([Name] -> SDoc
forall a. Outputable a => a -> SDoc
ppr ((LTyClDecl GhcRn -> Name) -> [LTyClDecl GhcRn] -> [Name]
forall a b. (a -> b) -> [a] -> [b]
map (TyClDecl GhcRn -> Name
forall (p :: Pass). TyClDecl (GhcPass p) -> IdP (GhcPass p)
tcdName (TyClDecl GhcRn -> Name)
-> (LTyClDecl GhcRn -> TyClDecl GhcRn) -> LTyClDecl GhcRn -> Name
forall b c a. (b -> c) -> (a -> b) -> a -> c
. LTyClDecl GhcRn -> TyClDecl GhcRn
forall l e. GenLocated l e -> e
unLoc) [LTyClDecl GhcRn]
tyclds))
       ; ([TyCon]
tyclss, [DerivInfo]
data_deriv_info) <-
           TcTypeEnv
-> TcM ([TyCon], [DerivInfo]) -> TcM ([TyCon], [DerivInfo])
forall r. TcTypeEnv -> TcM r -> TcM r
tcExtendKindEnv ([LTyClDecl GhcRn] -> TcTypeEnv
mkPromotionErrorEnv [LTyClDecl GhcRn]
tyclds) (TcM ([TyCon], [DerivInfo]) -> TcM ([TyCon], [DerivInfo]))
-> TcM ([TyCon], [DerivInfo]) -> TcM ([TyCon], [DerivInfo])
forall a b. (a -> b) -> a -> b
$ -- See Note [Type environment evolution]
           do { NameEnv Type
kisig_env <- [(Name, Type)] -> NameEnv Type
forall a. [(Name, a)] -> NameEnv a
mkNameEnv ([(Name, Type)] -> NameEnv Type)
-> IOEnv (Env TcGblEnv TcLclEnv) [(Name, Type)]
-> IOEnv (Env TcGblEnv TcLclEnv) (NameEnv Type)
forall (f :: * -> *) a b. Functor f => (a -> b) -> f a -> f b
<$> (LStandaloneKindSig GhcRn
 -> IOEnv (Env TcGblEnv TcLclEnv) (Name, Type))
-> [LStandaloneKindSig GhcRn]
-> IOEnv (Env TcGblEnv TcLclEnv) [(Name, Type)]
forall (t :: * -> *) (f :: * -> *) a b.
(Traversable t, Applicative f) =>
(a -> f b) -> t a -> f (t b)
traverse LStandaloneKindSig GhcRn
-> IOEnv (Env TcGblEnv TcLclEnv) (Name, Type)
tcStandaloneKindSig [LStandaloneKindSig GhcRn]
kisigs
              ; [LTyClDecl GhcRn]
-> NameEnv Type -> RoleAnnotEnv -> TcM ([TyCon], [DerivInfo])
tcTyClDecls [LTyClDecl GhcRn]
tyclds NameEnv Type
kisig_env RoleAnnotEnv
role_annots }

           -- Step 1.5: Make sure we don't have any type synonym cycles
       ; String -> SDoc -> TcRn ()
traceTc String
"Starting synonym cycle check" ([TyCon] -> SDoc
forall a. Outputable a => a -> SDoc
ppr [TyCon]
tyclss)
       ; Unit
this_uid <- (DynFlags -> Unit)
-> IOEnv (Env TcGblEnv TcLclEnv) DynFlags
-> IOEnv (Env TcGblEnv TcLclEnv) Unit
forall (f :: * -> *) a b. Functor f => (a -> b) -> f a -> f b
fmap DynFlags -> Unit
homeUnit IOEnv (Env TcGblEnv TcLclEnv) DynFlags
forall (m :: * -> *). HasDynFlags m => m DynFlags
getDynFlags
       ; Unit -> [TyCon] -> [LTyClDecl GhcRn] -> TcRn ()
checkSynCycles Unit
this_uid [TyCon]
tyclss [LTyClDecl GhcRn]
tyclds
       ; String -> SDoc -> TcRn ()
traceTc String
"Done synonym cycle check" ([TyCon] -> SDoc
forall a. Outputable a => a -> SDoc
ppr [TyCon]
tyclss)

           -- Step 2: Perform the validity check on those types/classes
           -- We can do this now because we are done with the recursive knot
           -- Do it before Step 3 (adding implicit things) because the latter
           -- expects well-formed TyCons
       ; String -> SDoc -> TcRn ()
traceTc String
"Starting validity check" ([TyCon] -> SDoc
forall a. Outputable a => a -> SDoc
ppr [TyCon]
tyclss)
       ; [TyCon]
tyclss <- (TyCon -> IOEnv (Env TcGblEnv TcLclEnv) [TyCon])
-> [TyCon] -> IOEnv (Env TcGblEnv TcLclEnv) [TyCon]
forall (m :: * -> *) a b. Monad m => (a -> m [b]) -> [a] -> m [b]
concatMapM TyCon -> IOEnv (Env TcGblEnv TcLclEnv) [TyCon]
checkValidTyCl [TyCon]
tyclss
       ; String -> SDoc -> TcRn ()
traceTc String
"Done validity check" ([TyCon] -> SDoc
forall a. Outputable a => a -> SDoc
ppr [TyCon]
tyclss)
       ; (TyCon -> TcRn ()) -> [TyCon] -> TcRn ()
forall (t :: * -> *) (m :: * -> *) a b.
(Foldable t, Monad m) =>
(a -> m b) -> t a -> m ()
mapM_ (TcRn () -> TcRn () -> TcRn ()
forall r. TcRn r -> TcRn r -> TcRn r
recoverM (() -> TcRn ()
forall (m :: * -> *) a. Monad m => a -> m a
return ()) (TcRn () -> TcRn ()) -> (TyCon -> TcRn ()) -> TyCon -> TcRn ()
forall b c a. (b -> c) -> (a -> b) -> a -> c
. RoleAnnotEnv -> TyCon -> TcRn ()
checkValidRoleAnnots RoleAnnotEnv
role_annots) [TyCon]
tyclss
           -- See Note [Check role annotations in a second pass]

       ; String -> SDoc -> TcRn ()
traceTc String
"---- end tcTyClGroup ---- }" SDoc
empty

           -- Step 3: Add the implicit things;
           -- we want them in the environment because
           -- they may be mentioned in interface files
       ; TcGblEnv
gbl_env <- [TyCon] -> TcRnIf TcGblEnv TcLclEnv TcGblEnv
addTyConsToGblEnv [TyCon]
tyclss

           -- Step 4: check instance declarations
       ; (TcGblEnv
gbl_env', [InstInfo GhcRn]
inst_info, [DerivInfo]
datafam_deriv_info) <-
         TcGblEnv
-> TcM (TcGblEnv, [InstInfo GhcRn], [DerivInfo])
-> TcM (TcGblEnv, [InstInfo GhcRn], [DerivInfo])
forall gbl lcl a. gbl -> TcRnIf gbl lcl a -> TcRnIf gbl lcl a
setGblEnv TcGblEnv
gbl_env (TcM (TcGblEnv, [InstInfo GhcRn], [DerivInfo])
 -> TcM (TcGblEnv, [InstInfo GhcRn], [DerivInfo]))
-> TcM (TcGblEnv, [InstInfo GhcRn], [DerivInfo])
-> TcM (TcGblEnv, [InstInfo GhcRn], [DerivInfo])
forall a b. (a -> b) -> a -> b
$
         [LInstDecl GhcRn] -> TcM (TcGblEnv, [InstInfo GhcRn], [DerivInfo])
tcInstDecls1 [LInstDecl GhcRn]
instds

       ; let deriv_info :: [DerivInfo]
deriv_info = [DerivInfo]
datafam_deriv_info [DerivInfo] -> [DerivInfo] -> [DerivInfo]
forall a. [a] -> [a] -> [a]
++ [DerivInfo]
data_deriv_info
       ; (TcGblEnv, [InstInfo GhcRn], [DerivInfo])
-> TcM (TcGblEnv, [InstInfo GhcRn], [DerivInfo])
forall (m :: * -> *) a. Monad m => a -> m a
return (TcGblEnv
gbl_env', [InstInfo GhcRn]
inst_info, [DerivInfo]
deriv_info) }

-- Gives the kind for every TyCon that has a standalone kind signature
type KindSigEnv = NameEnv Kind

tcTyClDecls
  :: [LTyClDecl GhcRn]
  -> KindSigEnv
  -> RoleAnnotEnv
  -> TcM ([TyCon], [DerivInfo])
tcTyClDecls :: [LTyClDecl GhcRn]
-> NameEnv Type -> RoleAnnotEnv -> TcM ([TyCon], [DerivInfo])
tcTyClDecls [LTyClDecl GhcRn]
tyclds NameEnv Type
kisig_env RoleAnnotEnv
role_annots
  = do {    -- Step 1: kind-check this group and returns the final
            -- (possibly-polymorphic) kind of each TyCon and Class
            -- See Note [Kind checking for type and class decls]
         [TyCon]
tc_tycons <- NameEnv Type
-> [LTyClDecl GhcRn] -> IOEnv (Env TcGblEnv TcLclEnv) [TyCon]
kcTyClGroup NameEnv Type
kisig_env [LTyClDecl GhcRn]
tyclds
       ; String -> SDoc -> TcRn ()
traceTc String
"tcTyAndCl generalized kinds" ([SDoc] -> SDoc
vcat ((TyCon -> SDoc) -> [TyCon] -> [SDoc]
forall a b. (a -> b) -> [a] -> [b]
map TyCon -> SDoc
ppr_tc_tycon [TyCon]
tc_tycons))

            -- Step 2: type-check all groups together, returning
            -- the final TyCons and Classes
            --
            -- NB: We have to be careful here to NOT eagerly unfold
            -- type synonyms, as we have not tested for type synonym
            -- loops yet and could fall into a black hole.
       ; (([TyCon], [DerivInfo]) -> TcM ([TyCon], [DerivInfo]))
-> TcM ([TyCon], [DerivInfo])
forall a env. (a -> IOEnv env a) -> IOEnv env a
fixM ((([TyCon], [DerivInfo]) -> TcM ([TyCon], [DerivInfo]))
 -> TcM ([TyCon], [DerivInfo]))
-> (([TyCon], [DerivInfo]) -> TcM ([TyCon], [DerivInfo]))
-> TcM ([TyCon], [DerivInfo])
forall a b. (a -> b) -> a -> b
$ \ ~([TyCon]
rec_tyclss, [DerivInfo]
_) -> do
           { TcGblEnv
tcg_env <- TcRnIf TcGblEnv TcLclEnv TcGblEnv
forall gbl lcl. TcRnIf gbl lcl gbl
getGblEnv
           ; let roles :: Name -> [Role]
roles = HscSource -> RoleAnnotEnv -> [TyCon] -> Name -> [Role]
inferRoles (TcGblEnv -> HscSource
tcg_src TcGblEnv
tcg_env) RoleAnnotEnv
role_annots [TyCon]
rec_tyclss

                 -- Populate environment with knot-tied ATyCon for TyCons
                 -- NB: if the decls mention any ill-staged data cons
                 -- (see Note [Recursion and promoting data constructors])
                 -- we will have failed already in kcTyClGroup, so no worries here
           ; ([TyCon]
tycons, [[DerivInfo]]
data_deriv_infos) <-
             [(Name, TyThing)]
-> TcM ([TyCon], [[DerivInfo]]) -> TcM ([TyCon], [[DerivInfo]])
forall r. [(Name, TyThing)] -> TcM r -> TcM r
tcExtendRecEnv ([TyCon] -> [TyCon] -> [(Name, TyThing)]
zipRecTyClss [TyCon]
tc_tycons [TyCon]
rec_tyclss) (TcM ([TyCon], [[DerivInfo]]) -> TcM ([TyCon], [[DerivInfo]]))
-> TcM ([TyCon], [[DerivInfo]]) -> TcM ([TyCon], [[DerivInfo]])
forall a b. (a -> b) -> a -> b
$

                 -- Also extend the local type envt with bindings giving
                 -- a TcTyCon for each knot-tied TyCon or Class
                 -- See Note [Type checking recursive type and class declarations]
                 -- and Note [Type environment evolution]
             [TyCon]
-> TcM ([TyCon], [[DerivInfo]]) -> TcM ([TyCon], [[DerivInfo]])
forall a. [TyCon] -> TcM a -> TcM a
tcExtendKindEnvWithTyCons [TyCon]
tc_tycons (TcM ([TyCon], [[DerivInfo]]) -> TcM ([TyCon], [[DerivInfo]]))
-> TcM ([TyCon], [[DerivInfo]]) -> TcM ([TyCon], [[DerivInfo]])
forall a b. (a -> b) -> a -> b
$

                 -- Kind and type check declarations for this group
               (LTyClDecl GhcRn
 -> IOEnv (Env TcGblEnv TcLclEnv) (TyCon, [DerivInfo]))
-> [LTyClDecl GhcRn] -> TcM ([TyCon], [[DerivInfo]])
forall (m :: * -> *) a b c.
Applicative m =>
(a -> m (b, c)) -> [a] -> m ([b], [c])
mapAndUnzipM ((Name -> [Role])
-> LTyClDecl GhcRn
-> IOEnv (Env TcGblEnv TcLclEnv) (TyCon, [DerivInfo])
tcTyClDecl Name -> [Role]
roles) [LTyClDecl GhcRn]
tyclds
           ; ([TyCon], [DerivInfo]) -> TcM ([TyCon], [DerivInfo])
forall (m :: * -> *) a. Monad m => a -> m a
return ([TyCon]
tycons, [[DerivInfo]] -> [DerivInfo]
forall (t :: * -> *) a. Foldable t => t [a] -> [a]
concat [[DerivInfo]]
data_deriv_infos)
           } }
  where
    ppr_tc_tycon :: TyCon -> SDoc
ppr_tc_tycon TyCon
tc = SDoc -> SDoc
parens ([SDoc] -> SDoc
sep [ Name -> SDoc
forall a. Outputable a => a -> SDoc
ppr (TyCon -> Name
tyConName TyCon
tc) SDoc -> SDoc -> SDoc
<> SDoc
comma
                                  , [TyConBinder] -> SDoc
forall a. Outputable a => a -> SDoc
ppr (TyCon -> [TyConBinder]
tyConBinders TyCon
tc) SDoc -> SDoc -> SDoc
<> SDoc
comma
                                  , Type -> SDoc
forall a. Outputable a => a -> SDoc
ppr (TyCon -> Type
tyConResKind TyCon
tc)
                                  , Bool -> SDoc
forall a. Outputable a => a -> SDoc
ppr (TyCon -> Bool
isTcTyCon TyCon
tc) ])

zipRecTyClss :: [TcTyCon]
             -> [TyCon]           -- Knot-tied
             -> [(Name,TyThing)]
-- Build a name-TyThing mapping for the TyCons bound by decls
-- being careful not to look at the knot-tied [TyThing]
-- The TyThings in the result list must have a visible ATyCon,
-- because typechecking types (in, say, tcTyClDecl) looks at
-- this outer constructor
zipRecTyClss :: [TyCon] -> [TyCon] -> [(Name, TyThing)]
zipRecTyClss [TyCon]
tc_tycons [TyCon]
rec_tycons
  = [ (Name
name, TyCon -> TyThing
ATyCon (Name -> TyCon
get Name
name)) | TyCon
tc_tycon <- [TyCon]
tc_tycons, let name :: Name
name = TyCon -> Name
forall a. NamedThing a => a -> Name
getName TyCon
tc_tycon ]
  where
    rec_tc_env :: NameEnv TyCon
    rec_tc_env :: NameEnv TyCon
rec_tc_env = (TyCon -> NameEnv TyCon -> NameEnv TyCon)
-> NameEnv TyCon -> [TyCon] -> NameEnv TyCon
forall (t :: * -> *) a b.
Foldable t =>
(a -> b -> b) -> b -> t a -> b
foldr TyCon -> NameEnv TyCon -> NameEnv TyCon
add_tc NameEnv TyCon
forall a. NameEnv a
emptyNameEnv [TyCon]
rec_tycons

    add_tc :: TyCon -> NameEnv TyCon -> NameEnv TyCon
    add_tc :: TyCon -> NameEnv TyCon -> NameEnv TyCon
add_tc TyCon
tc NameEnv TyCon
env = (TyCon -> NameEnv TyCon -> NameEnv TyCon)
-> NameEnv TyCon -> [TyCon] -> NameEnv TyCon
forall (t :: * -> *) a b.
Foldable t =>
(a -> b -> b) -> b -> t a -> b
foldr TyCon -> NameEnv TyCon -> NameEnv TyCon
add_one_tc NameEnv TyCon
env (TyCon
tc TyCon -> [TyCon] -> [TyCon]
forall a. a -> [a] -> [a]
: TyCon -> [TyCon]
tyConATs TyCon
tc)

    add_one_tc :: TyCon -> NameEnv TyCon -> NameEnv TyCon
    add_one_tc :: TyCon -> NameEnv TyCon -> NameEnv TyCon
add_one_tc TyCon
tc NameEnv TyCon
env = NameEnv TyCon -> Name -> TyCon -> NameEnv TyCon
forall a. NameEnv a -> Name -> a -> NameEnv a
extendNameEnv NameEnv TyCon
env (TyCon -> Name
tyConName TyCon
tc) TyCon
tc

    get :: Name -> TyCon
get Name
name = case NameEnv TyCon -> Name -> Maybe TyCon
forall a. NameEnv a -> Name -> Maybe a
lookupNameEnv NameEnv TyCon
rec_tc_env Name
name of
                 Just TyCon
tc -> TyCon
tc
                 Maybe TyCon
other   -> String -> SDoc -> TyCon
forall a. HasCallStack => String -> SDoc -> a
pprPanic String
"zipRecTyClss" (Name -> SDoc
forall a. Outputable a => a -> SDoc
ppr Name
name SDoc -> SDoc -> SDoc
<+> Maybe TyCon -> SDoc
forall a. Outputable a => a -> SDoc
ppr Maybe TyCon
other)

{-
************************************************************************
*                                                                      *
                Kind checking
*                                                                      *
************************************************************************

Note [Kind checking for type and class decls]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Kind checking is done thus:

   1. Make up a kind variable for each parameter of the declarations,
      and extend the kind environment (which is in the TcLclEnv)

   2. Kind check the declarations

We need to kind check all types in the mutually recursive group
before we know the kind of the type variables.  For example:

  class C a where
     op :: D b => a -> b -> b

  class D c where
     bop :: (Monad c) => ...

Here, the kind of the locally-polymorphic type variable "b"
depends on *all the uses of class D*.  For example, the use of
Monad c in bop's type signature means that D must have kind Type->Type.

Note: we don't treat type synonyms specially (we used to, in the past);
in particular, even if we have a type synonym cycle, we still kind check
it normally, and test for cycles later (checkSynCycles).  The reason
we can get away with this is because we have more systematic TYPE r
inference, which means that we can do unification between kinds that
aren't lifted (this historically was not true.)

The downside of not directly reading off the kinds of the RHS of
type synonyms in topological order is that we don't transparently
support making synonyms of types with higher-rank kinds.  But
you can always specify a CUSK directly to make this work out.
See tc269 for an example.

Note [CUSKs and PolyKinds]
~~~~~~~~~~~~~~~~~~~~~~~~~~
Consider

    data T (a :: *) = MkT (S a)   -- Has CUSK
    data S a = MkS (T Int) (S a)  -- No CUSK

Via inferInitialKinds we get
  T :: * -> *
  S :: kappa -> *

Then we call kcTyClDecl on each decl in the group, to constrain the
kind unification variables.  BUT we /skip/ the RHS of any decl with
a CUSK.  Here we skip the RHS of T, so we eventually get
  S :: forall k. k -> *

This gets us more polymorphism than we would otherwise get, similar
(but implemented strangely differently from) the treatment of type
signatures in value declarations.

However, we only want to do so when we have PolyKinds.
When we have NoPolyKinds, we don't skip those decls, because we have defaulting
(#16609). Skipping won't bring us more polymorphism when we have defaulting.
Consider

  data T1 a = MkT1 T2        -- No CUSK
  data T2 = MkT2 (T1 Maybe)  -- Has CUSK

If we skip the rhs of T2 during kind-checking, the kind of a remains unsolved.
With PolyKinds, we do generalization to get T1 :: forall a. a -> *. And the
program type-checks.
But with NoPolyKinds, we do defaulting to get T1 :: * -> *. Defaulting happens
in quantifyTyVars, which is called from generaliseTcTyCon. Then type-checking
(T1 Maybe) will throw a type error.

Summary: with PolyKinds, we must skip; with NoPolyKinds, we must /not/ skip.

Open type families
~~~~~~~~~~~~~~~~~~
This treatment of type synonyms only applies to Haskell 98-style synonyms.
General type functions can be recursive, and hence, appear in `alg_decls'.

The kind of an open type family is solely determinded by its kind signature;
hence, only kind signatures participate in the construction of the initial
kind environment (as constructed by `inferInitialKind'). In fact, we ignore
instances of families altogether in the following. However, we need to include
the kinds of *associated* families into the construction of the initial kind
environment. (This is handled by `allDecls').

See also Note [Kind checking recursive type and class declarations]

Note [How TcTyCons work]
~~~~~~~~~~~~~~~~~~~~~~~~
TcTyCons are used for two distinct purposes

1.  When recovering from a type error in a type declaration,
    we want to put the erroneous TyCon in the environment in a
    way that won't lead to more errors.  We use a TcTyCon for this;
    see makeRecoveryTyCon.

2.  When checking a type/class declaration (in module GHC.Tc.TyCl), we come
    upon knowledge of the eventual tycon in bits and pieces.

      S1) First, we use inferInitialKinds to look over the user-provided
          kind signature of a tycon (including, for example, the number
          of parameters written to the tycon) to get an initial shape of
          the tycon's kind.  We record that shape in a TcTyCon.

          For CUSK tycons, the TcTyCon has the final, generalised kind.
          For non-CUSK tycons, the TcTyCon has as its tyConBinders only
          the explicit arguments given -- no kind variables, etc.

      S2) Then, using these initial kinds, we kind-check the body of the
          tycon (class methods, data constructors, etc.), filling in the
          metavariables in the tycon's initial kind.

      S3) We then generalize to get the (non-CUSK) tycon's final, fixed
          kind. Finally, once this has happened for all tycons in a
          mutually recursive group, we can desugar the lot.

    For convenience, we store partially-known tycons in TcTyCons, which
    might store meta-variables. These TcTyCons are stored in the local
    environment in GHC.Tc.TyCl, until the real full TyCons can be created
    during desugaring. A desugared program should never have a TcTyCon.

3.  In a TcTyCon, everything is zonked after the kind-checking pass (S2).

4.  tyConScopedTyVars.  A challenging piece in all of this is that we
    end up taking three separate passes over every declaration:
      - one in inferInitialKind (this pass look only at the head, not the body)
      - one in kcTyClDecls (to kind-check the body)
      - a final one in tcTyClDecls (to desugar)

    In the latter two passes, we need to connect the user-written type
    variables in an LHsQTyVars with the variables in the tycon's
    inferred kind. Because the tycon might not have a CUSK, this
    matching up is, in general, quite hard to do.  (Look through the
    git history between Dec 2015 and Apr 2016 for
    GHC.Tc.Gen.HsType.splitTelescopeTvs!)

    Instead of trying, we just store the list of type variables to
    bring into scope, in the tyConScopedTyVars field of the TcTyCon.
    These tyvars are brought into scope in GHC.Tc.Gen.HsType.bindTyClTyVars.

    In a TcTyCon, why is tyConScopedTyVars :: [(Name,TcTyVar)] rather
    than just [TcTyVar]?  Consider these mutually-recursive decls
       data T (a :: k1) b = MkT (S a b)
       data S (c :: k2) d = MkS (T c d)
    We start with k1 bound to kappa1, and k2 to kappa2; so initially
    in the (Name,TcTyVar) pairs the Name is that of the TcTyVar. But
    then kappa1 and kappa2 get unified; so after the zonking in
    'generalise' in 'kcTyClGroup' the Name and TcTyVar may differ.

See also Note [Type checking recursive type and class declarations].

Note [Swizzling the tyvars before generaliseTcTyCon]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
This Note only applies when /inferring/ the kind of a TyCon.
If there is a separate kind signature, or a CUSK, we take an entirely
different code path.

For inference, consider
   class C (f :: k) x where
      type T f
      op :: D f => blah
   class D (g :: j) y where
      op :: C g => y -> blah

Here C and D are considered mutually recursive.  Neither has a CUSK.
Just before generalisation we have the (un-quantified) kinds
   C :: k1 -> k2 -> Constraint
   T :: k1 -> Type
   D :: k1 -> Type -> Constraint
Notice that f's kind and g's kind have been unified to 'k1'. We say
that k1 is the "representative" of k in C's decl, and of j in D's decl.

Now when quantifying, we'd like to end up with
   C :: forall {k2}. forall k. k -> k2 -> Constraint
   T :: forall k. k -> Type
   D :: forall j. j -> Type -> Constraint

That is, we want to swizzle the representative to have the Name given
by the user. Partly this is to improve error messages and the output of
:info in GHCi.  But it is /also/ important because the code for a
default method may mention the class variable(s), but at that point
(tcClassDecl2), we only have the final class tyvars available.
(Alternatively, we could record the scoped type variables in the
TyCon, but it's a nuisance to do so.)

Notes:

* On the input to generaliseTyClDecl, the mapping between the
  user-specified Name and the representative TyVar is recorded in the
  tyConScopedTyVars of the TcTyCon.  NB: you first need to zonk to see
  this representative TyVar.

* The swizzling is actually performed by swizzleTcTyConBndrs

* We must do the swizzling across the whole class decl. Consider
     class C f where
       type S (f :: k)
       type T f
  Here f's kind k is a parameter of C, and its identity is shared
  with S and T.  So if we swizzle the representative k at all, we
  must do so consistently for the entire declaration.

  Hence the call to check_duplicate_tc_binders is in generaliseTyClDecl,
  rather than in generaliseTcTyCon.

There are errors to catch here.  Suppose we had
   class E (f :: j) (g :: k) where
     op :: SameKind f g -> blah

Then, just before generalisation we will have the (unquantified)
   E :: k1 -> k1 -> Constraint

That's bad!  Two distinctly-named tyvars (j and k) have ended up with
the same representative k1.  So when swizzling, we check (in
check_duplicate_tc_binders) that two distinct source names map
to the same representative.

Here's an interesting case:
    class C1 f where
      type S (f :: k1)
      type T (f :: k2)
Here k1 and k2 are different Names, but they end up mapped to the
same representative TyVar.  To make the swizzling consistent (remember
we must have a single k across C1, S and T) we reject the program.

Another interesting case
    class C2 f where
      type S (f :: k) (p::Type)
      type T (f :: k) (p::Type->Type)

Here the two k's (and the two p's) get distinct Uniques, because they
are seen by the renamer as locally bound in S and T resp.  But again
the two (distinct) k's end up bound to the same representative TyVar.
You might argue that this should be accepted, but it's definitely
rejected (via an entirely different code path) if you add a kind sig:
    type C2' :: j -> Constraint
    class C2' f where
      type S (f :: k) (p::Type)
We get
    • Expected kind ‘j’, but ‘f’ has kind ‘k’
    • In the associated type family declaration for ‘S’

So we reject C2 too, even without the kind signature.  We have
to do a bit of work to get a good error message, since both k's
look the same to the user.

Another case
    class C3 (f :: k1) where
      type S (f :: k2)

This will be rejected too.


Note [Type environment evolution]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
As we typecheck a group of declarations the type environment evolves.
Consider for example:
  data B (a :: Type) = MkB (Proxy 'MkB)

We do the following steps:

  1. Start of tcTyClDecls: use mkPromotionErrorEnv to initialise the
     type env with promotion errors
            B   :-> TyConPE
            MkB :-> DataConPE

  2. kcTyCLGroup
      - Do inferInitialKinds, which will signal a promotion
        error if B is used in any of the kinds needed to initialise
        B's kind (e.g. (a :: Type)) here

      - Extend the type env with these initial kinds (monomorphic for
        decls that lack a CUSK)
            B :-> TcTyCon <initial kind>
        (thereby overriding the B :-> TyConPE binding)
        and do kcLTyClDecl on each decl to get equality constraints on
        all those initial kinds

      - Generalise the initial kind, making a poly-kinded TcTyCon

  3. Back in tcTyDecls, extend the envt with bindings of the poly-kinded
     TcTyCons, again overriding the promotion-error bindings.

     But note that the data constructor promotion errors are still in place
     so that (in our example) a use of MkB will still be signalled as
     an error.

  4. Typecheck the decls.

  5. In tcTyClGroup, extend the envt with bindings for TyCon and DataCons


Note [Missed opportunity to retain higher-rank kinds]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
In 'kcTyClGroup', there is a missed opportunity to make kind
inference work in a few more cases.  The idea is analogous
to Note [Single function non-recursive binding special-case]:

     * If we have an SCC with a single decl, which is non-recursive,
       instead of creating a unification variable representing the
       kind of the decl and unifying it with the rhs, we can just
       read the type directly of the rhs.

     * Furthermore, we can update our SCC analysis to ignore
       dependencies on declarations which have CUSKs: we don't
       have to kind-check these all at once, since we can use
       the CUSK to initialize the kind environment.

Unfortunately this requires reworking a bit of the code in
'kcLTyClDecl' so I've decided to punt unless someone shouts about it.

Note [Don't process associated types in getInitialKind]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Previously, we processed associated types in the thing_inside in getInitialKind,
but this was wrong -- we want to do ATs sepearately.
The consequence for not doing it this way is #15142:

  class ListTuple (tuple :: Type) (as :: [(k, Type)]) where
    type ListToTuple as :: Type

We assign k a kind kappa[1]. When checking the tuple (k, Type), we try to unify
kappa ~ Type, but this gets deferred because we bumped the TcLevel as we bring
`tuple` into scope. Thus, when we check ListToTuple, kappa[1] still hasn't
unified with Type. And then, when we generalize the kind of ListToTuple (which
indeed has a CUSK, according to the rules), we skolemize the free metavariable
kappa. Note that we wouldn't skolemize kappa when generalizing the kind of ListTuple,
because the solveEqualities in kcInferDeclHeader is at TcLevel 1 and so kappa[1]
will unify with Type.

Bottom line: as associated types should have no effect on a CUSK enclosing class,
we move processing them to a separate action, run after the outer kind has
been generalized.

-}

kcTyClGroup :: KindSigEnv -> [LTyClDecl GhcRn] -> TcM [TcTyCon]

-- Kind check this group, kind generalize, and return the resulting local env
-- This binds the TyCons and Classes of the group, but not the DataCons
-- See Note [Kind checking for type and class decls]
-- and Note [Inferring kinds for type declarations]
kcTyClGroup :: NameEnv Type
-> [LTyClDecl GhcRn] -> IOEnv (Env TcGblEnv TcLclEnv) [TyCon]
kcTyClGroup NameEnv Type
kisig_env [LTyClDecl GhcRn]
decls
  = do  { Module
mod <- IOEnv (Env TcGblEnv TcLclEnv) Module
forall (m :: * -> *). HasModule m => m Module
getModule
        ; String -> SDoc -> TcRn ()
traceTc String
"---- kcTyClGroup ---- {"
                  (String -> SDoc
text String
"module" SDoc -> SDoc -> SDoc
<+> Module -> SDoc
forall a. Outputable a => a -> SDoc
ppr Module
mod SDoc -> SDoc -> SDoc
$$ [SDoc] -> SDoc
vcat ((LTyClDecl GhcRn -> SDoc) -> [LTyClDecl GhcRn] -> [SDoc]
forall a b. (a -> b) -> [a] -> [b]
map LTyClDecl GhcRn -> SDoc
forall a. Outputable a => a -> SDoc
ppr [LTyClDecl GhcRn]
decls))

          -- Kind checking;
          --    1. Bind kind variables for decls
          --    2. Kind-check decls
          --    3. Generalise the inferred kinds
          -- See Note [Kind checking for type and class decls]

        ; Bool
cusks_enabled <- Extension -> TcRnIf TcGblEnv TcLclEnv Bool
forall gbl lcl. Extension -> TcRnIf gbl lcl Bool
xoptM Extension
LangExt.CUSKs TcRnIf TcGblEnv TcLclEnv Bool
-> TcRnIf TcGblEnv TcLclEnv Bool -> TcRnIf TcGblEnv TcLclEnv Bool
forall (f :: * -> *). Applicative f => f Bool -> f Bool -> f Bool
<&&> Extension -> TcRnIf TcGblEnv TcLclEnv Bool
forall gbl lcl. Extension -> TcRnIf gbl lcl Bool
xoptM Extension
LangExt.PolyKinds
                    -- See Note [CUSKs and PolyKinds]
        ; let ([LTyClDecl GhcRn]
kindless_decls, [(LTyClDecl GhcRn, SAKS_or_CUSK)]
kinded_decls) = (LTyClDecl GhcRn
 -> Either (LTyClDecl GhcRn) (LTyClDecl GhcRn, SAKS_or_CUSK))
-> [LTyClDecl GhcRn]
-> ([LTyClDecl GhcRn], [(LTyClDecl GhcRn, SAKS_or_CUSK)])
forall a b c. (a -> Either b c) -> [a] -> ([b], [c])
partitionWith LTyClDecl GhcRn
-> Either (LTyClDecl GhcRn) (LTyClDecl GhcRn, SAKS_or_CUSK)
get_kind [LTyClDecl GhcRn]
decls

              get_kind :: LTyClDecl GhcRn
-> Either (LTyClDecl GhcRn) (LTyClDecl GhcRn, SAKS_or_CUSK)
get_kind LTyClDecl GhcRn
d
                | Just Type
ki <- NameEnv Type -> Name -> Maybe Type
forall a. NameEnv a -> Name -> Maybe a
lookupNameEnv NameEnv Type
kisig_env (TyClDecl GhcRn -> IdP GhcRn
forall (p :: Pass). TyClDecl (GhcPass p) -> IdP (GhcPass p)
tcdName (LTyClDecl GhcRn -> TyClDecl GhcRn
forall l e. GenLocated l e -> e
unLoc LTyClDecl GhcRn
d))
                = (LTyClDecl GhcRn, SAKS_or_CUSK)
-> Either (LTyClDecl GhcRn) (LTyClDecl GhcRn, SAKS_or_CUSK)
forall a b. b -> Either a b
Right (LTyClDecl GhcRn
d, Type -> SAKS_or_CUSK
SAKS Type
ki)

                | Bool
cusks_enabled Bool -> Bool -> Bool
&& TyClDecl GhcRn -> Bool
hsDeclHasCusk (LTyClDecl GhcRn -> TyClDecl GhcRn
forall l e. GenLocated l e -> e
unLoc LTyClDecl GhcRn
d)
                = (LTyClDecl GhcRn, SAKS_or_CUSK)
-> Either (LTyClDecl GhcRn) (LTyClDecl GhcRn, SAKS_or_CUSK)
forall a b. b -> Either a b
Right (LTyClDecl GhcRn
d, SAKS_or_CUSK
CUSK)

                | Bool
otherwise = LTyClDecl GhcRn
-> Either (LTyClDecl GhcRn) (LTyClDecl GhcRn, SAKS_or_CUSK)
forall a b. a -> Either a b
Left LTyClDecl GhcRn
d

        ; [TyCon]
checked_tcs <- [(LTyClDecl GhcRn, SAKS_or_CUSK)]
-> IOEnv (Env TcGblEnv TcLclEnv) [TyCon]
checkInitialKinds [(LTyClDecl GhcRn, SAKS_or_CUSK)]
kinded_decls
        ; [TyCon]
inferred_tcs
            <- [TyCon]
-> IOEnv (Env TcGblEnv TcLclEnv) [TyCon]
-> IOEnv (Env TcGblEnv TcLclEnv) [TyCon]
forall a. [TyCon] -> TcM a -> TcM a
tcExtendKindEnvWithTyCons [TyCon]
checked_tcs (IOEnv (Env TcGblEnv TcLclEnv) [TyCon]
 -> IOEnv (Env TcGblEnv TcLclEnv) [TyCon])
-> IOEnv (Env TcGblEnv TcLclEnv) [TyCon]
-> IOEnv (Env TcGblEnv TcLclEnv) [TyCon]
forall a b. (a -> b) -> a -> b
$
               IOEnv (Env TcGblEnv TcLclEnv) [TyCon]
-> IOEnv (Env TcGblEnv TcLclEnv) [TyCon]
forall r. TcM r -> TcM r
pushTcLevelM_   (IOEnv (Env TcGblEnv TcLclEnv) [TyCon]
 -> IOEnv (Env TcGblEnv TcLclEnv) [TyCon])
-> IOEnv (Env TcGblEnv TcLclEnv) [TyCon]
-> IOEnv (Env TcGblEnv TcLclEnv) [TyCon]
forall a b. (a -> b) -> a -> b
$  -- We are going to kind-generalise, so
                                  -- unification variables in here must
                                  -- be one level in
               IOEnv (Env TcGblEnv TcLclEnv) [TyCon]
-> IOEnv (Env TcGblEnv TcLclEnv) [TyCon]
forall r. TcM r -> TcM r
solveEqualities (IOEnv (Env TcGblEnv TcLclEnv) [TyCon]
 -> IOEnv (Env TcGblEnv TcLclEnv) [TyCon])
-> IOEnv (Env TcGblEnv TcLclEnv) [TyCon]
-> IOEnv (Env TcGblEnv TcLclEnv) [TyCon]
forall a b. (a -> b) -> a -> b
$
               do {  -- Step 1: Bind kind variables for all decls
                    [TyCon]
mono_tcs <- [LTyClDecl GhcRn] -> IOEnv (Env TcGblEnv TcLclEnv) [TyCon]
inferInitialKinds [LTyClDecl GhcRn]
kindless_decls

                  ; String -> SDoc -> TcRn ()
traceTc String
"kcTyClGroup: initial kinds" (SDoc -> TcRn ()) -> SDoc -> TcRn ()
forall a b. (a -> b) -> a -> b
$
                    [TyCon] -> SDoc
ppr_tc_kinds [TyCon]
mono_tcs

                    -- Step 2: Set extended envt, kind-check the decls
                    -- NB: the environment extension overrides the tycon
                    --     promotion-errors bindings
                    --     See Note [Type environment evolution]
                  ; [TyCon] -> TcRn () -> TcRn ()
forall a. [TyCon] -> TcM a -> TcM a
tcExtendKindEnvWithTyCons [TyCon]
mono_tcs (TcRn () -> TcRn ()) -> TcRn () -> TcRn ()
forall a b. (a -> b) -> a -> b
$
                    (LTyClDecl GhcRn -> TcRn ()) -> [LTyClDecl GhcRn] -> TcRn ()
forall (t :: * -> *) (m :: * -> *) a b.
(Foldable t, Monad m) =>
(a -> m b) -> t a -> m ()
mapM_ LTyClDecl GhcRn -> TcRn ()
kcLTyClDecl [LTyClDecl GhcRn]
kindless_decls

                  ; [TyCon] -> IOEnv (Env TcGblEnv TcLclEnv) [TyCon]
forall (m :: * -> *) a. Monad m => a -> m a
return [TyCon]
mono_tcs }

        -- Step 3: generalisation
        -- Finally, go through each tycon and give it its final kind,
        -- with all the required, specified, and inferred variables
        -- in order.
        ; let inferred_tc_env :: NameEnv TyCon
inferred_tc_env = [(Name, TyCon)] -> NameEnv TyCon
forall a. [(Name, a)] -> NameEnv a
mkNameEnv ([(Name, TyCon)] -> NameEnv TyCon)
-> [(Name, TyCon)] -> NameEnv TyCon
forall a b. (a -> b) -> a -> b
$
                                (TyCon -> (Name, TyCon)) -> [TyCon] -> [(Name, TyCon)]
forall a b. (a -> b) -> [a] -> [b]
map (\TyCon
tc -> (TyCon -> Name
tyConName TyCon
tc, TyCon
tc)) [TyCon]
inferred_tcs
        ; [TyCon]
generalized_tcs <- (LTyClDecl GhcRn -> IOEnv (Env TcGblEnv TcLclEnv) [TyCon])
-> [LTyClDecl GhcRn] -> IOEnv (Env TcGblEnv TcLclEnv) [TyCon]
forall (m :: * -> *) a b. Monad m => (a -> m [b]) -> [a] -> m [b]
concatMapM (NameEnv TyCon
-> LTyClDecl GhcRn -> IOEnv (Env TcGblEnv TcLclEnv) [TyCon]
generaliseTyClDecl NameEnv TyCon
inferred_tc_env)
                                        [LTyClDecl GhcRn]
kindless_decls

        ; let poly_tcs :: [TyCon]
poly_tcs = [TyCon]
checked_tcs [TyCon] -> [TyCon] -> [TyCon]
forall a. [a] -> [a] -> [a]
++ [TyCon]
generalized_tcs
        ; String -> SDoc -> TcRn ()
traceTc String
"---- kcTyClGroup end ---- }" ([TyCon] -> SDoc
ppr_tc_kinds [TyCon]
poly_tcs)
        ; [TyCon] -> IOEnv (Env TcGblEnv TcLclEnv) [TyCon]
forall (m :: * -> *) a. Monad m => a -> m a
return [TyCon]
poly_tcs }
  where
    ppr_tc_kinds :: [TyCon] -> SDoc
ppr_tc_kinds [TyCon]
tcs = [SDoc] -> SDoc
vcat ((TyCon -> SDoc) -> [TyCon] -> [SDoc]
forall a b. (a -> b) -> [a] -> [b]
map TyCon -> SDoc
pp_tc [TyCon]
tcs)
    pp_tc :: TyCon -> SDoc
pp_tc TyCon
tc = Name -> SDoc
forall a. Outputable a => a -> SDoc
ppr (TyCon -> Name
tyConName TyCon
tc) SDoc -> SDoc -> SDoc
<+> SDoc
dcolon SDoc -> SDoc -> SDoc
<+> Type -> SDoc
forall a. Outputable a => a -> SDoc
ppr (TyCon -> Type
tyConKind TyCon
tc)

type ScopedPairs = [(Name, TcTyVar)]
  -- The ScopedPairs for a TcTyCon are precisely
  --    specified-tvs ++ required-tvs
  -- You can distinguish them because there are tyConArity required-tvs

generaliseTyClDecl :: NameEnv TcTyCon -> LTyClDecl GhcRn -> TcM [TcTyCon]
-- See Note [Swizzling the tyvars before generaliseTcTyCon]
generaliseTyClDecl :: NameEnv TyCon
-> LTyClDecl GhcRn -> IOEnv (Env TcGblEnv TcLclEnv) [TyCon]
generaliseTyClDecl NameEnv TyCon
inferred_tc_env (L SrcSpan
_ TyClDecl GhcRn
decl)
  = do { let names_in_this_decl :: [Name]
             names_in_this_decl :: [Name]
names_in_this_decl = TyClDecl GhcRn -> [Name]
tycld_names TyClDecl GhcRn
decl

       -- Extract the specified/required binders and skolemise them
       ; [(TyCon, [(Name, TyVar)])]
tc_with_tvs  <- (Name -> IOEnv (Env TcGblEnv TcLclEnv) (TyCon, [(Name, TyVar)]))
-> [Name]
-> IOEnv (Env TcGblEnv TcLclEnv) [(TyCon, [(Name, TyVar)])]
forall (t :: * -> *) (m :: * -> *) a b.
(Traversable t, Monad m) =>
(a -> m b) -> t a -> m (t b)
mapM Name -> IOEnv (Env TcGblEnv TcLclEnv) (TyCon, [(Name, TyVar)])
skolemise_tc_tycon [Name]
names_in_this_decl

       -- Zonk, to manifest the side-effects of skolemisation to the swizzler
       -- NB: it's important to skolemise them all before this step. E.g.
       --         class C f where { type T (f :: k) }
       --     We only skolemise k when looking at T's binders,
       --     but k appears in f's kind in C's binders.
       ; [(TyCon, [(Name, TyVar)], Type)]
tc_infos <- ((TyCon, [(Name, TyVar)])
 -> IOEnv (Env TcGblEnv TcLclEnv) (TyCon, [(Name, TyVar)], Type))
-> [(TyCon, [(Name, TyVar)])]
-> IOEnv (Env TcGblEnv TcLclEnv) [(TyCon, [(Name, TyVar)], Type)]
forall (t :: * -> *) (m :: * -> *) a b.
(Traversable t, Monad m) =>
(a -> m b) -> t a -> m (t b)
mapM (TyCon, [(Name, TyVar)])
-> IOEnv (Env TcGblEnv TcLclEnv) (TyCon, [(Name, TyVar)], Type)
zonk_tc_tycon [(TyCon, [(Name, TyVar)])]
tc_with_tvs

       -- Swizzle
       ; [(TyCon, [(Name, TyVar)], Type)]
swizzled_infos <- TyClDecl GhcRn
-> IOEnv (Env TcGblEnv TcLclEnv) [(TyCon, [(Name, TyVar)], Type)]
-> IOEnv (Env TcGblEnv TcLclEnv) [(TyCon, [(Name, TyVar)], Type)]
forall a. TyClDecl GhcRn -> TcM a -> TcM a
tcAddDeclCtxt TyClDecl GhcRn
decl ([(TyCon, [(Name, TyVar)], Type)]
-> IOEnv (Env TcGblEnv TcLclEnv) [(TyCon, [(Name, TyVar)], Type)]
swizzleTcTyConBndrs [(TyCon, [(Name, TyVar)], Type)]
tc_infos)

       -- And finally generalise
       ; ((TyCon, [(Name, TyVar)], Type) -> TcRn TyCon)
-> [(TyCon, [(Name, TyVar)], Type)]
-> IOEnv (Env TcGblEnv TcLclEnv) [TyCon]
forall a b. (a -> TcRn b) -> [a] -> TcRn [b]
mapAndReportM (TyCon, [(Name, TyVar)], Type) -> TcRn TyCon
generaliseTcTyCon [(TyCon, [(Name, TyVar)], Type)]
swizzled_infos }
  where
    tycld_names :: TyClDecl GhcRn -> [Name]
    tycld_names :: TyClDecl GhcRn -> [Name]
tycld_names TyClDecl GhcRn
decl = TyClDecl GhcRn -> IdP GhcRn
forall (p :: Pass). TyClDecl (GhcPass p) -> IdP (GhcPass p)
tcdName TyClDecl GhcRn
decl Name -> [Name] -> [Name]
forall a. a -> [a] -> [a]
: TyClDecl GhcRn -> [Name]
at_names TyClDecl GhcRn
decl

    at_names :: TyClDecl GhcRn -> [Name]
    at_names :: TyClDecl GhcRn -> [Name]
at_names (ClassDecl { tcdATs :: forall pass. TyClDecl pass -> [LFamilyDecl pass]
tcdATs = [LFamilyDecl GhcRn]
ats }) = (LFamilyDecl GhcRn -> Name) -> [LFamilyDecl GhcRn] -> [Name]
forall a b. (a -> b) -> [a] -> [b]
map (FamilyDecl GhcRn -> Name
forall (p :: Pass). FamilyDecl (GhcPass p) -> IdP (GhcPass p)
familyDeclName (FamilyDecl GhcRn -> Name)
-> (LFamilyDecl GhcRn -> FamilyDecl GhcRn)
-> LFamilyDecl GhcRn
-> Name
forall b c a. (b -> c) -> (a -> b) -> a -> c
. LFamilyDecl GhcRn -> FamilyDecl GhcRn
forall l e. GenLocated l e -> e
unLoc) [LFamilyDecl GhcRn]
ats
    at_names TyClDecl GhcRn
_ = []  -- Only class decls have associated types

    skolemise_tc_tycon :: Name -> TcM (TcTyCon, ScopedPairs)
    -- Zonk and skolemise the Specified and Required binders
    skolemise_tc_tycon :: Name -> IOEnv (Env TcGblEnv TcLclEnv) (TyCon, [(Name, TyVar)])
skolemise_tc_tycon Name
tc_name
      = do { let tc :: TyCon
tc = NameEnv TyCon -> Name -> TyCon
forall a. NameEnv a -> Name -> a
lookupNameEnv_NF NameEnv TyCon
inferred_tc_env Name
tc_name
                      -- This lookup should not fail
           ; [(Name, TyVar)]
scoped_prs <- (TyVar -> IOEnv (Env TcGblEnv TcLclEnv) TyVar)
-> [(Name, TyVar)] -> IOEnv (Env TcGblEnv TcLclEnv) [(Name, TyVar)]
forall (m :: * -> *) b c a.
Monad m =>
(b -> m c) -> [(a, b)] -> m [(a, c)]
mapSndM TyVar -> IOEnv (Env TcGblEnv TcLclEnv) TyVar
zonkAndSkolemise (TyCon -> [(Name, TyVar)]
tcTyConScopedTyVars TyCon
tc)
           ; (TyCon, [(Name, TyVar)])
-> IOEnv (Env TcGblEnv TcLclEnv) (TyCon, [(Name, TyVar)])
forall (m :: * -> *) a. Monad m => a -> m a
return (TyCon
tc, [(Name, TyVar)]
scoped_prs) }

    zonk_tc_tycon :: (TcTyCon, ScopedPairs) -> TcM (TcTyCon, ScopedPairs, TcKind)
    zonk_tc_tycon :: (TyCon, [(Name, TyVar)])
-> IOEnv (Env TcGblEnv TcLclEnv) (TyCon, [(Name, TyVar)], Type)
zonk_tc_tycon (TyCon
tc, [(Name, TyVar)]
scoped_prs)
      = do { [(Name, TyVar)]
scoped_prs <- (TyVar -> IOEnv (Env TcGblEnv TcLclEnv) TyVar)
-> [(Name, TyVar)] -> IOEnv (Env TcGblEnv TcLclEnv) [(Name, TyVar)]
forall (m :: * -> *) b c a.
Monad m =>
(b -> m c) -> [(a, b)] -> m [(a, c)]
mapSndM HasDebugCallStack => TyVar -> IOEnv (Env TcGblEnv TcLclEnv) TyVar
TyVar -> IOEnv (Env TcGblEnv TcLclEnv) TyVar
zonkTcTyVarToTyVar [(Name, TyVar)]
scoped_prs
                           -- We really have to do this again, even though
                           -- we have just done zonkAndSkolemise
           ; Type
res_kind   <- Type -> TcM Type
zonkTcType (TyCon -> Type
tyConResKind TyCon
tc)
           ; (TyCon, [(Name, TyVar)], Type)
-> IOEnv (Env TcGblEnv TcLclEnv) (TyCon, [(Name, TyVar)], Type)
forall (m :: * -> *) a. Monad m => a -> m a
return (TyCon
tc, [(Name, TyVar)]
scoped_prs, Type
res_kind) }

swizzleTcTyConBndrs :: [(TcTyCon, ScopedPairs, TcKind)]
                -> TcM [(TcTyCon, ScopedPairs, TcKind)]
swizzleTcTyConBndrs :: [(TyCon, [(Name, TyVar)], Type)]
-> IOEnv (Env TcGblEnv TcLclEnv) [(TyCon, [(Name, TyVar)], Type)]
swizzleTcTyConBndrs [(TyCon, [(Name, TyVar)], Type)]
tc_infos
  | ((Name, TyVar) -> Bool) -> [(Name, TyVar)] -> Bool
forall (t :: * -> *) a. Foldable t => (a -> Bool) -> t a -> Bool
all (Name, TyVar) -> Bool
no_swizzle [(Name, TyVar)]
swizzle_prs
    -- This fast path happens almost all the time
    -- See Note [Non-cloning for tyvar binders] in GHC.Tc.Gen.HsType
  = do { String -> SDoc -> TcRn ()
traceTc String
"Skipping swizzleTcTyConBndrs for" ([TyCon] -> SDoc
forall a. Outputable a => a -> SDoc
ppr (((TyCon, [(Name, TyVar)], Type) -> TyCon)
-> [(TyCon, [(Name, TyVar)], Type)] -> [TyCon]
forall a b. (a -> b) -> [a] -> [b]
map (TyCon, [(Name, TyVar)], Type) -> TyCon
forall a b c. (a, b, c) -> a
fstOf3 [(TyCon, [(Name, TyVar)], Type)]
tc_infos))
       ; [(TyCon, [(Name, TyVar)], Type)]
-> IOEnv (Env TcGblEnv TcLclEnv) [(TyCon, [(Name, TyVar)], Type)]
forall (m :: * -> *) a. Monad m => a -> m a
return [(TyCon, [(Name, TyVar)], Type)]
tc_infos }

  | Bool
otherwise
  = do { TcRn ()
check_duplicate_tc_binders

       ; String -> SDoc -> TcRn ()
traceTc String
"swizzleTcTyConBndrs" (SDoc -> TcRn ()) -> SDoc -> TcRn ()
forall a b. (a -> b) -> a -> b
$
         [SDoc] -> SDoc
vcat [ String -> SDoc
text String
"before" SDoc -> SDoc -> SDoc
<+> [(TyCon, [(Name, TyVar)], Type)] -> SDoc
forall {a} {a} {c}. Outputable a => [(a, [(a, TyVar)], c)] -> SDoc
ppr_infos [(TyCon, [(Name, TyVar)], Type)]
tc_infos
              , String -> SDoc
text String
"swizzle_prs" SDoc -> SDoc -> SDoc
<+> [(Name, TyVar)] -> SDoc
forall a. Outputable a => a -> SDoc
ppr [(Name, TyVar)]
swizzle_prs
              , String -> SDoc
text String
"after" SDoc -> SDoc -> SDoc
<+> [(TyCon, [(Name, TyVar)], Type)] -> SDoc
forall {a} {a} {c}. Outputable a => [(a, [(a, TyVar)], c)] -> SDoc
ppr_infos [(TyCon, [(Name, TyVar)], Type)]
swizzled_infos ]

       ; [(TyCon, [(Name, TyVar)], Type)]
-> IOEnv (Env TcGblEnv TcLclEnv) [(TyCon, [(Name, TyVar)], Type)]
forall (m :: * -> *) a. Monad m => a -> m a
return [(TyCon, [(Name, TyVar)], Type)]
swizzled_infos }

  where
    swizzled_infos :: [(TyCon, [(Name, TyVar)], Type)]
swizzled_infos =  [ (TyCon
tc, (TyVar -> TyVar) -> [(Name, TyVar)] -> [(Name, TyVar)]
forall b c a. (b -> c) -> [(a, b)] -> [(a, c)]
mapSnd TyVar -> TyVar
swizzle_var [(Name, TyVar)]
scoped_prs, Type -> Type
swizzle_ty Type
kind)
                      | (TyCon
tc, [(Name, TyVar)]
scoped_prs, Type
kind) <- [(TyCon, [(Name, TyVar)], Type)]
tc_infos ]

    swizzle_prs :: [(Name,TyVar)]
    -- Pairs the user-specifed Name with its representative TyVar
    -- See Note [Swizzling the tyvars before generaliseTcTyCon]
    swizzle_prs :: [(Name, TyVar)]
swizzle_prs = [ (Name, TyVar)
pr | (TyCon
_, [(Name, TyVar)]
prs, Type
_) <- [(TyCon, [(Name, TyVar)], Type)]
tc_infos, (Name, TyVar)
pr <- [(Name, TyVar)]
prs ]

    no_swizzle :: (Name,TyVar) -> Bool
    no_swizzle :: (Name, TyVar) -> Bool
no_swizzle (Name
nm, TyVar
tv) = Name
nm Name -> Name -> Bool
forall a. Eq a => a -> a -> Bool
== TyVar -> Name
tyVarName TyVar
tv

    ppr_infos :: [(a, [(a, TyVar)], c)] -> SDoc
ppr_infos [(a, [(a, TyVar)], c)]
infos = [SDoc] -> SDoc
vcat [ a -> SDoc
forall a. Outputable a => a -> SDoc
ppr a
tc SDoc -> SDoc -> SDoc
<+> [TyVar] -> SDoc
pprTyVars (((a, TyVar) -> TyVar) -> [(a, TyVar)] -> [TyVar]
forall a b. (a -> b) -> [a] -> [b]
map (a, TyVar) -> TyVar
forall a b. (a, b) -> b
snd [(a, TyVar)]
prs)
                           | (a
tc, [(a, TyVar)]
prs, c
_) <- [(a, [(a, TyVar)], c)]
infos ]

    -- Check for duplicates
    -- E.g. data SameKind (a::k) (b::k)
    --      data T (a::k1) (b::k2) = MkT (SameKind a b)
    -- Here k1 and k2 start as TyVarTvs, and get unified with each other
    -- If this happens, things get very confused later, so fail fast
    check_duplicate_tc_binders :: TcM ()
    check_duplicate_tc_binders :: TcRn ()
check_duplicate_tc_binders = Bool -> TcRn () -> TcRn ()
forall (f :: * -> *). Applicative f => Bool -> f () -> f ()
unless ([(Name, Name)] -> Bool
forall (t :: * -> *) a. Foldable t => t a -> Bool
null [(Name, Name)]
err_prs) (TcRn () -> TcRn ()) -> TcRn () -> TcRn ()
forall a b. (a -> b) -> a -> b
$
                                 do { ((Name, Name) -> TcRn ()) -> [(Name, Name)] -> TcRn ()
forall (t :: * -> *) (m :: * -> *) a b.
(Foldable t, Monad m) =>
(a -> m b) -> t a -> m ()
mapM_ (Name, Name) -> TcRn ()
report_dup [(Name, Name)]
err_prs; TcRn ()
forall env a. IOEnv env a
failM }

    -------------- Error reporting ------------
    err_prs :: [(Name,Name)]
    err_prs :: [(Name, Name)]
err_prs = [ (Name
n1,Name
n2)
              | (Name, TyVar)
pr :| [(Name, TyVar)]
prs <- ((Name, TyVar) -> (Name, TyVar) -> Bool)
-> [(Name, TyVar)] -> [NonEmpty (Name, TyVar)]
forall a. (a -> a -> Bool) -> [a] -> [NonEmpty a]
findDupsEq (TyVar -> TyVar -> Bool
forall a. Eq a => a -> a -> Bool
(==) (TyVar -> TyVar -> Bool)
-> ((Name, TyVar) -> TyVar)
-> (Name, TyVar)
-> (Name, TyVar)
-> Bool
forall b c a. (b -> b -> c) -> (a -> b) -> a -> a -> c
`on` (Name, TyVar) -> TyVar
forall a b. (a, b) -> b
snd) [(Name, TyVar)]
swizzle_prs
              , (Name
n1,TyVar
_):(Name
n2,TyVar
_):[(Name, TyVar)]
_ <- [((Name, TyVar) -> (Name, TyVar) -> Bool)
-> [(Name, TyVar)] -> [(Name, TyVar)]
forall a. (a -> a -> Bool) -> [a] -> [a]
nubBy (Name -> Name -> Bool
forall a. Eq a => a -> a -> Bool
(==) (Name -> Name -> Bool)
-> ((Name, TyVar) -> Name)
-> (Name, TyVar)
-> (Name, TyVar)
-> Bool
forall b c a. (b -> b -> c) -> (a -> b) -> a -> a -> c
`on` (Name, TyVar) -> Name
forall a b. (a, b) -> a
fst) ((Name, TyVar)
pr(Name, TyVar) -> [(Name, TyVar)] -> [(Name, TyVar)]
forall a. a -> [a] -> [a]
:[(Name, TyVar)]
prs)] ]
              -- This nubBy avoids bogus error reports when we have
              --    [("f", f), ..., ("f",f)....] in swizzle_prs
              -- which happens with  class C f where { type T f }

    report_dup :: (Name,Name) -> TcM ()
    report_dup :: (Name, Name) -> TcRn ()
report_dup (Name
n1,Name
n2)
      = SrcSpan -> TcRn () -> TcRn ()
forall a. SrcSpan -> TcRn a -> TcRn a
setSrcSpan (Name -> SrcSpan
forall a. NamedThing a => a -> SrcSpan
getSrcSpan Name
n2) (TcRn () -> TcRn ()) -> TcRn () -> TcRn ()
forall a b. (a -> b) -> a -> b
$ SDoc -> TcRn ()
addErrTc (SDoc -> TcRn ()) -> SDoc -> TcRn ()
forall a b. (a -> b) -> a -> b
$
        SDoc -> Arity -> SDoc -> SDoc
hang (String -> SDoc
text String
"Different names for the same type variable:") Arity
2 SDoc
info
      where
        info :: SDoc
info | Name -> OccName
nameOccName Name
n1 OccName -> OccName -> Bool
forall a. Eq a => a -> a -> Bool
/= Name -> OccName
nameOccName Name
n2
             = SDoc -> SDoc
quotes (Name -> SDoc
forall a. Outputable a => a -> SDoc
ppr Name
n1) SDoc -> SDoc -> SDoc
<+> String -> SDoc
text String
"and" SDoc -> SDoc -> SDoc
<+> SDoc -> SDoc
quotes (Name -> SDoc
forall a. Outputable a => a -> SDoc
ppr Name
n2)
             | Bool
otherwise -- Same OccNames! See C2 in
                         -- Note [Swizzling the tyvars before generaliseTcTyCon]
             = [SDoc] -> SDoc
vcat [ SDoc -> SDoc
quotes (Name -> SDoc
forall a. Outputable a => a -> SDoc
ppr Name
n1) SDoc -> SDoc -> SDoc
<+> String -> SDoc
text String
"bound at" SDoc -> SDoc -> SDoc
<+> SrcLoc -> SDoc
forall a. Outputable a => a -> SDoc
ppr (Name -> SrcLoc
forall a. NamedThing a => a -> SrcLoc
getSrcLoc Name
n1)
                    , SDoc -> SDoc
quotes (Name -> SDoc
forall a. Outputable a => a -> SDoc
ppr Name
n2) SDoc -> SDoc -> SDoc
<+> String -> SDoc
text String
"bound at" SDoc -> SDoc -> SDoc
<+> SrcLoc -> SDoc
forall a. Outputable a => a -> SDoc
ppr (Name -> SrcLoc
forall a. NamedThing a => a -> SrcLoc
getSrcLoc Name
n2) ]

    -------------- The swizzler ------------
    -- This does a deep traverse, simply doing a
    -- Name-to-Name change, governed by swizzle_env
    -- The 'swap' is what gets from the representative TyVar
    -- back to the original user-specified Name
    swizzle_env :: VarEnv Name
swizzle_env = [(TyVar, Name)] -> VarEnv Name
forall a. [(TyVar, a)] -> VarEnv a
mkVarEnv (((Name, TyVar) -> (TyVar, Name))
-> [(Name, TyVar)] -> [(TyVar, Name)]
forall a b. (a -> b) -> [a] -> [b]
map (Name, TyVar) -> (TyVar, Name)
forall a b. (a, b) -> (b, a)
swap [(Name, TyVar)]
swizzle_prs)

    swizzleMapper :: TyCoMapper () Identity
    swizzleMapper :: TyCoMapper () Identity
swizzleMapper = TyCoMapper :: forall env (m :: * -> *).
(env -> TyVar -> m Type)
-> (env -> TyVar -> m Coercion)
-> (env -> CoercionHole -> m Coercion)
-> (env -> TyVar -> ArgFlag -> m (env, TyVar))
-> (TyCon -> m TyCon)
-> TyCoMapper env m
TyCoMapper { tcm_tyvar :: () -> TyVar -> Identity Type
tcm_tyvar = () -> TyVar -> Identity Type
forall {m :: * -> *} {p}. Monad m => p -> TyVar -> m Type
swizzle_tv
                               , tcm_covar :: () -> TyVar -> Identity Coercion
tcm_covar = () -> TyVar -> Identity Coercion
forall {m :: * -> *} {p}. Monad m => p -> TyVar -> m Coercion
swizzle_cv
                               , tcm_hole :: () -> CoercionHole -> Identity Coercion
tcm_hole  = () -> CoercionHole -> Identity Coercion
forall {a} {p} {a}. Outputable a => p -> a -> a
swizzle_hole
                               , tcm_tycobinder :: () -> TyVar -> ArgFlag -> Identity ((), TyVar)
tcm_tycobinder = () -> TyVar -> ArgFlag -> Identity ((), TyVar)
forall {m :: * -> *} {p} {p}.
Monad m =>
p -> TyVar -> p -> m ((), TyVar)
swizzle_bndr
                               , tcm_tycon :: TyCon -> Identity TyCon
tcm_tycon      = TyCon -> Identity TyCon
forall {a} {a}. Outputable a => a -> a
swizzle_tycon }
    swizzle_hole :: p -> a -> a
swizzle_hole  p
_ a
hole = String -> SDoc -> a
forall a. HasCallStack => String -> SDoc -> a
pprPanic String
"swizzle_hole" (a -> SDoc
forall a. Outputable a => a -> SDoc
ppr a
hole)
       -- These types are pre-zonked
    swizzle_tycon :: a -> a
swizzle_tycon a
tc = String -> SDoc -> a
forall a. HasCallStack => String -> SDoc -> a
pprPanic String
"swizzle_tc" (a -> SDoc
forall a. Outputable a => a -> SDoc
ppr a
tc)
       -- TcTyCons can't appear in kinds (yet)
    swizzle_tv :: p -> TyVar -> m Type
swizzle_tv p
_ TyVar
tv = Type -> m Type
forall (m :: * -> *) a. Monad m => a -> m a
return (TyVar -> Type
mkTyVarTy (TyVar -> TyVar
swizzle_var TyVar
tv))
    swizzle_cv :: p -> TyVar -> m Coercion
swizzle_cv p
_ TyVar
cv = Coercion -> m Coercion
forall (m :: * -> *) a. Monad m => a -> m a
return (TyVar -> Coercion
mkCoVarCo (TyVar -> TyVar
swizzle_var TyVar
cv))

    swizzle_bndr :: p -> TyVar -> p -> m ((), TyVar)
swizzle_bndr p
_ TyVar
tcv p
_
      = ((), TyVar) -> m ((), TyVar)
forall (m :: * -> *) a. Monad m => a -> m a
return ((), TyVar -> TyVar
swizzle_var TyVar
tcv)

    swizzle_var :: Var -> Var
    swizzle_var :: TyVar -> TyVar
swizzle_var TyVar
v
      | Just Name
nm <- VarEnv Name -> TyVar -> Maybe Name
forall a. VarEnv a -> TyVar -> Maybe a
lookupVarEnv VarEnv Name
swizzle_env TyVar
v
      = (Type -> Type) -> TyVar -> TyVar
updateVarType Type -> Type
swizzle_ty (TyVar
v TyVar -> Name -> TyVar
`setVarName` Name
nm)
      | Bool
otherwise
      = (Type -> Type) -> TyVar -> TyVar
updateVarType Type -> Type
swizzle_ty TyVar
v

    (Type -> Identity Type
map_type, [Type] -> Identity [Type]
_, Coercion -> Identity Coercion
_, [Coercion] -> Identity [Coercion]
_) = TyCoMapper () Identity
-> (Type -> Identity Type, [Type] -> Identity [Type],
    Coercion -> Identity Coercion, [Coercion] -> Identity [Coercion])
forall (m :: * -> *).
Monad m =>
TyCoMapper () m
-> (Type -> m Type, [Type] -> m [Type], Coercion -> m Coercion,
    [Coercion] -> m [Coercion])
mapTyCo TyCoMapper () Identity
swizzleMapper
    swizzle_ty :: Type -> Type
swizzle_ty Type
ty = Identity Type -> Type
forall a. Identity a -> a
runIdentity (Type -> Identity Type
map_type Type
ty)


generaliseTcTyCon :: (TcTyCon, ScopedPairs, TcKind) -> TcM TcTyCon
generaliseTcTyCon :: (TyCon, [(Name, TyVar)], Type) -> TcRn TyCon
generaliseTcTyCon (TyCon
tc, [(Name, TyVar)]
scoped_prs, Type
tc_res_kind)
  -- See Note [Required, Specified, and Inferred for types]
  = SrcSpan -> TcRn TyCon -> TcRn TyCon
forall a. SrcSpan -> TcRn a -> TcRn a
setSrcSpan (TyCon -> SrcSpan
forall a. NamedThing a => a -> SrcSpan
getSrcSpan TyCon
tc) (TcRn TyCon -> TcRn TyCon) -> TcRn TyCon -> TcRn TyCon
forall a b. (a -> b) -> a -> b
$
    TyCon -> TcRn TyCon -> TcRn TyCon
forall a. TyCon -> TcM a -> TcM a
addTyConCtxt TyCon
tc (TcRn TyCon -> TcRn TyCon) -> TcRn TyCon -> TcRn TyCon
forall a b. (a -> b) -> a -> b
$
    do { -- Step 1: Separate Specified from Required variables
         -- NB: spec_req_tvs = spec_tvs ++ req_tvs
         --     And req_tvs is 1-1 with tyConTyVars
         --     See Note [Scoped tyvars in a TcTyCon] in GHC.Core.TyCon
       ; let spec_req_tvs :: [TyVar]
spec_req_tvs        = ((Name, TyVar) -> TyVar) -> [(Name, TyVar)] -> [TyVar]
forall a b. (a -> b) -> [a] -> [b]
map (Name, TyVar) -> TyVar
forall a b. (a, b) -> b
snd [(Name, TyVar)]
scoped_prs
             n_spec :: Arity
n_spec              = [TyVar] -> Arity
forall (t :: * -> *) a. Foldable t => t a -> Arity
length [TyVar]
spec_req_tvs Arity -> Arity -> Arity
forall a. Num a => a -> a -> a
- TyCon -> Arity
tyConArity TyCon
tc
             ([TyVar]
spec_tvs, [TyVar]
req_tvs) = Arity -> [TyVar] -> ([TyVar], [TyVar])
forall a. Arity -> [a] -> ([a], [a])
splitAt Arity
n_spec [TyVar]
spec_req_tvs
             sorted_spec_tvs :: [TyVar]
sorted_spec_tvs     = [TyVar] -> [TyVar]
scopedSort [TyVar]
spec_tvs
                 -- NB: We can't do the sort until we've zonked
                 --     Maintain the L-R order of scoped_tvs

       -- Step 2a: find all the Inferred variables we want to quantify over
       ; CandidatesQTvs
dvs1 <- [Type] -> TcM CandidatesQTvs
candidateQTyVarsOfKinds ([Type] -> TcM CandidatesQTvs) -> [Type] -> TcM CandidatesQTvs
forall a b. (a -> b) -> a -> b
$
                 (Type
tc_res_kind Type -> [Type] -> [Type]
forall a. a -> [a] -> [a]
: (TyVar -> Type) -> [TyVar] -> [Type]
forall a b. (a -> b) -> [a] -> [b]
map TyVar -> Type
tyVarKind [TyVar]
spec_req_tvs)
       ; let dvs2 :: CandidatesQTvs
dvs2 = CandidatesQTvs
dvs1 CandidatesQTvs -> [TyVar] -> CandidatesQTvs
`delCandidates` [TyVar]
spec_req_tvs

       -- Step 2b: quantify, mainly meaning skolemise the free variables
       -- Returned 'inferred' are scope-sorted and skolemised
       ; [TyVar]
inferred <- CandidatesQTvs -> TcM [TyVar]
quantifyTyVars CandidatesQTvs
dvs2

       ; String -> SDoc -> TcRn ()
traceTc String
"generaliseTcTyCon: pre zonk"
           ([SDoc] -> SDoc
vcat [ String -> SDoc
text String
"tycon =" SDoc -> SDoc -> SDoc
<+> TyCon -> SDoc
forall a. Outputable a => a -> SDoc
ppr TyCon
tc
                 , String -> SDoc
text String
"spec_req_tvs =" SDoc -> SDoc -> SDoc
<+> [TyVar] -> SDoc
pprTyVars [TyVar]
spec_req_tvs
                 , String -> SDoc
text String
"tc_res_kind =" SDoc -> SDoc -> SDoc
<+> Type -> SDoc
forall a. Outputable a => a -> SDoc
ppr Type
tc_res_kind
                 , String -> SDoc
text String
"dvs1 =" SDoc -> SDoc -> SDoc
<+> CandidatesQTvs -> SDoc
forall a. Outputable a => a -> SDoc
ppr CandidatesQTvs
dvs1
                 , String -> SDoc
text String
"inferred =" SDoc -> SDoc -> SDoc
<+> [TyVar] -> SDoc
pprTyVars [TyVar]
inferred ])

       -- Step 3: Final zonk (following kind generalisation)
       -- See Note [Swizzling the tyvars before generaliseTcTyCon]
       ; ZonkEnv
ze <- TcM ZonkEnv
emptyZonkEnv
       ; (ZonkEnv
ze, [TyVar]
inferred)        <- ZonkEnv -> [TyVar] -> TcM (ZonkEnv, [TyVar])
zonkTyBndrsX ZonkEnv
ze [TyVar]
inferred
       ; (ZonkEnv
ze, [TyVar]
sorted_spec_tvs) <- ZonkEnv -> [TyVar] -> TcM (ZonkEnv, [TyVar])
zonkTyBndrsX ZonkEnv
ze [TyVar]
sorted_spec_tvs
       ; (ZonkEnv
ze, [TyVar]
req_tvs)         <- ZonkEnv -> [TyVar] -> TcM (ZonkEnv, [TyVar])
zonkTyBndrsX ZonkEnv
ze [TyVar]
req_tvs
       ; Type
tc_res_kind           <- ZonkEnv -> Type -> TcM Type
zonkTcTypeToTypeX ZonkEnv
ze Type
tc_res_kind

       ; String -> SDoc -> TcRn ()
traceTc String
"generaliseTcTyCon: post zonk" (SDoc -> TcRn ()) -> SDoc -> TcRn ()
forall a b. (a -> b) -> a -> b
$
         [SDoc] -> SDoc
vcat [ String -> SDoc
text String
"tycon =" SDoc -> SDoc -> SDoc
<+> TyCon -> SDoc
forall a. Outputable a => a -> SDoc
ppr TyCon
tc
              , String -> SDoc
text String
"inferred =" SDoc -> SDoc -> SDoc
<+> [TyVar] -> SDoc
pprTyVars [TyVar]
inferred
              , String -> SDoc
text String
"spec_req_tvs =" SDoc -> SDoc -> SDoc
<+> [TyVar] -> SDoc
pprTyVars [TyVar]
spec_req_tvs
              , String -> SDoc
text String
"sorted_spec_tvs =" SDoc -> SDoc -> SDoc
<+> [TyVar] -> SDoc
pprTyVars [TyVar]
sorted_spec_tvs
              , String -> SDoc
text String
"req_tvs =" SDoc -> SDoc -> SDoc
<+> [TyVar] -> SDoc
forall a. Outputable a => a -> SDoc
ppr [TyVar]
req_tvs
              , String -> SDoc
text String
"zonk-env =" SDoc -> SDoc -> SDoc
<+> ZonkEnv -> SDoc
forall a. Outputable a => a -> SDoc
ppr ZonkEnv
ze ]

       -- Step 4: Make the TyConBinders.
       ; let dep_fv_set :: VarSet
dep_fv_set     = CandidatesQTvs -> VarSet
candidateKindVars CandidatesQTvs
dvs1
             inferred_tcbs :: [TyConBinder]
inferred_tcbs  = ArgFlag -> [TyVar] -> [TyConBinder]
mkNamedTyConBinders ArgFlag
Inferred [TyVar]
inferred
             specified_tcbs :: [TyConBinder]
specified_tcbs = ArgFlag -> [TyVar] -> [TyConBinder]
mkNamedTyConBinders ArgFlag
Specified [TyVar]
sorted_spec_tvs
             required_tcbs :: [TyConBinder]
required_tcbs  = (TyVar -> TyConBinder) -> [TyVar] -> [TyConBinder]
forall a b. (a -> b) -> [a] -> [b]
map (VarSet -> TyVar -> TyConBinder
mkRequiredTyConBinder VarSet
dep_fv_set) [TyVar]
req_tvs

       -- Step 5: Assemble the final list.
             final_tcbs :: [TyConBinder]
final_tcbs = [[TyConBinder]] -> [TyConBinder]
forall (t :: * -> *) a. Foldable t => t [a] -> [a]
concat [ [TyConBinder]
inferred_tcbs
                                 , [TyConBinder]
specified_tcbs
                                 , [TyConBinder]
required_tcbs ]

       -- Step 6: Make the result TcTyCon
             tycon :: TyCon
tycon = Name
-> [TyConBinder]
-> Type
-> [(Name, TyVar)]
-> Bool
-> TyConFlavour
-> TyCon
mkTcTyCon (TyCon -> Name
tyConName TyCon
tc) [TyConBinder]
final_tcbs Type
tc_res_kind
                            ([TyVar] -> [(Name, TyVar)]
mkTyVarNamePairs ([TyVar]
sorted_spec_tvs [TyVar] -> [TyVar] -> [TyVar]
forall a. [a] -> [a] -> [a]
++ [TyVar]
req_tvs))
                            Bool
True {- it's generalised now -}
                            (TyCon -> TyConFlavour
tyConFlavour TyCon
tc)

       ; String -> SDoc -> TcRn ()
traceTc String
"generaliseTcTyCon done" (SDoc -> TcRn ()) -> SDoc -> TcRn ()
forall a b. (a -> b) -> a -> b
$
         [SDoc] -> SDoc
vcat [ String -> SDoc
text String
"tycon =" SDoc -> SDoc -> SDoc
<+> TyCon -> SDoc
forall a. Outputable a => a -> SDoc
ppr TyCon
tc
              , String -> SDoc
text String
"tc_res_kind =" SDoc -> SDoc -> SDoc
<+> Type -> SDoc
forall a. Outputable a => a -> SDoc
ppr Type
tc_res_kind
              , String -> SDoc
text String
"dep_fv_set =" SDoc -> SDoc -> SDoc
<+> VarSet -> SDoc
forall a. Outputable a => a -> SDoc
ppr VarSet
dep_fv_set
              , String -> SDoc
text String
"inferred_tcbs =" SDoc -> SDoc -> SDoc
<+> [TyConBinder] -> SDoc
forall a. Outputable a => a -> SDoc
ppr [TyConBinder]
inferred_tcbs
              , String -> SDoc
text String
"specified_tcbs =" SDoc -> SDoc -> SDoc
<+> [TyConBinder] -> SDoc
forall a. Outputable a => a -> SDoc
ppr [TyConBinder]
specified_tcbs
              , String -> SDoc
text String
"required_tcbs =" SDoc -> SDoc -> SDoc
<+> [TyConBinder] -> SDoc
forall a. Outputable a => a -> SDoc
ppr [TyConBinder]
required_tcbs
              , String -> SDoc
text String
"final_tcbs =" SDoc -> SDoc -> SDoc
<+> [TyConBinder] -> SDoc
forall a. Outputable a => a -> SDoc
ppr [TyConBinder]
final_tcbs ]

       -- Step 7: Check for validity.
       -- We do this here because we're about to put the tycon into the
       -- the environment, and we don't want anything malformed there
       ; TyCon -> TcRn ()
checkTyConTelescope TyCon
tycon

       ; TyCon -> TcRn TyCon
forall (m :: * -> *) a. Monad m => a -> m a
return TyCon
tycon }

{- Note [Required, Specified, and Inferred for types]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Each forall'd type variable in a type or kind is one of

  * Required: an argument must be provided at every call site

  * Specified: the argument can be inferred at call sites, but
    may be instantiated with visible type/kind application

  * Inferred: the must be inferred at call sites; it
    is unavailable for use with visible type/kind application.

Why have Inferred at all? Because we just can't make user-facing
promises about the ordering of some variables. These might swizzle
around even between minor released. By forbidding visible type
application, we ensure users aren't caught unawares.

Go read Note [VarBndrs, TyCoVarBinders, TyConBinders, and visibility] in GHC.Core.TyCo.Rep.

The question for this Note is this:
   given a TyClDecl, how are its quantified type variables classified?
Much of the debate is memorialized in #15743.

Here is our design choice. When inferring the ordering of variables
for a TyCl declaration (that is, for those variables that he user
has not specified the order with an explicit `forall`), we use the
following order:

 1. Inferred variables
 2. Specified variables; in the left-to-right order in which
    the user wrote them, modified by scopedSort (see below)
    to put them in depdendency order.
 3. Required variables before a top-level ::
 4. All variables after a top-level ::

If this ordering does not make a valid telescope, we reject the definition.

Example:
  data SameKind :: k -> k -> *
  data Bad a (c :: Proxy b) (d :: Proxy a) (x :: SameKind b d)

For Bad:
  - a, c, d, x are Required; they are explicitly listed by the user
    as the positional arguments of Bad
  - b is Specified; it appears explicitly in a kind signature
  - k, the kind of a, is Inferred; it is not mentioned explicitly at all

Putting variables in the order Inferred, Specified, Required
gives us this telescope:
  Inferred:  k
  Specified: b : Proxy a
  Required : (a : k) (c : Proxy b) (d : Proxy a) (x : SameKind b d)

But this order is ill-scoped, because b's kind mentions a, which occurs
after b in the telescope. So we reject Bad.

Associated types
~~~~~~~~~~~~~~~~
For associated types everything above is determined by the
associated-type declaration alone, ignoring the class header.
Here is an example (#15592)
  class C (a :: k) b where
    type F (x :: b a)

In the kind of C, 'k' is Specified.  But what about F?
In the kind of F,

 * Should k be Inferred or Specified?  It's Specified for C,
   but not mentioned in F's declaration.

 * In which order should the Specified variables a and b occur?
   It's clearly 'a' then 'b' in C's declaration, but the L-R ordering
   in F's declaration is 'b' then 'a'.

In both cases we make the choice by looking at F's declaration alone,
so it gets the kind
   F :: forall {k}. forall b a. b a -> Type

How it works
~~~~~~~~~~~~
These design choices are implemented by two completely different code
paths for

  * Declarations with a standalone kind signature or a complete user-specified
    kind signature (CUSK). Handled by the kcCheckDeclHeader.

  * Declarations without a kind signature (standalone or CUSK) are handled by
    kcInferDeclHeader; see Note [Inferring kinds for type declarations].

Note that neither code path worries about point (4) above, as this
is nicely handled by not mangling the res_kind. (Mangling res_kinds is done
*after* all this stuff, in tcDataDefn's call to etaExpandAlgTyCon.)

We can tell Inferred apart from Specified by looking at the scoped
tyvars; Specified are always included there.

Design alternatives
~~~~~~~~~~~~~~~~~~~
* For associated types we considered putting the class variables
  before the local variables, in a nod to the treatment for class
  methods. But it got too compilicated; see #15592, comment:21ff.

* We rigidly require the ordering above, even though we could be much more
  permissive. Relevant musings are at
  https://gitlab.haskell.org/ghc/ghc/issues/15743#note_161623
  The bottom line conclusion is that, if the user wants a different ordering,
  then can specify it themselves, and it is better to be predictable and dumb
  than clever and capricious.

  I (Richard) conjecture we could be fully permissive, allowing all classes
  of variables to intermix. We would have to augment ScopedSort to refuse to
  reorder Required variables (or check that it wouldn't have). But this would
  allow more programs. See #15743 for examples. Interestingly, Idris seems
  to allow this intermixing. The intermixing would be fully specified, in that
  we can be sure that inference wouldn't change between versions. However,
  would users be able to predict it? That I cannot answer.

Test cases (and tickets) relevant to these design decisions
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
  T15591*
  T15592*
  T15743*

Note [Inferring kinds for type declarations]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
This note deals with /inference/ for type declarations
that do not have a CUSK.  Consider
  data T (a :: k1) k2 (x :: k2) = MkT (S a k2 x)
  data S (b :: k3) k4 (y :: k4) = MkS (T b k4 y)

We do kind inference as follows:

* Step 1: inferInitialKinds, and in particular kcInferDeclHeader.
  Make a unification variable for each of the Required and Specified
  type variables in the header.

  Record the connection between the Names the user wrote and the
  fresh unification variables in the tcTyConScopedTyVars field
  of the TcTyCon we are making
      [ (a,  aa)
      , (k1, kk1)
      , (k2, kk2)
      , (x,  xx) ]
  (I'm using the convention that double letter like 'aa' or 'kk'
  mean a unification variable.)

  These unification variables
    - Are TyVarTvs: that is, unification variables that can
      unify only with other type variables.
      See Note [Signature skolems] in GHC.Tc.Utils.TcType

    - Have complete fresh Names; see GHC.Tc.Utils.TcMType
      Note [Unification variables need fresh Names]

  Assign initial monomorphic kinds to S, T
          T :: kk1 -> * -> kk2 -> *
          S :: kk3 -> * -> kk4 -> *

* Step 2: kcTyClDecl. Extend the environment with a TcTyCon for S and
  T, with these monomorphic kinds.  Now kind-check the declarations,
  and solve the resulting equalities.  The goal here is to discover
  constraints on all these unification variables.

  Here we find that kk1 := kk3, and kk2 := kk4.

  This is why we can't use skolems for kk1 etc; they have to
  unify with each other.

* Step 3: generaliseTcTyCon. Generalise each TyCon in turn.
  We find the free variables of the kind, skolemise them,
  sort them out into Inferred/Required/Specified (see the above
  Note [Required, Specified, and Inferred for types]),
  and perform some validity checks.

  This makes the utterly-final TyConBinders for the TyCon.

  All this is very similar at the level of terms: see GHC.Tc.Gen.Bind
  Note [Quantified variables in partial type signatures]

  But there some tricky corners: Note [Tricky scoping in generaliseTcTyCon]

* Step 4.  Extend the type environment with a TcTyCon for S and T, now
  with their utterly-final polymorphic kinds (needed for recursive
  occurrences of S, T).  Now typecheck the declarations, and build the
  final AlgTyCon for S and T resp.

The first three steps are in kcTyClGroup; the fourth is in
tcTyClDecls.

There are some wrinkles

* Do not default TyVarTvs.  We always want to kind-generalise over
  TyVarTvs, and /not/ default them to Type. By definition a TyVarTv is
  not allowed to unify with a type; it must stand for a type
  variable. Hence the check in GHC.Tc.Solver.defaultTyVarTcS, and
  GHC.Tc.Utils.TcMType.defaultTyVar.  Here's another example (#14555):
     data Exp :: [TYPE rep] -> TYPE rep -> Type where
        Lam :: Exp (a:xs) b -> Exp xs (a -> b)
  We want to kind-generalise over the 'rep' variable.
  #14563 is another example.

* Duplicate type variables. Consider #11203
    data SameKind :: k -> k -> *
    data Q (a :: k1) (b :: k2) c = MkQ (SameKind a b)
  Here we will unify k1 with k2, but this time doing so is an error,
  because k1 and k2 are bound in the same declaration.

  We spot this during validity checking (findDupTyVarTvs),
  in generaliseTcTyCon.

* Required arguments.  Even the Required arguments should be made
  into TyVarTvs, not skolems.  Consider
    data T k (a :: k)
  Here, k is a Required, dependent variable. For uniformity, it is helpful
  to have k be a TyVarTv, in parallel with other dependent variables.

* Duplicate skolemisation is expected.  When generalising in Step 3,
  we may find that one of the variables we want to quantify has
  already been skolemised.  For example, suppose we have already
  generalise S. When we come to T we'll find that kk1 (now the same as
  kk3) has already been skolemised.

  That's fine -- but it means that
    a) when collecting quantification candidates, in
       candidateQTyVarsOfKind, we must collect skolems
    b) quantifyTyVars should be a no-op on such a skolem

Note [Tricky scoping in generaliseTcTyCon]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Consider #16342
  class C (a::ka) x where
    cop :: D a x => x -> Proxy a -> Proxy a
    cop _ x = x :: Proxy (a::ka)

  class D (b::kb) y where
    dop :: C b y => y -> Proxy b -> Proxy b
    dop _ x = x :: Proxy (b::kb)

C and D are mutually recursive, by the time we get to
generaliseTcTyCon we'll have unified kka := kkb.

But when typechecking the default declarations for 'cop' and 'dop' in
tcDlassDecl2 we need {a, ka} and {b, kb} respectively to be in scope.
But at that point all we have is the utterly-final Class itself.

Conclusion: the classTyVars of a class must have the same Name as
that originally assigned by the user.  In our example, C must have
classTyVars {a, ka, x} while D has classTyVars {a, kb, y}.  Despite
the fact that kka and kkb got unified!

We achieve this sleight of hand in generaliseTcTyCon, using
the specialised function zonkRecTyVarBndrs.  We make the call
   zonkRecTyVarBndrs [ka,a,x] [kkb,aa,xxx]
where the [ka,a,x] are the Names originally assigned by the user, and
[kkb,aa,xx] are the corresponding (post-zonking, skolemised) TcTyVars.
zonkRecTyVarBndrs builds a recursive ZonkEnv that binds
   kkb :-> (ka :: <zonked kind of kkb>)
   aa  :-> (a  :: <konked kind of aa>)
   etc
That is, it maps each skolemised TcTyVars to the utterly-final
TyVar to put in the class, with its correct user-specified name.
When generalising D we'll do the same thing, but the ZonkEnv will map
   kkb :-> (kb :: <zonked kind of kkb>)
   bb  :-> (b  :: <konked kind of bb>)
   etc
Note that 'kkb' again appears in the domain of the mapping, but this
time mapped to 'kb'.  That's how C and D end up with differently-named
final TyVars despite the fact that we unified kka:=kkb

zonkRecTyVarBndrs we need to do knot-tying because of the need to
apply this same substitution to the kind of each.

Note [Inferring visible dependent quantification]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Consider

  data T k :: k -> Type where
    MkT1 :: T Type Int
    MkT2 :: T (Type -> Type) Maybe

This looks like it should work. However, it is polymorphically recursive,
as the uses of T in the constructor types specialize the k in the kind
of T. This trips up our dear users (#17131, #17541), and so we add
a "landmark" context (which cannot be suppressed) whenever we
spot inferred visible dependent quantification (VDQ).

It's hard to know when we've actually been tripped up by polymorphic recursion
specifically, so we just include a note to users whenever we infer VDQ. The
testsuite did not show up a single spurious inclusion of this message.

The context is added in addVDQNote, which looks for a visible TyConBinder
that also appears in the TyCon's kind. (I first looked at the kind for
a visible, dependent quantifier, but Note [No polymorphic recursion] in
GHC.Tc.Gen.HsType defeats that approach.) addVDQNote is used in kcTyClDecl,
which is used only when inferring the kind of a tycon (never with a CUSK or
SAK).

Once upon a time, I (Richard E) thought that the tycon-kind could
not be a forall-type. But this is wrong: data T :: forall k. k -> Type
(with -XNoCUSKs) could end up here. And this is all OK.


-}

--------------
tcExtendKindEnvWithTyCons :: [TcTyCon] -> TcM a -> TcM a
tcExtendKindEnvWithTyCons :: forall a. [TyCon] -> TcM a -> TcM a
tcExtendKindEnvWithTyCons [TyCon]
tcs
  = [(Name, TcTyThing)] -> TcM a -> TcM a
forall r. [(Name, TcTyThing)] -> TcM r -> TcM r
tcExtendKindEnvList [ (TyCon -> Name
tyConName TyCon
tc, TyCon -> TcTyThing
ATcTyCon TyCon
tc) | TyCon
tc <- [TyCon]
tcs ]

--------------
mkPromotionErrorEnv :: [LTyClDecl GhcRn] -> TcTypeEnv
-- Maps each tycon/datacon to a suitable promotion error
--    tc :-> APromotionErr TyConPE
--    dc :-> APromotionErr RecDataConPE
--    See Note [Recursion and promoting data constructors]

mkPromotionErrorEnv :: [LTyClDecl GhcRn] -> TcTypeEnv
mkPromotionErrorEnv [LTyClDecl GhcRn]
decls
  = (LTyClDecl GhcRn -> TcTypeEnv -> TcTypeEnv)
-> TcTypeEnv -> [LTyClDecl GhcRn] -> TcTypeEnv
forall (t :: * -> *) a b.
Foldable t =>
(a -> b -> b) -> b -> t a -> b
foldr (TcTypeEnv -> TcTypeEnv -> TcTypeEnv
forall a. NameEnv a -> NameEnv a -> NameEnv a
plusNameEnv (TcTypeEnv -> TcTypeEnv -> TcTypeEnv)
-> (LTyClDecl GhcRn -> TcTypeEnv)
-> LTyClDecl GhcRn
-> TcTypeEnv
-> TcTypeEnv
forall b c a. (b -> c) -> (a -> b) -> a -> c
. TyClDecl GhcRn -> TcTypeEnv
mk_prom_err_env (TyClDecl GhcRn -> TcTypeEnv)
-> (LTyClDecl GhcRn -> TyClDecl GhcRn)
-> LTyClDecl GhcRn
-> TcTypeEnv
forall b c a. (b -> c) -> (a -> b) -> a -> c
. LTyClDecl GhcRn -> TyClDecl GhcRn
forall l e. GenLocated l e -> e
unLoc)
          TcTypeEnv
forall a. NameEnv a
emptyNameEnv [LTyClDecl GhcRn]
decls

mk_prom_err_env :: TyClDecl GhcRn -> TcTypeEnv
mk_prom_err_env :: TyClDecl GhcRn -> TcTypeEnv
mk_prom_err_env (ClassDecl { tcdLName :: forall pass. TyClDecl pass -> Located (IdP pass)
tcdLName = L SrcSpan
_ IdP GhcRn
nm, tcdATs :: forall pass. TyClDecl pass -> [LFamilyDecl pass]
tcdATs = [LFamilyDecl GhcRn]
ats })
  = Name -> TcTyThing -> TcTypeEnv
forall a. Name -> a -> NameEnv a
unitNameEnv Name
IdP GhcRn
nm (PromotionErr -> TcTyThing
APromotionErr PromotionErr
ClassPE)
    TcTypeEnv -> TcTypeEnv -> TcTypeEnv
forall a. NameEnv a -> NameEnv a -> NameEnv a
`plusNameEnv`
    [(Name, TcTyThing)] -> TcTypeEnv
forall a. [(Name, a)] -> NameEnv a
mkNameEnv [ (FamilyDecl GhcRn -> IdP GhcRn
forall (p :: Pass). FamilyDecl (GhcPass p) -> IdP (GhcPass p)
familyDeclName FamilyDecl GhcRn
at, PromotionErr -> TcTyThing
APromotionErr PromotionErr
TyConPE)
              | L SrcSpan
_ FamilyDecl GhcRn
at <- [LFamilyDecl GhcRn]
ats ]

mk_prom_err_env (DataDecl { tcdLName :: forall pass. TyClDecl pass -> Located (IdP pass)
tcdLName = L SrcSpan
_ IdP GhcRn
name
                          , tcdDataDefn :: forall pass. TyClDecl pass -> HsDataDefn pass
tcdDataDefn = HsDataDefn { dd_cons :: forall pass. HsDataDefn pass -> [LConDecl pass]
dd_cons = [LConDecl GhcRn]
cons } })
  = Name -> TcTyThing -> TcTypeEnv
forall a. Name -> a -> NameEnv a
unitNameEnv Name
IdP GhcRn
name (PromotionErr -> TcTyThing
APromotionErr PromotionErr
TyConPE)
    TcTypeEnv -> TcTypeEnv -> TcTypeEnv
forall a. NameEnv a -> NameEnv a -> NameEnv a
`plusNameEnv`
    [(Name, TcTyThing)] -> TcTypeEnv
forall a. [(Name, a)] -> NameEnv a
mkNameEnv [ (Name
con, PromotionErr -> TcTyThing
APromotionErr PromotionErr
RecDataConPE)
              | L SrcSpan
_ ConDecl GhcRn
con' <- [LConDecl GhcRn]
cons
              , L SrcSpan
_ Name
con  <- ConDecl GhcRn -> [Located Name]
getConNames ConDecl GhcRn
con' ]

mk_prom_err_env TyClDecl GhcRn
decl
  = Name -> TcTyThing -> TcTypeEnv
forall a. Name -> a -> NameEnv a
unitNameEnv (TyClDecl GhcRn -> IdP GhcRn
forall (p :: Pass). TyClDecl (GhcPass p) -> IdP (GhcPass p)
tcdName TyClDecl GhcRn
decl) (PromotionErr -> TcTyThing
APromotionErr PromotionErr
TyConPE)
    -- Works for family declarations too

--------------
inferInitialKinds :: [LTyClDecl GhcRn] -> TcM [TcTyCon]
-- Returns a TcTyCon for each TyCon bound by the decls,
-- each with its initial kind

inferInitialKinds :: [LTyClDecl GhcRn] -> IOEnv (Env TcGblEnv TcLclEnv) [TyCon]
inferInitialKinds [LTyClDecl GhcRn]
decls
  = do { String -> SDoc -> TcRn ()
traceTc String
"inferInitialKinds {" (SDoc -> TcRn ()) -> SDoc -> TcRn ()
forall a b. (a -> b) -> a -> b
$ [Name] -> SDoc
forall a. Outputable a => a -> SDoc
ppr ((LTyClDecl GhcRn -> Name) -> [LTyClDecl GhcRn] -> [Name]
forall a b. (a -> b) -> [a] -> [b]
map (TyClDecl GhcRn -> Name
forall (p :: Pass). TyClDecl (GhcPass p) -> IdP (GhcPass p)
tcdName (TyClDecl GhcRn -> Name)
-> (LTyClDecl GhcRn -> TyClDecl GhcRn) -> LTyClDecl GhcRn -> Name
forall b c a. (b -> c) -> (a -> b) -> a -> c
. LTyClDecl GhcRn -> TyClDecl GhcRn
forall l e. GenLocated l e -> e
unLoc) [LTyClDecl GhcRn]
decls)
       ; [TyCon]
tcs <- (LTyClDecl GhcRn -> IOEnv (Env TcGblEnv TcLclEnv) [TyCon])
-> [LTyClDecl GhcRn] -> IOEnv (Env TcGblEnv TcLclEnv) [TyCon]
forall (m :: * -> *) a b. Monad m => (a -> m [b]) -> [a] -> m [b]
concatMapM LTyClDecl GhcRn -> IOEnv (Env TcGblEnv TcLclEnv) [TyCon]
infer_initial_kind [LTyClDecl GhcRn]
decls
       ; String -> SDoc -> TcRn ()
traceTc String
"inferInitialKinds done }" SDoc
empty
       ; [TyCon] -> IOEnv (Env TcGblEnv TcLclEnv) [TyCon]
forall (m :: * -> *) a. Monad m => a -> m a
return [TyCon]
tcs }
  where
    infer_initial_kind :: LTyClDecl GhcRn -> IOEnv (Env TcGblEnv TcLclEnv) [TyCon]
infer_initial_kind = (TyClDecl GhcRn -> IOEnv (Env TcGblEnv TcLclEnv) [TyCon])
-> LTyClDecl GhcRn -> IOEnv (Env TcGblEnv TcLclEnv) [TyCon]
forall a b. (a -> TcM b) -> Located a -> TcM b
addLocM (InitialKindStrategy
-> TyClDecl GhcRn -> IOEnv (Env TcGblEnv TcLclEnv) [TyCon]
getInitialKind InitialKindStrategy
InitialKindInfer)

-- Check type/class declarations against their standalone kind signatures or
-- CUSKs, producing a generalized TcTyCon for each.
checkInitialKinds :: [(LTyClDecl GhcRn, SAKS_or_CUSK)] -> TcM [TcTyCon]
checkInitialKinds :: [(LTyClDecl GhcRn, SAKS_or_CUSK)]
-> IOEnv (Env TcGblEnv TcLclEnv) [TyCon]
checkInitialKinds [(LTyClDecl GhcRn, SAKS_or_CUSK)]
decls
  = do { String -> SDoc -> TcRn ()
traceTc String
"checkInitialKinds {" (SDoc -> TcRn ()) -> SDoc -> TcRn ()
forall a b. (a -> b) -> a -> b
$ [(Name, SAKS_or_CUSK)] -> SDoc
forall a. Outputable a => a -> SDoc
ppr ((LTyClDecl GhcRn -> Name)
-> [(LTyClDecl GhcRn, SAKS_or_CUSK)] -> [(Name, SAKS_or_CUSK)]
forall a c b. (a -> c) -> [(a, b)] -> [(c, b)]
mapFst (TyClDecl GhcRn -> Name
forall (p :: Pass). TyClDecl (GhcPass p) -> IdP (GhcPass p)
tcdName (TyClDecl GhcRn -> Name)
-> (LTyClDecl GhcRn -> TyClDecl GhcRn) -> LTyClDecl GhcRn -> Name
forall b c a. (b -> c) -> (a -> b) -> a -> c
. LTyClDecl GhcRn -> TyClDecl GhcRn
forall l e. GenLocated l e -> e
unLoc) [(LTyClDecl GhcRn, SAKS_or_CUSK)]
decls)
       ; [TyCon]
tcs <- ((LTyClDecl GhcRn, SAKS_or_CUSK)
 -> IOEnv (Env TcGblEnv TcLclEnv) [TyCon])
-> [(LTyClDecl GhcRn, SAKS_or_CUSK)]
-> IOEnv (Env TcGblEnv TcLclEnv) [TyCon]
forall (m :: * -> *) a b. Monad m => (a -> m [b]) -> [a] -> m [b]
concatMapM (LTyClDecl GhcRn, SAKS_or_CUSK)
-> IOEnv (Env TcGblEnv TcLclEnv) [TyCon]
check_initial_kind [(LTyClDecl GhcRn, SAKS_or_CUSK)]
decls
       ; String -> SDoc -> TcRn ()
traceTc String
"checkInitialKinds done }" SDoc
empty
       ; [TyCon] -> IOEnv (Env TcGblEnv TcLclEnv) [TyCon]
forall (m :: * -> *) a. Monad m => a -> m a
return [TyCon]
tcs }
  where
    check_initial_kind :: (LTyClDecl GhcRn, SAKS_or_CUSK)
-> IOEnv (Env TcGblEnv TcLclEnv) [TyCon]
check_initial_kind (LTyClDecl GhcRn
ldecl, SAKS_or_CUSK
msig) =
      (TyClDecl GhcRn -> IOEnv (Env TcGblEnv TcLclEnv) [TyCon])
-> LTyClDecl GhcRn -> IOEnv (Env TcGblEnv TcLclEnv) [TyCon]
forall a b. (a -> TcM b) -> Located a -> TcM b
addLocM (InitialKindStrategy
-> TyClDecl GhcRn -> IOEnv (Env TcGblEnv TcLclEnv) [TyCon]
getInitialKind (SAKS_or_CUSK -> InitialKindStrategy
InitialKindCheck SAKS_or_CUSK
msig)) LTyClDecl GhcRn
ldecl

-- | Get the initial kind of a TyClDecl, either generalized or non-generalized,
-- depending on the 'InitialKindStrategy'.
getInitialKind :: InitialKindStrategy -> TyClDecl GhcRn -> TcM [TcTyCon]

-- Allocate a fresh kind variable for each TyCon and Class
-- For each tycon, return a TcTyCon with kind k
-- where k is the kind of tc, derived from the LHS
--         of the definition (and probably including
--         kind unification variables)
--      Example: data T a b = ...
--      return (T, kv1 -> kv2 -> kv3)
--
-- This pass deals with (ie incorporates into the kind it produces)
--   * The kind signatures on type-variable binders
--   * The result kinds signature on a TyClDecl
--
-- No family instances are passed to checkInitialKinds/inferInitialKinds
getInitialKind :: InitialKindStrategy
-> TyClDecl GhcRn -> IOEnv (Env TcGblEnv TcLclEnv) [TyCon]
getInitialKind InitialKindStrategy
strategy
    (ClassDecl { tcdLName :: forall pass. TyClDecl pass -> Located (IdP pass)
tcdLName = L SrcSpan
_ IdP GhcRn
name
               , tcdTyVars :: forall pass. TyClDecl pass -> LHsQTyVars pass
tcdTyVars = LHsQTyVars GhcRn
ktvs
               , tcdATs :: forall pass. TyClDecl pass -> [LFamilyDecl pass]
tcdATs = [LFamilyDecl GhcRn]
ats })
  = do { TyCon
cls <- InitialKindStrategy
-> Name
-> TyConFlavour
-> LHsQTyVars GhcRn
-> TcM ContextKind
-> TcRn TyCon
kcDeclHeader InitialKindStrategy
strategy Name
IdP GhcRn
name TyConFlavour
ClassFlavour LHsQTyVars GhcRn
ktvs (TcM ContextKind -> TcRn TyCon) -> TcM ContextKind -> TcRn TyCon
forall a b. (a -> b) -> a -> b
$
                ContextKind -> TcM ContextKind
forall (m :: * -> *) a. Monad m => a -> m a
return (Type -> ContextKind
TheKind Type
constraintKind)
       ; let parent_tv_prs :: [(Name, TyVar)]
parent_tv_prs = TyCon -> [(Name, TyVar)]
tcTyConScopedTyVars TyCon
cls
            -- See Note [Don't process associated types in getInitialKind]
       ; [TyCon]
inner_tcs <-
           [(Name, TyVar)]
-> IOEnv (Env TcGblEnv TcLclEnv) [TyCon]
-> IOEnv (Env TcGblEnv TcLclEnv) [TyCon]
forall r. [(Name, TyVar)] -> TcM r -> TcM r
tcExtendNameTyVarEnv [(Name, TyVar)]
parent_tv_prs (IOEnv (Env TcGblEnv TcLclEnv) [TyCon]
 -> IOEnv (Env TcGblEnv TcLclEnv) [TyCon])
-> IOEnv (Env TcGblEnv TcLclEnv) [TyCon]
-> IOEnv (Env TcGblEnv TcLclEnv) [TyCon]
forall a b. (a -> b) -> a -> b
$
           (LFamilyDecl GhcRn -> TcRn TyCon)
-> [LFamilyDecl GhcRn] -> IOEnv (Env TcGblEnv TcLclEnv) [TyCon]
forall (t :: * -> *) (m :: * -> *) a b.
(Traversable t, Monad m) =>
(a -> m b) -> t a -> m (t b)
mapM ((FamilyDecl GhcRn -> TcRn TyCon) -> LFamilyDecl GhcRn -> TcRn TyCon
forall a b. (a -> TcM b) -> Located a -> TcM b
addLocM (TyCon -> FamilyDecl GhcRn -> TcRn TyCon
getAssocFamInitialKind TyCon
cls)) [LFamilyDecl GhcRn]
ats
       ; [TyCon] -> IOEnv (Env TcGblEnv TcLclEnv) [TyCon]
forall (m :: * -> *) a. Monad m => a -> m a
return (TyCon
cls TyCon -> [TyCon] -> [TyCon]
forall a. a -> [a] -> [a]
: [TyCon]
inner_tcs) }
  where
    getAssocFamInitialKind :: TyCon -> FamilyDecl GhcRn -> TcRn TyCon
getAssocFamInitialKind TyCon
cls =
      case InitialKindStrategy
strategy of
        InitialKindStrategy
InitialKindInfer -> Maybe TyCon -> FamilyDecl GhcRn -> TcRn TyCon
get_fam_decl_initial_kind (TyCon -> Maybe TyCon
forall a. a -> Maybe a
Just TyCon
cls)
        InitialKindCheck SAKS_or_CUSK
_ -> TyCon -> FamilyDecl GhcRn -> TcRn TyCon
check_initial_kind_assoc_fam TyCon
cls

getInitialKind InitialKindStrategy
strategy
    (DataDecl { tcdLName :: forall pass. TyClDecl pass -> Located (IdP pass)
tcdLName = L SrcSpan
_ IdP GhcRn
name
              , tcdTyVars :: forall pass. TyClDecl pass -> LHsQTyVars pass
tcdTyVars = LHsQTyVars GhcRn
ktvs
              , tcdDataDefn :: forall pass. TyClDecl pass -> HsDataDefn pass
tcdDataDefn = HsDataDefn { dd_kindSig :: forall pass. HsDataDefn pass -> Maybe (LHsKind pass)
dd_kindSig = Maybe (LHsType GhcRn)
m_sig
                                         , dd_ND :: forall pass. HsDataDefn pass -> NewOrData
dd_ND = NewOrData
new_or_data } })
  = do  { let flav :: TyConFlavour
flav = NewOrData -> TyConFlavour
newOrDataToFlavour NewOrData
new_or_data
              ctxt :: UserTypeCtxt
ctxt = Name -> UserTypeCtxt
DataKindCtxt Name
IdP GhcRn
name
        ; TyCon
tc <- InitialKindStrategy
-> Name
-> TyConFlavour
-> LHsQTyVars GhcRn
-> TcM ContextKind
-> TcRn TyCon
kcDeclHeader InitialKindStrategy
strategy Name
IdP GhcRn
name TyConFlavour
flav LHsQTyVars GhcRn
ktvs (TcM ContextKind -> TcRn TyCon) -> TcM ContextKind -> TcRn TyCon
forall a b. (a -> b) -> a -> b
$
                case Maybe (LHsType GhcRn)
m_sig of
                  Just LHsType GhcRn
ksig -> Type -> ContextKind
TheKind (Type -> ContextKind) -> TcM Type -> TcM ContextKind
forall (f :: * -> *) a b. Functor f => (a -> b) -> f a -> f b
<$> UserTypeCtxt -> LHsType GhcRn -> TcM Type
tcLHsKindSig UserTypeCtxt
ctxt LHsType GhcRn
ksig
                  Maybe (LHsType GhcRn)
Nothing -> ContextKind -> TcM ContextKind
forall (m :: * -> *) a. Monad m => a -> m a
return (ContextKind -> TcM ContextKind) -> ContextKind -> TcM ContextKind
forall a b. (a -> b) -> a -> b
$ NewOrData -> ContextKind
dataDeclDefaultResultKind NewOrData
new_or_data
        ; [TyCon] -> IOEnv (Env TcGblEnv TcLclEnv) [TyCon]
forall (m :: * -> *) a. Monad m => a -> m a
return [TyCon
tc] }

getInitialKind InitialKindStrategy
InitialKindInfer (FamDecl { tcdFam :: forall pass. TyClDecl pass -> FamilyDecl pass
tcdFam = FamilyDecl GhcRn
decl })
  = do { TyCon
tc <- Maybe TyCon -> FamilyDecl GhcRn -> TcRn TyCon
get_fam_decl_initial_kind Maybe TyCon
forall a. Maybe a
Nothing FamilyDecl GhcRn
decl
       ; [TyCon] -> IOEnv (Env TcGblEnv TcLclEnv) [TyCon]
forall (m :: * -> *) a. Monad m => a -> m a
return [TyCon
tc] }

getInitialKind (InitialKindCheck SAKS_or_CUSK
msig) (FamDecl { tcdFam :: forall pass. TyClDecl pass -> FamilyDecl pass
tcdFam =
  FamilyDecl { fdLName :: forall pass. FamilyDecl pass -> Located (IdP pass)
fdLName     = GenLocated SrcSpan (IdP GhcRn) -> Name
forall l e. GenLocated l e -> e
unLoc -> Name
name
             , fdTyVars :: forall pass. FamilyDecl pass -> LHsQTyVars pass
fdTyVars    = LHsQTyVars GhcRn
ktvs
             , fdResultSig :: forall pass. FamilyDecl pass -> LFamilyResultSig pass
fdResultSig = LFamilyResultSig GhcRn -> FamilyResultSig GhcRn
forall l e. GenLocated l e -> e
unLoc -> FamilyResultSig GhcRn
resultSig
             , fdInfo :: forall pass. FamilyDecl pass -> FamilyInfo pass
fdInfo      = FamilyInfo GhcRn
info } } )
  = do { let flav :: TyConFlavour
flav = Maybe TyCon -> FamilyInfo GhcRn -> TyConFlavour
forall pass. Maybe TyCon -> FamilyInfo pass -> TyConFlavour
getFamFlav Maybe TyCon
forall a. Maybe a
Nothing FamilyInfo GhcRn
info
             ctxt :: UserTypeCtxt
ctxt = Name -> UserTypeCtxt
TyFamResKindCtxt Name
name
       ; TyCon
tc <- InitialKindStrategy
-> Name
-> TyConFlavour
-> LHsQTyVars GhcRn
-> TcM ContextKind
-> TcRn TyCon
kcDeclHeader (SAKS_or_CUSK -> InitialKindStrategy
InitialKindCheck SAKS_or_CUSK
msig) Name
name TyConFlavour
flav LHsQTyVars GhcRn
ktvs (TcM ContextKind -> TcRn TyCon) -> TcM ContextKind -> TcRn TyCon
forall a b. (a -> b) -> a -> b
$
               case FamilyResultSig GhcRn -> Maybe (LHsType GhcRn)
forall (p :: Pass).
FamilyResultSig (GhcPass p) -> Maybe (LHsKind (GhcPass p))
famResultKindSignature FamilyResultSig GhcRn
resultSig of
                 Just LHsType GhcRn
ksig -> Type -> ContextKind
TheKind (Type -> ContextKind) -> TcM Type -> TcM ContextKind
forall (f :: * -> *) a b. Functor f => (a -> b) -> f a -> f b
<$> UserTypeCtxt -> LHsType GhcRn -> TcM Type
tcLHsKindSig UserTypeCtxt
ctxt LHsType GhcRn
ksig
                 Maybe (LHsType GhcRn)
Nothing ->
                   case SAKS_or_CUSK
msig of
                     SAKS_or_CUSK
CUSK -> ContextKind -> TcM ContextKind
forall (m :: * -> *) a. Monad m => a -> m a
return (Type -> ContextKind
TheKind Type
liftedTypeKind)
                     SAKS Type
_ -> ContextKind -> TcM ContextKind
forall (m :: * -> *) a. Monad m => a -> m a
return ContextKind
AnyKind
       ; [TyCon] -> IOEnv (Env TcGblEnv TcLclEnv) [TyCon]
forall (m :: * -> *) a. Monad m => a -> m a
return [TyCon
tc] }

getInitialKind InitialKindStrategy
strategy
    (SynDecl { tcdLName :: forall pass. TyClDecl pass -> Located (IdP pass)
tcdLName = L SrcSpan
_ IdP GhcRn
name
             , tcdTyVars :: forall pass. TyClDecl pass -> LHsQTyVars pass
tcdTyVars = LHsQTyVars GhcRn
ktvs
             , tcdRhs :: forall pass. TyClDecl pass -> LHsType pass
tcdRhs = LHsType GhcRn
rhs })
  = do { let ctxt :: UserTypeCtxt
ctxt = Name -> UserTypeCtxt
TySynKindCtxt Name
IdP GhcRn
name
       ; TyCon
tc <- InitialKindStrategy
-> Name
-> TyConFlavour
-> LHsQTyVars GhcRn
-> TcM ContextKind
-> TcRn TyCon
kcDeclHeader InitialKindStrategy
strategy Name
IdP GhcRn
name TyConFlavour
TypeSynonymFlavour LHsQTyVars GhcRn
ktvs (TcM ContextKind -> TcRn TyCon) -> TcM ContextKind -> TcRn TyCon
forall a b. (a -> b) -> a -> b
$
               case LHsType GhcRn -> Maybe (LHsType GhcRn)
forall pass. LHsType pass -> Maybe (LHsType pass)
hsTyKindSig LHsType GhcRn
rhs of
                 Just LHsType GhcRn
rhs_sig -> Type -> ContextKind
TheKind (Type -> ContextKind) -> TcM Type -> TcM ContextKind
forall (f :: * -> *) a b. Functor f => (a -> b) -> f a -> f b
<$> UserTypeCtxt -> LHsType GhcRn -> TcM Type
tcLHsKindSig UserTypeCtxt
ctxt LHsType GhcRn
rhs_sig
                 Maybe (LHsType GhcRn)
Nothing -> ContextKind -> TcM ContextKind
forall (m :: * -> *) a. Monad m => a -> m a
return ContextKind
AnyKind
       ; [TyCon] -> IOEnv (Env TcGblEnv TcLclEnv) [TyCon]
forall (m :: * -> *) a. Monad m => a -> m a
return [TyCon
tc] }

get_fam_decl_initial_kind
  :: Maybe TcTyCon -- ^ Just cls <=> this is an associated family of class cls
  -> FamilyDecl GhcRn
  -> TcM TcTyCon
get_fam_decl_initial_kind :: Maybe TyCon -> FamilyDecl GhcRn -> TcRn TyCon
get_fam_decl_initial_kind Maybe TyCon
mb_parent_tycon
    FamilyDecl { fdLName :: forall pass. FamilyDecl pass -> Located (IdP pass)
fdLName     = L SrcSpan
_ IdP GhcRn
name
               , fdTyVars :: forall pass. FamilyDecl pass -> LHsQTyVars pass
fdTyVars    = LHsQTyVars GhcRn
ktvs
               , fdResultSig :: forall pass. FamilyDecl pass -> LFamilyResultSig pass
fdResultSig = L SrcSpan
_ FamilyResultSig GhcRn
resultSig
               , fdInfo :: forall pass. FamilyDecl pass -> FamilyInfo pass
fdInfo      = FamilyInfo GhcRn
info }
  = InitialKindStrategy
-> Name
-> TyConFlavour
-> LHsQTyVars GhcRn
-> TcM ContextKind
-> TcRn TyCon
kcDeclHeader InitialKindStrategy
InitialKindInfer Name
IdP GhcRn
name TyConFlavour
flav LHsQTyVars GhcRn
ktvs (TcM ContextKind -> TcRn TyCon) -> TcM ContextKind -> TcRn TyCon
forall a b. (a -> b) -> a -> b
$
    case FamilyResultSig GhcRn
resultSig of
      KindSig XCKindSig GhcRn
_ LHsType GhcRn
ki                            -> Type -> ContextKind
TheKind (Type -> ContextKind) -> TcM Type -> TcM ContextKind
forall (f :: * -> *) a b. Functor f => (a -> b) -> f a -> f b
<$> UserTypeCtxt -> LHsType GhcRn -> TcM Type
tcLHsKindSig UserTypeCtxt
ctxt LHsType GhcRn
ki
      TyVarSig XTyVarSig GhcRn
_ (L SrcSpan
_ (KindedTyVar XKindedTyVar GhcRn
_ ()
_ GenLocated SrcSpan (IdP GhcRn)
_ LHsType GhcRn
ki)) -> Type -> ContextKind
TheKind (Type -> ContextKind) -> TcM Type -> TcM ContextKind
forall (f :: * -> *) a b. Functor f => (a -> b) -> f a -> f b
<$> UserTypeCtxt -> LHsType GhcRn -> TcM Type
tcLHsKindSig UserTypeCtxt
ctxt LHsType GhcRn
ki
      FamilyResultSig GhcRn
_ -- open type families have * return kind by default
        | TyConFlavour -> Bool
tcFlavourIsOpen TyConFlavour
flav              -> ContextKind -> TcM ContextKind
forall (m :: * -> *) a. Monad m => a -> m a
return (Type -> ContextKind
TheKind Type
liftedTypeKind)
               -- closed type families have their return kind inferred
               -- by default
        | Bool
otherwise                         -> ContextKind -> TcM ContextKind
forall (m :: * -> *) a. Monad m => a -> m a
return ContextKind
AnyKind
  where
    flav :: TyConFlavour
flav = Maybe TyCon -> FamilyInfo GhcRn -> TyConFlavour
forall pass. Maybe TyCon -> FamilyInfo pass -> TyConFlavour
getFamFlav Maybe TyCon
mb_parent_tycon FamilyInfo GhcRn
info
    ctxt :: UserTypeCtxt
ctxt = Name -> UserTypeCtxt
TyFamResKindCtxt Name
IdP GhcRn
name

-- See Note [Standalone kind signatures for associated types]
check_initial_kind_assoc_fam
  :: TcTyCon -- parent class
  -> FamilyDecl GhcRn
  -> TcM TcTyCon
check_initial_kind_assoc_fam :: TyCon -> FamilyDecl GhcRn -> TcRn TyCon
check_initial_kind_assoc_fam TyCon
cls
  FamilyDecl
    { fdLName :: forall pass. FamilyDecl pass -> Located (IdP pass)
fdLName     = GenLocated SrcSpan (IdP GhcRn) -> Name
forall l e. GenLocated l e -> e
unLoc -> Name
name
    , fdTyVars :: forall pass. FamilyDecl pass -> LHsQTyVars pass
fdTyVars    = LHsQTyVars GhcRn
ktvs
    , fdResultSig :: forall pass. FamilyDecl pass -> LFamilyResultSig pass
fdResultSig = LFamilyResultSig GhcRn -> FamilyResultSig GhcRn
forall l e. GenLocated l e -> e
unLoc -> FamilyResultSig GhcRn
resultSig
    , fdInfo :: forall pass. FamilyDecl pass -> FamilyInfo pass
fdInfo      = FamilyInfo GhcRn
info }
  = InitialKindStrategy
-> Name
-> TyConFlavour
-> LHsQTyVars GhcRn
-> TcM ContextKind
-> TcRn TyCon
kcDeclHeader (SAKS_or_CUSK -> InitialKindStrategy
InitialKindCheck SAKS_or_CUSK
CUSK) Name
name TyConFlavour
flav LHsQTyVars GhcRn
ktvs (TcM ContextKind -> TcRn TyCon) -> TcM ContextKind -> TcRn TyCon
forall a b. (a -> b) -> a -> b
$
    case FamilyResultSig GhcRn -> Maybe (LHsType GhcRn)
forall (p :: Pass).
FamilyResultSig (GhcPass p) -> Maybe (LHsKind (GhcPass p))
famResultKindSignature FamilyResultSig GhcRn
resultSig of
      Just LHsType GhcRn
ksig -> Type -> ContextKind
TheKind (Type -> ContextKind) -> TcM Type -> TcM ContextKind
forall (f :: * -> *) a b. Functor f => (a -> b) -> f a -> f b
<$> UserTypeCtxt -> LHsType GhcRn -> TcM Type
tcLHsKindSig UserTypeCtxt
ctxt LHsType GhcRn
ksig
      Maybe (LHsType GhcRn)
Nothing -> ContextKind -> TcM ContextKind
forall (m :: * -> *) a. Monad m => a -> m a
return (Type -> ContextKind
TheKind Type
liftedTypeKind)
  where
    ctxt :: UserTypeCtxt
ctxt = Name -> UserTypeCtxt
TyFamResKindCtxt Name
name
    flav :: TyConFlavour
flav = Maybe TyCon -> FamilyInfo GhcRn -> TyConFlavour
forall pass. Maybe TyCon -> FamilyInfo pass -> TyConFlavour
getFamFlav (TyCon -> Maybe TyCon
forall a. a -> Maybe a
Just TyCon
cls) FamilyInfo GhcRn
info

{- Note [Standalone kind signatures for associated types]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

If associated types had standalone kind signatures, would they wear them

---------------------------+------------------------------
  like this? (OUT)         |   or like this? (IN)
---------------------------+------------------------------
  type T :: Type -> Type   |   class C a where
  class C a where          |     type T :: Type -> Type
    type T a               |     type T a

The (IN) variant is syntactically ambiguous:

  class C a where
    type T :: a   -- standalone kind signature?
    type T :: a   -- declaration header?

The (OUT) variant does not suffer from this issue, but it might not be the
direction in which we want to take Haskell: we seek to unify type families and
functions, and, by extension, associated types with class methods. And yet we
give class methods their signatures inside the class, not outside. Neither do
we have the counterpart of InstanceSigs for StandaloneKindSignatures.

For now, we dodge the question by using CUSKs for associated types instead of
standalone kind signatures. This is a simple addition to the rule we used to
have before standalone kind signatures:

  old rule:  associated type has a CUSK iff its parent class has a CUSK
  new rule:  associated type has a CUSK iff its parent class has a CUSK or a standalone kind signature

-}

-- See Note [Data declaration default result kind]
dataDeclDefaultResultKind :: NewOrData -> ContextKind
dataDeclDefaultResultKind :: NewOrData -> ContextKind
dataDeclDefaultResultKind NewOrData
NewType  = ContextKind
OpenKind
  -- See Note [Implementation of UnliftedNewtypes], point <Error Messages>.
dataDeclDefaultResultKind NewOrData
DataType = Type -> ContextKind
TheKind Type
liftedTypeKind

{- Note [Data declaration default result kind]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

When the user has not written an inline result kind annotation on a data
declaration, we assume it to be 'Type'. That is, the following declarations
D1 and D2 are considered equivalent:

  data D1         where ...
  data D2 :: Type where ...

The consequence of this assumption is that we reject D3 even though we
accept D4:

  data D3 where
    MkD3 :: ... -> D3 param

  data D4 :: Type -> Type where
    MkD4 :: ... -> D4 param

However, there's a twist: for newtypes, we must relax
the assumed result kind to (TYPE r):

  newtype D5 where
    MkD5 :: Int# -> D5

See Note [Implementation of UnliftedNewtypes], STEP 1 and it's sub-note
<Error Messages>.
-}

---------------------------------
getFamFlav
  :: Maybe TcTyCon    -- ^ Just cls <=> this is an associated family of class cls
  -> FamilyInfo pass
  -> TyConFlavour
getFamFlav :: forall pass. Maybe TyCon -> FamilyInfo pass -> TyConFlavour
getFamFlav Maybe TyCon
mb_parent_tycon FamilyInfo pass
info =
  case FamilyInfo pass
info of
    FamilyInfo pass
DataFamily         -> Maybe TyCon -> TyConFlavour
DataFamilyFlavour Maybe TyCon
mb_parent_tycon
    FamilyInfo pass
OpenTypeFamily     -> Maybe TyCon -> TyConFlavour
OpenTypeFamilyFlavour Maybe TyCon
mb_parent_tycon
    ClosedTypeFamily Maybe [LTyFamInstEqn pass]
_ -> ASSERT( isNothing mb_parent_tycon ) -- See Note [Closed type family mb_parent_tycon]
                          TyConFlavour
ClosedTypeFamilyFlavour

{- Note [Closed type family mb_parent_tycon]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
There's no way to write a closed type family inside a class declaration:

  class C a where
    type family F a where  -- error: parse error on input ‘where’

In fact, it is not clear what the meaning of such a declaration would be.
Therefore, 'mb_parent_tycon' of any closed type family has to be Nothing.
-}

------------------------------------------------------------------------
kcLTyClDecl :: LTyClDecl GhcRn -> TcM ()
  -- See Note [Kind checking for type and class decls]
  -- Called only for declarations without a signature (no CUSKs or SAKs here)
kcLTyClDecl :: LTyClDecl GhcRn -> TcRn ()
kcLTyClDecl (L SrcSpan
loc TyClDecl GhcRn
decl)
  = SrcSpan -> TcRn () -> TcRn ()
forall a. SrcSpan -> TcRn a -> TcRn a
setSrcSpan SrcSpan
loc (TcRn () -> TcRn ()) -> TcRn () -> TcRn ()
forall a b. (a -> b) -> a -> b
$
    do { TyCon
tycon <- HasDebugCallStack => Name -> TcRn TyCon
Name -> TcRn TyCon
tcLookupTcTyCon Name
IdP GhcRn
tc_name
       ; String -> SDoc -> TcRn ()
traceTc String
"kcTyClDecl {" (Name -> SDoc
forall a. Outputable a => a -> SDoc
ppr Name
IdP GhcRn
tc_name)
       ; TyCon -> TcRn () -> TcRn ()
forall a. TyCon -> TcM a -> TcM a
addVDQNote TyCon
tycon (TcRn () -> TcRn ()) -> TcRn () -> TcRn ()
forall a b. (a -> b) -> a -> b
$   -- See Note [Inferring visible dependent quantification]
         SDoc -> TcRn () -> TcRn ()
forall a. SDoc -> TcM a -> TcM a
addErrCtxt (TyClDecl GhcRn -> SDoc
tcMkDeclCtxt TyClDecl GhcRn
decl) (TcRn () -> TcRn ()) -> TcRn () -> TcRn ()
forall a b. (a -> b) -> a -> b
$
         TyClDecl GhcRn -> TyCon -> TcRn ()
kcTyClDecl TyClDecl GhcRn
decl TyCon
tycon
       ; String -> SDoc -> TcRn ()
traceTc String
"kcTyClDecl done }" (Name -> SDoc
forall a. Outputable a => a -> SDoc
ppr Name
IdP GhcRn
tc_name) }
  where
    tc_name :: IdP GhcRn
tc_name = TyClDecl GhcRn -> IdP GhcRn
forall (p :: Pass). TyClDecl (GhcPass p) -> IdP (GhcPass p)
tcdName TyClDecl GhcRn
decl

kcTyClDecl :: TyClDecl GhcRn -> TcTyCon -> TcM ()
-- This function is used solely for its side effect on kind variables
-- NB kind signatures on the type variables and
--    result kind signature have already been dealt with
--    by inferInitialKind, so we can ignore them here.

kcTyClDecl :: TyClDecl GhcRn -> TyCon -> TcRn ()
kcTyClDecl (DataDecl { tcdLName :: forall pass. TyClDecl pass -> Located (IdP pass)
tcdLName    = (L SrcSpan
_ IdP GhcRn
name)
                     , tcdDataDefn :: forall pass. TyClDecl pass -> HsDataDefn pass
tcdDataDefn = HsDataDefn GhcRn
defn }) TyCon
tyCon
  | HsDataDefn { dd_cons :: forall pass. HsDataDefn pass -> [LConDecl pass]
dd_cons = cons :: [LConDecl GhcRn]
cons@((L SrcSpan
_ (ConDeclGADT {})) : [LConDecl GhcRn]
_)
               , dd_ctxt :: forall pass. HsDataDefn pass -> LHsContext pass
dd_ctxt = (L SrcSpan
_ [])
               , dd_ND :: forall pass. HsDataDefn pass -> NewOrData
dd_ND = NewOrData
new_or_data } <- HsDataDefn GhcRn
defn
  = -- See Note [Implementation of UnliftedNewtypes] STEP 2
    NewOrData -> Type -> [LConDecl GhcRn] -> TcRn ()
kcConDecls NewOrData
new_or_data (TyCon -> Type
tyConResKind TyCon
tyCon) [LConDecl GhcRn]
cons

    -- hs_tvs and dd_kindSig already dealt with in inferInitialKind
    -- This must be a GADT-style decl,
    --        (see invariants of DataDefn declaration)
    -- so (a) we don't need to bring the hs_tvs into scope, because the
    --        ConDecls bind all their own variables
    --    (b) dd_ctxt is not allowed for GADT-style decls, so we can ignore it

  | HsDataDefn { dd_ctxt :: forall pass. HsDataDefn pass -> LHsContext pass
dd_ctxt = GenLocated SrcSpan (HsContext GhcRn)
ctxt
               , dd_cons :: forall pass. HsDataDefn pass -> [LConDecl pass]
dd_cons = [LConDecl GhcRn]
cons
               , dd_ND :: forall pass. HsDataDefn pass -> NewOrData
dd_ND = NewOrData
new_or_data } <- HsDataDefn GhcRn
defn
  = Name -> (TyCon -> [TyConBinder] -> Type -> TcRn ()) -> TcRn ()
forall a.
Name -> (TyCon -> [TyConBinder] -> Type -> TcM a) -> TcM a
bindTyClTyVars Name
IdP GhcRn
name ((TyCon -> [TyConBinder] -> Type -> TcRn ()) -> TcRn ())
-> (TyCon -> [TyConBinder] -> Type -> TcRn ()) -> TcRn ()
forall a b. (a -> b) -> a -> b
$ \ TyCon
_ [TyConBinder]
_ Type
_ ->
    do { [Type]
_ <- GenLocated SrcSpan (HsContext GhcRn) -> TcM [Type]
tcHsContext GenLocated SrcSpan (HsContext GhcRn)
ctxt
       ; NewOrData -> Type -> [LConDecl GhcRn] -> TcRn ()
kcConDecls NewOrData
new_or_data (TyCon -> Type
tyConResKind TyCon
tyCon) [LConDecl GhcRn]
cons
       }

kcTyClDecl (SynDecl { tcdLName :: forall pass. TyClDecl pass -> Located (IdP pass)
tcdLName = L SrcSpan
_ IdP GhcRn
name, tcdRhs :: forall pass. TyClDecl pass -> LHsType pass
tcdRhs = LHsType GhcRn
rhs }) TyCon
_tycon
  = Name -> (TyCon -> [TyConBinder] -> Type -> TcRn ()) -> TcRn ()
forall a.
Name -> (TyCon -> [TyConBinder] -> Type -> TcM a) -> TcM a
bindTyClTyVars Name
IdP GhcRn
name ((TyCon -> [TyConBinder] -> Type -> TcRn ()) -> TcRn ())
-> (TyCon -> [TyConBinder] -> Type -> TcRn ()) -> TcRn ()
forall a b. (a -> b) -> a -> b
$ \ TyCon
_ [TyConBinder]
_ Type
res_kind ->
    TcM Type -> TcRn ()
forall a. TcM a -> TcRn ()
discardResult (TcM Type -> TcRn ()) -> TcM Type -> TcRn ()
forall a b. (a -> b) -> a -> b
$ LHsType GhcRn -> ContextKind -> TcM Type
tcCheckLHsType LHsType GhcRn
rhs (Type -> ContextKind
TheKind Type
res_kind)
        -- NB: check against the result kind that we allocated
        -- in inferInitialKinds.

kcTyClDecl (ClassDecl { tcdLName :: forall pass. TyClDecl pass -> Located (IdP pass)
tcdLName = L SrcSpan
_ IdP GhcRn
name
                      , tcdCtxt :: forall pass. TyClDecl pass -> LHsContext pass
tcdCtxt = GenLocated SrcSpan (HsContext GhcRn)
ctxt, tcdSigs :: forall pass. TyClDecl pass -> [LSig pass]
tcdSigs = [LSig GhcRn]
sigs }) TyCon
_tycon
  = Name -> (TyCon -> [TyConBinder] -> Type -> TcRn ()) -> TcRn ()
forall a.
Name -> (TyCon -> [TyConBinder] -> Type -> TcM a) -> TcM a
bindTyClTyVars Name
IdP GhcRn
name ((TyCon -> [TyConBinder] -> Type -> TcRn ()) -> TcRn ())
-> (TyCon -> [TyConBinder] -> Type -> TcRn ()) -> TcRn ()
forall a b. (a -> b) -> a -> b
$ \ TyCon
_ [TyConBinder]
_ Type
_ ->
    do  { [Type]
_ <- GenLocated SrcSpan (HsContext GhcRn) -> TcM [Type]
tcHsContext GenLocated SrcSpan (HsContext GhcRn)
ctxt
        ; (LSig GhcRn -> TcRn ()) -> [LSig GhcRn] -> TcRn ()
forall (t :: * -> *) (m :: * -> *) a b.
(Foldable t, Monad m) =>
(a -> m b) -> t a -> m ()
mapM_ ((Sig GhcRn -> TcRn ()) -> LSig GhcRn -> TcRn ()
forall a. (a -> TcRn ()) -> Located a -> TcRn ()
wrapLocM_ Sig GhcRn -> TcRn ()
kc_sig) [LSig GhcRn]
sigs }
  where
    kc_sig :: Sig GhcRn -> TcRn ()
kc_sig (ClassOpSig XClassOpSig GhcRn
_ Bool
_ [GenLocated SrcSpan (IdP GhcRn)]
nms LHsSigType GhcRn
op_ty) = SkolemInfo -> [Located Name] -> LHsSigType GhcRn -> TcRn ()
kcClassSigType SkolemInfo
skol_info [Located Name]
[GenLocated SrcSpan (IdP GhcRn)]
nms LHsSigType GhcRn
op_ty
    kc_sig Sig GhcRn
_                          = () -> TcRn ()
forall (m :: * -> *) a. Monad m => a -> m a
return ()

    skol_info :: SkolemInfo
skol_info = TyConFlavour -> Name -> SkolemInfo
TyConSkol TyConFlavour
ClassFlavour Name
IdP GhcRn
name

kcTyClDecl (FamDecl XFamDecl GhcRn
_ (FamilyDecl { fdInfo :: forall pass. FamilyDecl pass -> FamilyInfo pass
fdInfo   = FamilyInfo GhcRn
fd_info })) TyCon
fam_tc
-- closed type families look at their equations, but other families don't
-- do anything here
  = case FamilyInfo GhcRn
fd_info of
      ClosedTypeFamily (Just [LTyFamInstEqn GhcRn]
eqns) -> (LTyFamInstEqn GhcRn -> TcRn ())
-> [LTyFamInstEqn GhcRn] -> TcRn ()
forall (t :: * -> *) (m :: * -> *) a b.
(Foldable t, Monad m) =>
(a -> m b) -> t a -> m ()
mapM_ (TyCon -> LTyFamInstEqn GhcRn -> TcRn ()
kcTyFamInstEqn TyCon
fam_tc) [LTyFamInstEqn GhcRn]
eqns
      FamilyInfo GhcRn
_ -> () -> TcRn ()
forall (m :: * -> *) a. Monad m => a -> m a
return ()

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

-- Type check the types of the arguments to a data constructor.
-- This includes doing kind unification if the type is a newtype.
-- See Note [Implementation of UnliftedNewtypes] for why we need
-- the first two arguments.
kcConArgTys :: NewOrData -> Kind -> [HsScaled GhcRn (LHsType GhcRn)] -> TcM ()
kcConArgTys :: NewOrData -> Type -> [HsScaled GhcRn (LHsType GhcRn)] -> TcRn ()
kcConArgTys NewOrData
new_or_data Type
res_kind [HsScaled GhcRn (LHsType GhcRn)]
arg_tys = do
  { let exp_kind :: ContextKind
exp_kind = NewOrData -> Type -> ContextKind
getArgExpKind NewOrData
new_or_data Type
res_kind
  ; [HsScaled GhcRn (LHsType GhcRn)]
-> (HsScaled GhcRn (LHsType GhcRn) -> TcM Type) -> TcRn ()
forall (t :: * -> *) (m :: * -> *) a b.
(Foldable t, Monad m) =>
t a -> (a -> m b) -> m ()
forM_ [HsScaled GhcRn (LHsType GhcRn)]
arg_tys (\(HsScaled HsArrow GhcRn
mult LHsType GhcRn
ty) -> do Type
_ <- LHsType GhcRn -> ContextKind -> TcM Type
tcCheckLHsType (LHsType GhcRn -> LHsType GhcRn
forall a. LHsType a -> LHsType a
getBangType LHsType GhcRn
ty) ContextKind
exp_kind
                                             HsArrow GhcRn -> TcM Type
tcMult HsArrow GhcRn
mult)

    -- See Note [Implementation of UnliftedNewtypes], STEP 2
  }

kcConDecls :: NewOrData
           -> Kind             -- The result kind signature
           -> [LConDecl GhcRn] -- The data constructors
           -> TcM ()
kcConDecls :: NewOrData -> Type -> [LConDecl GhcRn] -> TcRn ()
kcConDecls NewOrData
new_or_data Type
res_kind [LConDecl GhcRn]
cons
  = (LConDecl GhcRn -> TcRn ()) -> [LConDecl GhcRn] -> TcRn ()
forall (t :: * -> *) (m :: * -> *) a b.
(Foldable t, Monad m) =>
(a -> m b) -> t a -> m ()
mapM_ ((ConDecl GhcRn -> TcRn ()) -> LConDecl GhcRn -> TcRn ()
forall a. (a -> TcRn ()) -> Located a -> TcRn ()
wrapLocM_ (NewOrData -> Type -> ConDecl GhcRn -> TcRn ()
kcConDecl NewOrData
new_or_data Type
final_res_kind)) [LConDecl GhcRn]
cons
  where
    ([TyCoBinder]
_, Type
final_res_kind) = Type -> ([TyCoBinder], Type)
splitPiTys Type
res_kind
        -- See Note [kcConDecls result kind]

-- Kind check a data constructor. In additional to the data constructor,
-- we also need to know about whether or not its corresponding type was
-- declared with data or newtype, and we need to know the result kind of
-- this type. See Note [Implementation of UnliftedNewtypes] for why
-- we need the first two arguments.
kcConDecl :: NewOrData
          -> Kind  -- Result kind of the type constructor
                   -- Usually Type but can be TYPE UnliftedRep
                   -- or even TYPE r, in the case of unlifted newtype
          -> ConDecl GhcRn
          -> TcM ()
kcConDecl :: NewOrData -> Type -> ConDecl GhcRn -> TcRn ()
kcConDecl NewOrData
new_or_data Type
res_kind (ConDeclH98
  { con_name :: forall pass. ConDecl pass -> Located (IdP pass)
con_name = GenLocated SrcSpan (IdP GhcRn)
name, con_ex_tvs :: forall pass. ConDecl pass -> [LHsTyVarBndr Specificity pass]
con_ex_tvs = [LHsTyVarBndr Specificity GhcRn]
ex_tvs
  , con_mb_cxt :: forall pass. ConDecl pass -> Maybe (LHsContext pass)
con_mb_cxt = Maybe (GenLocated SrcSpan (HsContext GhcRn))
ex_ctxt, con_args :: forall pass. ConDecl pass -> HsConDeclDetails pass
con_args = HsConDeclDetails GhcRn
args })
  = SDoc -> TcRn () -> TcRn ()
forall a. SDoc -> TcM a -> TcM a
addErrCtxt ([Located Name] -> SDoc
dataConCtxtName [Located Name
GenLocated SrcSpan (IdP GhcRn)
name]) (TcRn () -> TcRn ()) -> TcRn () -> TcRn ()
forall a b. (a -> b) -> a -> b
$
    TcM ([VarBndr TyVar Specificity], ()) -> TcRn ()
forall a. TcM a -> TcRn ()
discardResult                   (TcM ([VarBndr TyVar Specificity], ()) -> TcRn ())
-> TcM ([VarBndr TyVar Specificity], ()) -> TcRn ()
forall a b. (a -> b) -> a -> b
$
    [LHsTyVarBndr Specificity GhcRn]
-> TcRn () -> TcM ([VarBndr TyVar Specificity], ())
forall flag a.
OutputableBndrFlag flag =>
[LHsTyVarBndr flag GhcRn] -> TcM a -> TcM ([VarBndr TyVar flag], a)
bindExplicitTKBndrs_Tv [LHsTyVarBndr Specificity GhcRn]
ex_tvs (TcRn () -> TcM ([VarBndr TyVar Specificity], ()))
-> TcRn () -> TcM ([VarBndr TyVar Specificity], ())
forall a b. (a -> b) -> a -> b
$
    do { [Type]
_ <- Maybe (GenLocated SrcSpan (HsContext GhcRn)) -> TcM [Type]
tcHsMbContext Maybe (GenLocated SrcSpan (HsContext GhcRn))
ex_ctxt
       ; NewOrData -> Type -> [HsScaled GhcRn (LHsType GhcRn)] -> TcRn ()
kcConArgTys NewOrData
new_or_data Type
res_kind (HsConDeclDetails GhcRn -> [HsScaled GhcRn (LHsType GhcRn)]
forall pass.
HsConDeclDetails pass -> [HsScaled pass (LBangType pass)]
hsConDeclArgTys HsConDeclDetails GhcRn
args)
         -- We don't need to check the telescope here,
         -- because that's done in tcConDecl
       }

kcConDecl NewOrData
new_or_data Type
res_kind (ConDeclGADT
    { con_names :: forall pass. ConDecl pass -> [Located (IdP pass)]
con_names = [GenLocated SrcSpan (IdP GhcRn)]
names, con_qvars :: forall pass. ConDecl pass -> [LHsTyVarBndr Specificity pass]
con_qvars = [LHsTyVarBndr Specificity GhcRn]
explicit_tkv_nms, con_mb_cxt :: forall pass. ConDecl pass -> Maybe (LHsContext pass)
con_mb_cxt = Maybe (GenLocated SrcSpan (HsContext GhcRn))
cxt
    , con_args :: forall pass. ConDecl pass -> HsConDeclDetails pass
con_args = HsConDeclDetails GhcRn
args, con_res_ty :: forall pass. ConDecl pass -> LHsType pass
con_res_ty = LHsType GhcRn
res_ty, con_g_ext :: forall pass. ConDecl pass -> XConDeclGADT pass
con_g_ext = XConDeclGADT GhcRn
implicit_tkv_nms })
  = -- Even though the GADT-style data constructor's type is closed,
    -- we must still kind-check the type, because that may influence
    -- the inferred kind of the /type/ constructor.  Example:
    --    data T f a where
    --      MkT :: f a -> T f a
    -- If we don't look at MkT we won't get the correct kind
    -- for the type constructor T
    SDoc -> TcRn () -> TcRn ()
forall a. SDoc -> TcM a -> TcM a
addErrCtxt ([Located Name] -> SDoc
dataConCtxtName [Located Name]
[GenLocated SrcSpan (IdP GhcRn)]
names) (TcRn () -> TcRn ()) -> TcRn () -> TcRn ()
forall a b. (a -> b) -> a -> b
$
    TcM ([TyVar], ([VarBndr TyVar Specificity], ())) -> TcRn ()
forall a. TcM a -> TcRn ()
discardResult (TcM ([TyVar], ([VarBndr TyVar Specificity], ())) -> TcRn ())
-> TcM ([TyVar], ([VarBndr TyVar Specificity], ())) -> TcRn ()
forall a b. (a -> b) -> a -> b
$
    [Name]
-> TcM ([VarBndr TyVar Specificity], ())
-> TcM ([TyVar], ([VarBndr TyVar Specificity], ()))
forall a. [Name] -> TcM a -> TcM ([TyVar], a)
bindImplicitTKBndrs_Tv [Name]
XConDeclGADT GhcRn
implicit_tkv_nms (TcM ([VarBndr TyVar Specificity], ())
 -> TcM ([TyVar], ([VarBndr TyVar Specificity], ())))
-> TcM ([VarBndr TyVar Specificity], ())
-> TcM ([TyVar], ([VarBndr TyVar Specificity], ()))
forall a b. (a -> b) -> a -> b
$
    [LHsTyVarBndr Specificity GhcRn]
-> TcRn () -> TcM ([VarBndr TyVar Specificity], ())
forall flag a.
OutputableBndrFlag flag =>
[LHsTyVarBndr flag GhcRn] -> TcM a -> TcM ([VarBndr TyVar flag], a)
bindExplicitTKBndrs_Tv [LHsTyVarBndr Specificity GhcRn]
explicit_tkv_nms (TcRn () -> TcM ([VarBndr TyVar Specificity], ()))
-> TcRn () -> TcM ([VarBndr TyVar Specificity], ())
forall a b. (a -> b) -> a -> b
$
        -- Why "_Tv"?  See Note [Kind-checking for GADTs]
    do { [Type]
_ <- Maybe (GenLocated SrcSpan (HsContext GhcRn)) -> TcM [Type]
tcHsMbContext Maybe (GenLocated SrcSpan (HsContext GhcRn))
cxt
       ; NewOrData -> Type -> [HsScaled GhcRn (LHsType GhcRn)] -> TcRn ()
kcConArgTys NewOrData
new_or_data Type
res_kind (HsConDeclDetails GhcRn -> [HsScaled GhcRn (LHsType GhcRn)]
forall pass.
HsConDeclDetails pass -> [HsScaled pass (LBangType pass)]
hsConDeclArgTys HsConDeclDetails GhcRn
args)
       ; Type
_ <- LHsType GhcRn -> TcM Type
tcHsOpenType LHsType GhcRn
res_ty
       ; () -> TcRn ()
forall (m :: * -> *) a. Monad m => a -> m a
return () }

{- Note [kcConDecls result kind]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
We might have e.g.
    data T a :: Type -> Type where ...
or
    newtype instance N a :: Type -> Type  where ..
in which case, the 'res_kind' passed to kcConDecls will be
   Type->Type

We must look past those arrows, or even foralls, to the Type in the
corner, to pass to kcConDecl c.f. #16828. Hence the splitPiTys here.

I am a bit concerned about tycons with a declaration like
   data T a :: Type -> forall k. k -> Type  where ...

It does not have a CUSK, so kcInferDeclHeader will make a TcTyCon
with tyConResKind of Type -> forall k. k -> Type.  Even that is fine:
the splitPiTys will look past the forall.  But I'm bothered about
what if the type "in the corner" mentions k?  This is incredibly
obscure but something like this could be bad:
   data T a :: Type -> foral k. k -> TYPE (F k) where ...

I bet we are not quite right here, but my brain suffered a buffer
overflow and I thought it best to nail the common cases right now.

Note [Recursion and promoting data constructors]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
We don't want to allow promotion in a strongly connected component
when kind checking.

Consider:
  data T f = K (f (K Any))

When kind checking the `data T' declaration the local env contains the
mappings:
  T -> ATcTyCon <some initial kind>
  K -> APromotionErr

APromotionErr is only used for DataCons, and only used during type checking
in tcTyClGroup.

Note [Kind-checking for GADTs]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Consider

  data Proxy a where
    MkProxy1 :: forall k (b :: k). Proxy b
    MkProxy2 :: forall j (c :: j). Proxy c

It seems reasonable that this should be accepted. But something very strange
is going on here: when we're kind-checking this declaration, we need to unify
the kind of `a` with k and j -- even though k and j's scopes are local to the type of
MkProxy{1,2}. The best approach we've come up with is to use TyVarTvs during
the kind-checking pass. First off, note that it's OK if the kind-checking pass
is too permissive: we'll snag the problems in the type-checking pass later.
(This extra permissiveness might happen with something like

  data SameKind :: k -> k -> Type
  data Bad a where
    MkBad :: forall k1 k2 (a :: k1) (b :: k2). Bad (SameKind a b)

which would be accepted if k1 and k2 were TyVarTvs. This is correctly rejected
in the second pass, though. Test case: polykinds/TyVarTvKinds3)
Recall that the kind-checking pass exists solely to collect constraints
on the kinds and to power unification.

To achieve the use of TyVarTvs, we must be careful to use specialized functions
that produce TyVarTvs, not ordinary skolems. This is why we need
kcExplicitTKBndrs and kcImplicitTKBndrs in GHC.Tc.Gen.HsType, separate from their
tc... variants.

The drawback of this approach is sometimes it will accept a definition that
a (hypothetical) declarative specification would likely reject. As a general
rule, we don't want to allow polymorphic recursion without a CUSK. Indeed,
the whole point of CUSKs is to allow polymorphic recursion. Yet, the TyVarTvs
approach allows a limited form of polymorphic recursion *without* a CUSK.

To wit:
  data T a = forall k (b :: k). MkT (T b) Int
  (test case: dependent/should_compile/T14066a)

Note that this is polymorphically recursive, with the recursive occurrence
of T used at a kind other than a's kind. The approach outlined here accepts
this definition, because this kind is still a kind variable (and so the
TyVarTvs unify). Stepping back, I (Richard) have a hard time envisioning a
way to describe exactly what declarations will be accepted and which will
be rejected (without a CUSK). However, the accepted definitions are indeed
well-kinded and any rejected definitions would be accepted with a CUSK,
and so this wrinkle need not cause anyone to lose sleep.

************************************************************************
*                                                                      *
\subsection{Type checking}
*                                                                      *
************************************************************************

Note [Type checking recursive type and class declarations]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
At this point we have completed *kind-checking* of a mutually
recursive group of type/class decls (done in kcTyClGroup). However,
we discarded the kind-checked types (eg RHSs of data type decls);
note that kcTyClDecl returns ().  There are two reasons:

  * It's convenient, because we don't have to rebuild a
    kinded HsDecl (a fairly elaborate type)

  * It's necessary, because after kind-generalisation, the
    TyCons/Classes may now be kind-polymorphic, and hence need
    to be given kind arguments.

Example:
       data T f a = MkT (f a) (T f a)
During kind-checking, we give T the kind T :: k1 -> k2 -> *
and figure out constraints on k1, k2 etc. Then we generalise
to get   T :: forall k. (k->*) -> k -> *
So now the (T f a) in the RHS must be elaborated to (T k f a).

However, during tcTyClDecl of T (above) we will be in a recursive
"knot". So we aren't allowed to look at the TyCon T itself; we are only
allowed to put it (lazily) in the returned structures.  But when
kind-checking the RHS of T's decl, we *do* need to know T's kind (so
that we can correctly elaboarate (T k f a).  How can we get T's kind
without looking at T?  Delicate answer: during tcTyClDecl, we extend

  *Global* env with T -> ATyCon (the (not yet built) final TyCon for T)
  *Local*  env with T -> ATcTyCon (TcTyCon with the polymorphic kind of T)

Then:

  * During GHC.Tc.Gen.HsType.tcTyVar we look in the *local* env, to get the
    fully-known, not knot-tied TcTyCon for T.

  * Then, in GHC.Tc.Utils.Zonk.zonkTcTypeToType (and zonkTcTyCon in particular)
    we look in the *global* env to get the TyCon.

This fancy footwork (with two bindings for T) is only necessary for the
TyCons or Classes of this recursive group.  Earlier, finished groups,
live in the global env only.

See also Note [Kind checking recursive type and class declarations]

Note [Kind checking recursive type and class declarations]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Before we can type-check the decls, we must kind check them. This
is done by establishing an "initial kind", which is a rather uninformed
guess at a tycon's kind (by counting arguments, mainly) and then
using this initial kind for recursive occurrences.

The initial kind is stored in exactly the same way during
kind-checking as it is during type-checking (Note [Type checking
recursive type and class declarations]): in the *local* environment,
with ATcTyCon. But we still must store *something* in the *global*
environment. Even though we discard the result of kind-checking, we
sometimes need to produce error messages. These error messages will
want to refer to the tycons being checked, except that they don't
exist yet, and it would be Terribly Annoying to get the error messages
to refer back to HsSyn. So we create a TcTyCon and put it in the
global env. This tycon can print out its name and knows its kind, but
any other action taken on it will panic. Note that TcTyCons are *not*
knot-tied, unlike the rather valid but knot-tied ones that occur
during type-checking.

Note [Declarations for wired-in things]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
For wired-in things we simply ignore the declaration
and take the wired-in information.  That avoids complications.
e.g. the need to make the data constructor worker name for
     a constraint tuple match the wired-in one

Note [Datatype return kinds]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~
There are several poorly lit corners around datatype/newtype return kinds.
This Note explains these.  We cover data/newtype families and instances
in Note [Data family/instance return kinds].

data    T a :: <kind> where ...   -- See Point DT4
newtype T a :: <kind> where ...   -- See Point DT5

DT1 Where this applies: Only GADT syntax for data/newtype/instance declarations
    can have declared return kinds. This Note does not apply to Haskell98
    syntax.

DT2 Where these kinds come from: The return kind is part of the TyCon kind, gotten either
     by checkInitialKind (standalone kind signature / CUSK) or
     inferInitialKind. It is extracted by bindTyClTyVars in tcTyClDecl1. It is
     then passed to tcDataDefn.

DT3 Eta-expansion: Any forall-bound variables and function arguments in a result kind
    become parameters to the type. That is, when we say

     data T a :: Type -> Type where ...

    we really mean for T to have two parameters. The second parameter
    is produced by processing the return kind in etaExpandAlgTyCon,
    called in tcDataDefn.

    See also Note [TyConBinders for the result kind signatures of a data type]
    in GHC.Tc.Gen.HsType.

DT4 Datatype return kind restriction: A data type return kind must end
    in a type that, after type-synonym expansion, yields `TYPE LiftedRep`. By
    "end in", we mean we strip any foralls and function arguments off before
    checking.

    Examples:
      data T1 :: Type                          -- good
      data T2 :: Bool -> Type                  -- good
      data T3 :: Bool -> forall k. Type        -- strange, but still accepted
      data T4 :: forall k. k -> Type           -- good
      data T5 :: Bool                          -- bad
      data T6 :: Type -> Bool                  -- bad

    Exactly the same applies to data instance (but not data family)
    declarations.  Examples
      data instance D1 :: Type                 -- good
      data instance D2 :: Bool -> Type         -- good

    We can "look through" type synonyms
      type Star = Type
      data T7 :: Bool -> Star                  -- good (synonym expansion ok)
      type Arrow = (->)
      data T8 :: Arrow Bool Type               -- good (ditto)

    But we specifically do *not* do type family reduction here.
      type family ARROW where
        ARROW = (->)
      data T9 :: ARROW Bool Type               -- bad

      type family F a where
        F Int  = Bool
        F Bool = Type
      data T10 :: Bool -> F Bool               -- bad

    The /principle/ here is that in the TyCon for a data type or data instance,
    we must be able to lay out all the type-variable binders, one by one, until
    we reach (TYPE xx).  There is no place for a cast here.  We could add one,
    but let's not!

    This check is done in checkDataKindSig. For data declarations, this
    call is in tcDataDefn; for data instances, this call is in tcDataFamInstDecl.

DT5 Newtype return kind restriction.
    If -XUnliftedNewtypes is not on, then newtypes are treated just
    like datatypes --- see (4) above.

    If -XUnliftedNewtypes is on, then a newtype return kind must end in
    TYPE xyz, for some xyz (after type synonym expansion). The "xyz"
    may include type families, but the TYPE part must be visible
    /without/ expanding type families (only synonyms).

    This kind is unified with the kind of the representation type (the
    type of the one argument to the one constructor). See also steps
    (2) and (3) of Note [Implementation of UnliftedNewtypes].

    The checks are done in the same places as for datatypes.
    Examples (assume -XUnliftedNewtypes):

      newtype N1 :: Type                       -- good
      newtype N2 :: Bool -> Type               -- good
      newtype N3 :: forall r. Bool -> TYPE r   -- good

      type family F (t :: Type) :: RuntimeRep
      newtype N4 :: forall t -> TYPE (F t)     -- good

      type family STAR where
        STAR = Type
      newtype N5 :: Bool -> STAR               -- bad

Note [Data family/instance return kinds]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Within this note, understand "instance" to mean data or newtype
instance, and understand "family" to mean data family. No type
families or classes here. Some examples:

data family T a :: <kind>          -- See Point DF56

data    instance T [a] :: <kind> where ...   -- See Point DF2
newtype instance T [a] :: <kind> where ...   -- See Point DF2

Here is the Plan for Data Families:

DF0 Where these kinds come from:

    Families: The return kind is either written in a standalone signature
     or extracted from a family declaration in getInitialKind.
     If a family declaration is missing a result kind, it is assumed to be
     Type. This assumption is in getInitialKind for CUSKs or
     get_fam_decl_initial_kind for non-signature & non-CUSK cases.

   Instances: The data family already has a known kind. The return kind
     of an instance is then calculated by applying the data family tycon
     to the patterns provided, as computed by the typeKind lhs_ty in the
     end of tcDataFamInstHeader. In the case of an instance written in GADT
     syntax, there are potentially *two* return kinds: the one computed from
     applying the data family tycon to the patterns, and the one given by
     the user. This second kind is checked by the tc_kind_sig function within
     tcDataFamInstHeader. See also DF3, below.

DF1 In a data/newtype instance, we treat the kind of the /data family/,
    once instantiated, as the "master kind" for the representation
    TyCon.  For example:
        data family T1 :: Type -> Type -> Type
        data instance T1 Int :: F Bool -> Type where ...
    The "master kind" for the representation TyCon R:T1Int comes
    from T1, not from the signature on the data instance.  It is as
    if we declared
        data R:T1Int :: Type -> Type where ...
     See Note [Liberalising data family return kinds] for an alternative
     plan.  But this current plan is simple, and ensures that all instances
     are simple instantiations of the master, without strange casts.

     An example with non-trivial instantiation:
        data family T2 :: forall k. Type -> k
        data instance T2 :: Type -> Type -> Type where ...
     Here 'k' gets instantiated with (Type -> Type), driven by
     the signature on the 'data instance'. (See also DT3 of
     Note [Datatype return kinds] about eta-expansion, which applies here,
     too; see tcDataFamInstDecl's call of etaExpandAlgTyCon.)

     A newtype example:

       data Color = Red | Blue
       type family Interpret (x :: Color) :: RuntimeRep where
         Interpret 'Red = 'IntRep
         Interpret 'Blue = 'WordRep
       data family Foo (x :: Color) :: TYPE (Interpret x)
       newtype instance Foo 'Red :: TYPE IntRep where
         FooRedC :: Int# -> Foo 'Red

    Here we get that Foo 'Red :: TYPE (Interpret Red), and our
    representation newtype looks like
         newtype R:FooRed :: TYPE (Interpret Red) where
            FooRedC :: Int# -> R:FooRed
    Remember: the master kind comes from the /family/ tycon.

DF2 /After/ this instantiation, the return kind of the master kind
    must obey the usual rules for data/newtype return kinds (DT4, DT5)
    of Note [Datatype return kinds].  Examples:
        data family T3 k :: k
        data instance T3 Type where ...          -- OK
        data instance T3 (Type->Type) where ...  -- OK
        data instance T3 (F Int) where ...       -- Not OK

DF3 Any kind signatures on the data/newtype instance are checked for
    equality with the master kind (and hence may guide instantiation)
    but are otherwise ignored. So in the T1 example above, we check
    that (F Int ~ Type) by unification; but otherwise ignore the
    user-supplied signature from the /family/ not the /instance/.

    We must be sure to instantiate any trailing invisible binders
    before doing this unification.  See the call to tcInstInvisibleBinders
    in tcDataFamInstHeader. For example:
       data family D :: forall k. k
       data instance D :: Type               -- forall k. k   <:  Type
       data instance D :: Type -> Type       -- forall k. k   <:  Type -> Type
         -- NB: these do not overlap
    we must instantiate D before unifying with the signature in the
    data instance declaration

DF4 We also (redundantly) check that any user-specified return kind
    signature in the data instance also obeys DT4/DT5.  For example we
    reject
        data family T1 :: Type -> Type -> Type
        data instance T1 Int :: Type -> F Int
    even if (F Int ~ Type).  We could omit this check, because we
    use the master kind; but it seems more uniform to check it, again
    with checkDataKindSig.

DF5 Data /family/ return kind restrictions. Consider
       data family D8 a :: F a
    where F is a type family.  No data/newtype instance can instantiate
    this so that it obeys the rules of DT4 or DT5.  So GHC proactively
    rejects the data /family/ declaration if it can never satisfy (DT4)/(DT5).
    Remember that a data family supports both data and newtype instances.

    More precisely, the return kind of a data family must be either
        * TYPE xyz (for some type xyz) or
        * a kind variable
    Only in these cases can a data/newtype instance possibly satisfy (DT4)/(DT5).
    This is checked by the call to checkDataKindSig in tcFamDecl1.  Examples:

      data family D1 :: Type              -- good
      data family D2 :: Bool -> Type      -- good
      data family D3 k :: k               -- good
      data family D4 :: forall k -> k     -- good
      data family D5 :: forall k. k -> k  -- good
      data family D6 :: forall r. TYPE r  -- good
      data family D7 :: Bool -> STAR      -- bad (see STAR from point 5)

DF6 Two return kinds for instances: If an instance has two return kinds,
    one from the family declaration and one from the instance declaration
    (see point DF3 above), they are unified. More accurately, we make sure
    that the kind of the applied data family is a subkind of the user-written
    kind. GHC.Tc.Gen.HsType.checkExpectedKind normally does this check for types, but
    that's overkill for our needs here. Instead, we just instantiate any
    invisible binders in the (instantiated) kind of the data family
    (called lhs_kind in tcDataFamInstHeader) with tcInstInvisibleTyBinders
    and then unify the resulting kind with the kind written by the user.
    This unification naturally produces a coercion, which we can drop, as
    the kind annotation on the instance is redundant (except perhaps for
    effects of unification).

    This all is Wrinkle (3) in Note [Implementation of UnliftedNewtypes].

Note [Liberalising data family return kinds]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Could we allow this?
   type family F a where { F Int = Type }
   data family T a :: F a
   data instance T Int where
      MkT :: T Int

In the 'data instance', T Int :: F Int, and F Int = Type, so all seems
well.  But there are lots of complications:

* The representation constructor R:TInt presumably has kind Type.
  So the axiom connecting the two would have to look like
       axTInt :: T Int ~ R:TInt |> sym axFInt
  and that doesn't match expectation in DataFamInstTyCon
  in AlgTyConFlav

* The wrapper can't have type
     $WMkT :: Int -> T Int
  because T Int has the wrong kind.  It would have to be
     $WMkT :: Int -> (T Int) |> axFInt

* The code for $WMkT would also be more complicated, needing
  two coherence coercions. Try it!

* Code for pattern matching would be complicated in an
  exactly dual way.

So yes, we could allow this, but we currently do not. That's
why we have DF2 in Note [Data family/instance return kinds].

Note [Implementation of UnliftedNewtypes]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Expected behavior of UnliftedNewtypes:

* Proposal: https://github.com/ghc-proposals/ghc-proposals/blob/master/proposals/0013-unlifted-newtypes.rst
* Discussion: https://github.com/ghc-proposals/ghc-proposals/pull/98

What follows is a high-level overview of the implementation of the
proposal.

STEP 1: Getting the initial kind, as done by inferInitialKind. We have
two sub-cases:

* With a SAK/CUSK: no change in kind-checking; the tycon is given the kind
  the user writes, whatever it may be.

* Without a SAK/CUSK: If there is no kind signature, the tycon is given
  a kind `TYPE r`, for a fresh unification variable `r`. We do this even
  when -XUnliftedNewtypes is not on; see <Error Messages>, below.

STEP 2: Kind-checking, as done by kcTyClDecl. This step is skipped for CUSKs.
The key function here is kcConDecl, which looks at an individual constructor
declaration. When we are processing a newtype (but whether or not -XUnliftedNewtypes
is enabled; see <Error Messages>, below), we generate a correct ContextKind
for the checking argument types: see getArgExpKind.

Examples of newtypes affected by STEP 2, assuming -XUnliftedNewtypes is
enabled (we use r0 to denote a unification variable):

newtype Foo rep = MkFoo (forall (a :: TYPE rep). a)
+ kcConDecl unifies (TYPE r0) with (TYPE rep), where (TYPE r0)
  is the kind that inferInitialKind invented for (Foo rep).

data Color = Red | Blue
type family Interpret (x :: Color) :: RuntimeRep where
  Interpret 'Red = 'IntRep
  Interpret 'Blue = 'WordRep
data family Foo (x :: Color) :: TYPE (Interpret x)
newtype instance Foo 'Red = FooRedC Int#
+ kcConDecl unifies TYPE (Interpret 'Red) with TYPE 'IntRep

Note that, in the GADT case, we might have a kind signature with arrows
(newtype XYZ a b :: Type -> Type where ...). We want only the final
component of the kind for checking in kcConDecl, so we call etaExpandAlgTyCon
in kcTyClDecl.

STEP 3: Type-checking (desugaring), as done by tcTyClDecl. The key function
here is tcConDecl. Once again, we must use getArgExpKind to ensure that the
representation type's kind matches that of the newtype, for two reasons:

  A. It is possible that a GADT has a CUSK. (Note that this is *not*
     possible for H98 types.) Recall that CUSK types don't go through
     kcTyClDecl, so we might not have done this kind check.
  B. We need to produce the coercion to put on the argument type
     if the kinds are different (for both H98 and GADT).

Example of (B):

type family F a where
  F Int = LiftedRep

newtype N :: TYPE (F Int) where
  MkN :: Int -> N

We really need to have the argument to MkN be (Int |> TYPE (sym axF)), where
axF :: F Int ~ LiftedRep. That way, the argument kind is the same as the
newtype kind, which is the principal correctness condition for newtypes.

Wrinkle: Consider (#17021, typecheck/should_fail/T17021)

    type family Id (x :: a) :: a where
      Id x = x

    newtype T :: TYPE (Id LiftedRep) where
      MkT :: Int -> T

  In the type of MkT, we must end with (Int |> TYPE (sym axId)) -> T,
  never Int -> (T |> TYPE axId); otherwise, the result type of the
  constructor wouldn't match the datatype. However, type-checking the
  HsType T might reasonably result in (T |> hole). We thus must ensure
  that this cast is dropped, forcing the type-checker to add one to
  the Int instead.

  Why is it always safe to drop the cast? This result type is type-checked by
  tcHsOpenType, so its kind definitely looks like TYPE r, for some r. It is
  important that even after dropping the cast, the type's kind has the form
  TYPE r. This is guaranteed by restrictions on the kinds of datatypes.
  For example, a declaration like `newtype T :: Id Type` is rejected: a
  newtype's final kind always has the form TYPE r, just as we want.

Note that this is possible in the H98 case only for a data family, because
the H98 syntax doesn't permit a kind signature on the newtype itself.

There are also some changes for dealing with families:

1. In tcFamDecl1, we suppress a tcIsLiftedTypeKind check if
   UnliftedNewtypes is on. This allows us to write things like:
     data family Foo :: TYPE 'IntRep

2. In a newtype instance (with -XUnliftedNewtypes), if the user does
   not write a kind signature, we want to allow the possibility that
   the kind is not Type, so we use newOpenTypeKind instead of liftedTypeKind.
   This is done in tcDataFamInstHeader in GHC.Tc.TyCl.Instance. Example:

       data family Bar (a :: RuntimeRep) :: TYPE a
       newtype instance Bar 'IntRep = BarIntC Int#
       newtype instance Bar 'WordRep :: TYPE 'WordRep where
         BarWordC :: Word# -> Bar 'WordRep

   The data instance corresponding to IntRep does not specify a kind signature,
   so tc_kind_sig just returns `TYPE r0` (where `r0` is a fresh metavariable).
   The data instance corresponding to WordRep does have a kind signature, so
   we use that kind signature.

3. A data family and its newtype instance may be declared with slightly
   different kinds. See point DF6 in Note [Data family/instance return kinds]

There's also a change in the renamer:

* In GHC.RenameSource.rnTyClDecl, enabling UnliftedNewtypes changes what is means
  for a newtype to have a CUSK. This is necessary since UnliftedNewtypes
  means that, for newtypes without kind signatures, we must use the field
  inside the data constructor to determine the result kind.
  See Note [Unlifted Newtypes and CUSKs] for more detail.

For completeness, it was also necessary to make coerce work on
unlifted types, resolving #13595.

<Error Messages>: It's tempting to think that the expected kind for a newtype
constructor argument when -XUnliftedNewtypes is *not* enabled should just be Type.
But this leads to difficulty in suggesting to enable UnliftedNewtypes. Here is
an example:

  newtype A = MkA Int#

If we expect the argument to MkA to have kind Type, then we get a kind-mismatch
error. The problem is that there is no way to connect this mismatch error to
-XUnliftedNewtypes, and suggest enabling the extension. So, instead, we allow
the A to type-check, but then find the problem when doing validity checking (and
where we get make a suitable error message). One potential worry is

  {-# LANGUAGE PolyKinds #-}
  newtype B a = MkB a

This turns out OK, because unconstrained RuntimeReps default to LiftedRep, just
as we would like. Another potential problem comes in a case like

  -- no UnliftedNewtypes

  data family D :: k
  newtype instance D = MkD Any

Here, we want inference to tell us that k should be instantiated to Type in
the instance. With the approach described here (checking for Type only in
the validity checker), that will not happen. But I cannot think of a non-contrived
example that will notice this lack of inference, so it seems better to improve
error messages than be able to infer this instantiation.

-}

tcTyClDecl :: RolesInfo -> LTyClDecl GhcRn -> TcM (TyCon, [DerivInfo])
tcTyClDecl :: (Name -> [Role])
-> LTyClDecl GhcRn
-> IOEnv (Env TcGblEnv TcLclEnv) (TyCon, [DerivInfo])
tcTyClDecl Name -> [Role]
roles_info (L SrcSpan
loc TyClDecl GhcRn
decl)
  | Just TyThing
thing <- Name -> Maybe TyThing
wiredInNameTyThing_maybe (TyClDecl GhcRn -> IdP GhcRn
forall (p :: Pass). TyClDecl (GhcPass p) -> IdP (GhcPass p)
tcdName TyClDecl GhcRn
decl)
  = case TyThing
thing of -- See Note [Declarations for wired-in things]
      ATyCon TyCon
tc -> (TyCon, [DerivInfo])
-> IOEnv (Env TcGblEnv TcLclEnv) (TyCon, [DerivInfo])
forall (m :: * -> *) a. Monad m => a -> m a
return (TyCon
tc, TyCon -> TyClDecl GhcRn -> [DerivInfo]
wiredInDerivInfo TyCon
tc TyClDecl GhcRn
decl)
      TyThing
_ -> String
-> SDoc -> IOEnv (Env TcGblEnv TcLclEnv) (TyCon, [DerivInfo])
forall a. HasCallStack => String -> SDoc -> a
pprPanic String
"tcTyClDecl" (TyThing -> SDoc
forall a. Outputable a => a -> SDoc
ppr TyThing
thing)

  | Bool
otherwise
  = SrcSpan
-> IOEnv (Env TcGblEnv TcLclEnv) (TyCon, [DerivInfo])
-> IOEnv (Env TcGblEnv TcLclEnv) (TyCon, [DerivInfo])
forall a. SrcSpan -> TcRn a -> TcRn a
setSrcSpan SrcSpan
loc (IOEnv (Env TcGblEnv TcLclEnv) (TyCon, [DerivInfo])
 -> IOEnv (Env TcGblEnv TcLclEnv) (TyCon, [DerivInfo]))
-> IOEnv (Env TcGblEnv TcLclEnv) (TyCon, [DerivInfo])
-> IOEnv (Env TcGblEnv TcLclEnv) (TyCon, [DerivInfo])
forall a b. (a -> b) -> a -> b
$ TyClDecl GhcRn
-> IOEnv (Env TcGblEnv TcLclEnv) (TyCon, [DerivInfo])
-> IOEnv (Env TcGblEnv TcLclEnv) (TyCon, [DerivInfo])
forall a. TyClDecl GhcRn -> TcM a -> TcM a
tcAddDeclCtxt TyClDecl GhcRn
decl (IOEnv (Env TcGblEnv TcLclEnv) (TyCon, [DerivInfo])
 -> IOEnv (Env TcGblEnv TcLclEnv) (TyCon, [DerivInfo]))
-> IOEnv (Env TcGblEnv TcLclEnv) (TyCon, [DerivInfo])
-> IOEnv (Env TcGblEnv TcLclEnv) (TyCon, [DerivInfo])
forall a b. (a -> b) -> a -> b
$
    do { String -> SDoc -> TcRn ()
traceTc String
"---- tcTyClDecl ---- {" (TyClDecl GhcRn -> SDoc
forall a. Outputable a => a -> SDoc
ppr TyClDecl GhcRn
decl)
       ; (TyCon
tc, [DerivInfo]
deriv_infos) <- Maybe Class
-> (Name -> [Role])
-> TyClDecl GhcRn
-> IOEnv (Env TcGblEnv TcLclEnv) (TyCon, [DerivInfo])
tcTyClDecl1 Maybe Class
forall a. Maybe a
Nothing Name -> [Role]
roles_info TyClDecl GhcRn
decl
       ; String -> SDoc -> TcRn ()
traceTc String
"---- tcTyClDecl end ---- }" (TyCon -> SDoc
forall a. Outputable a => a -> SDoc
ppr TyCon
tc)
       ; (TyCon, [DerivInfo])
-> IOEnv (Env TcGblEnv TcLclEnv) (TyCon, [DerivInfo])
forall (m :: * -> *) a. Monad m => a -> m a
return (TyCon
tc, [DerivInfo]
deriv_infos) }

noDerivInfos :: a -> (a, [DerivInfo])
noDerivInfos :: forall a. a -> (a, [DerivInfo])
noDerivInfos a
a = (a
a, [])

wiredInDerivInfo :: TyCon -> TyClDecl GhcRn -> [DerivInfo]
wiredInDerivInfo :: TyCon -> TyClDecl GhcRn -> [DerivInfo]
wiredInDerivInfo TyCon
tycon TyClDecl GhcRn
decl
  | DataDecl { tcdDataDefn :: forall pass. TyClDecl pass -> HsDataDefn pass
tcdDataDefn = HsDataDefn GhcRn
dataDefn } <- TyClDecl GhcRn
decl
  , HsDataDefn { dd_derivs :: forall pass. HsDataDefn pass -> HsDeriving pass
dd_derivs = HsDeriving GhcRn
derivs } <- HsDataDefn GhcRn
dataDefn
  = [ DerivInfo :: TyCon
-> [(Name, TyVar)]
-> [LHsDerivingClause GhcRn]
-> SDoc
-> DerivInfo
DerivInfo { di_rep_tc :: TyCon
di_rep_tc = TyCon
tycon
                , di_scoped_tvs :: [(Name, TyVar)]
di_scoped_tvs =
                    if TyCon -> Bool
isFunTyCon TyCon
tycon Bool -> Bool -> Bool
|| TyCon -> Bool
isPrimTyCon TyCon
tycon
                       then []  -- no tyConTyVars
                       else [TyVar] -> [(Name, TyVar)]
mkTyVarNamePairs (TyCon -> [TyVar]
tyConTyVars TyCon
tycon)
                , di_clauses :: [LHsDerivingClause GhcRn]
di_clauses = HsDeriving GhcRn -> [LHsDerivingClause GhcRn]
forall l e. GenLocated l e -> e
unLoc HsDeriving GhcRn
derivs
                , di_ctxt :: SDoc
di_ctxt = TyClDecl GhcRn -> SDoc
tcMkDeclCtxt TyClDecl GhcRn
decl } ]
wiredInDerivInfo TyCon
_ TyClDecl GhcRn
_ = []

  -- "type family" declarations
tcTyClDecl1 :: Maybe Class -> RolesInfo -> TyClDecl GhcRn -> TcM (TyCon, [DerivInfo])
tcTyClDecl1 :: Maybe Class
-> (Name -> [Role])
-> TyClDecl GhcRn
-> IOEnv (Env TcGblEnv TcLclEnv) (TyCon, [DerivInfo])
tcTyClDecl1 Maybe Class
parent Name -> [Role]
_roles_info (FamDecl { tcdFam :: forall pass. TyClDecl pass -> FamilyDecl pass
tcdFam = FamilyDecl GhcRn
fd })
  = (TyCon -> (TyCon, [DerivInfo]))
-> TcRn TyCon -> IOEnv (Env TcGblEnv TcLclEnv) (TyCon, [DerivInfo])
forall (f :: * -> *) a b. Functor f => (a -> b) -> f a -> f b
fmap TyCon -> (TyCon, [DerivInfo])
forall a. a -> (a, [DerivInfo])
noDerivInfos (TcRn TyCon -> IOEnv (Env TcGblEnv TcLclEnv) (TyCon, [DerivInfo]))
-> TcRn TyCon -> IOEnv (Env TcGblEnv TcLclEnv) (TyCon, [DerivInfo])
forall a b. (a -> b) -> a -> b
$
    Maybe Class -> FamilyDecl GhcRn -> TcRn TyCon
tcFamDecl1 Maybe Class
parent FamilyDecl GhcRn
fd

  -- "type" synonym declaration
tcTyClDecl1 Maybe Class
_parent Name -> [Role]
roles_info
            (SynDecl { tcdLName :: forall pass. TyClDecl pass -> Located (IdP pass)
tcdLName = L SrcSpan
_ IdP GhcRn
tc_name
                     , tcdRhs :: forall pass. TyClDecl pass -> LHsType pass
tcdRhs   = LHsType GhcRn
rhs })
  = ASSERT( isNothing _parent )
    (TyCon -> (TyCon, [DerivInfo]))
-> TcRn TyCon -> IOEnv (Env TcGblEnv TcLclEnv) (TyCon, [DerivInfo])
forall (f :: * -> *) a b. Functor f => (a -> b) -> f a -> f b
fmap TyCon -> (TyCon, [DerivInfo])
forall a. a -> (a, [DerivInfo])
noDerivInfos (TcRn TyCon -> IOEnv (Env TcGblEnv TcLclEnv) (TyCon, [DerivInfo]))
-> TcRn TyCon -> IOEnv (Env TcGblEnv TcLclEnv) (TyCon, [DerivInfo])
forall a b. (a -> b) -> a -> b
$
    (Name -> [Role]) -> Name -> LHsType GhcRn -> TcRn TyCon
tcTySynRhs Name -> [Role]
roles_info Name
IdP GhcRn
tc_name LHsType GhcRn
rhs

  -- "data/newtype" declaration
tcTyClDecl1 Maybe Class
_parent Name -> [Role]
roles_info
            decl :: TyClDecl GhcRn
decl@(DataDecl { tcdLName :: forall pass. TyClDecl pass -> Located (IdP pass)
tcdLName = L SrcSpan
_ IdP GhcRn
tc_name
                           , tcdDataDefn :: forall pass. TyClDecl pass -> HsDataDefn pass
tcdDataDefn = HsDataDefn GhcRn
defn })
  = ASSERT( isNothing _parent )
    SDoc
-> (Name -> [Role])
-> Name
-> HsDataDefn GhcRn
-> IOEnv (Env TcGblEnv TcLclEnv) (TyCon, [DerivInfo])
tcDataDefn (TyClDecl GhcRn -> SDoc
tcMkDeclCtxt TyClDecl GhcRn
decl) Name -> [Role]
roles_info Name
IdP GhcRn
tc_name HsDataDefn GhcRn
defn

tcTyClDecl1 Maybe Class
_parent Name -> [Role]
roles_info
            (ClassDecl { tcdLName :: forall pass. TyClDecl pass -> Located (IdP pass)
tcdLName = L SrcSpan
_ IdP GhcRn
class_name
                       , tcdCtxt :: forall pass. TyClDecl pass -> LHsContext pass
tcdCtxt = GenLocated SrcSpan (HsContext GhcRn)
hs_ctxt
                       , tcdMeths :: forall pass. TyClDecl pass -> LHsBinds pass
tcdMeths = LHsBinds GhcRn
meths
                       , tcdFDs :: forall pass. TyClDecl pass -> [LHsFunDep pass]
tcdFDs = [LHsFunDep GhcRn]
fundeps
                       , tcdSigs :: forall pass. TyClDecl pass -> [LSig pass]
tcdSigs = [LSig GhcRn]
sigs
                       , tcdATs :: forall pass. TyClDecl pass -> [LFamilyDecl pass]
tcdATs = [LFamilyDecl GhcRn]
ats
                       , tcdATDefs :: forall pass. TyClDecl pass -> [LTyFamDefltDecl pass]
tcdATDefs = [LTyFamDefltDecl GhcRn]
at_defs })
  = ASSERT( isNothing _parent )
    do { Class
clas <- (Name -> [Role])
-> Name
-> GenLocated SrcSpan (HsContext GhcRn)
-> LHsBinds GhcRn
-> [LHsFunDep GhcRn]
-> [LSig GhcRn]
-> [LFamilyDecl GhcRn]
-> [LTyFamDefltDecl GhcRn]
-> TcM Class
tcClassDecl1 Name -> [Role]
roles_info Name
IdP GhcRn
class_name GenLocated SrcSpan (HsContext GhcRn)
hs_ctxt
                              LHsBinds GhcRn
meths [LHsFunDep GhcRn]
fundeps [LSig GhcRn]
sigs [LFamilyDecl GhcRn]
ats [LTyFamDefltDecl GhcRn]
at_defs
       ; (TyCon, [DerivInfo])
-> IOEnv (Env TcGblEnv TcLclEnv) (TyCon, [DerivInfo])
forall (m :: * -> *) a. Monad m => a -> m a
return (TyCon -> (TyCon, [DerivInfo])
forall a. a -> (a, [DerivInfo])
noDerivInfos (Class -> TyCon
classTyCon Class
clas)) }


{- *********************************************************************
*                                                                      *
          Class declarations
*                                                                      *
********************************************************************* -}

tcClassDecl1 :: RolesInfo -> Name -> LHsContext GhcRn
             -> LHsBinds GhcRn -> [LHsFunDep GhcRn] -> [LSig GhcRn]
             -> [LFamilyDecl GhcRn] -> [LTyFamDefltDecl GhcRn]
             -> TcM Class
tcClassDecl1 :: (Name -> [Role])
-> Name
-> GenLocated SrcSpan (HsContext GhcRn)
-> LHsBinds GhcRn
-> [LHsFunDep GhcRn]
-> [LSig GhcRn]
-> [LFamilyDecl GhcRn]
-> [LTyFamDefltDecl GhcRn]
-> TcM Class
tcClassDecl1 Name -> [Role]
roles_info Name
class_name GenLocated SrcSpan (HsContext GhcRn)
hs_ctxt LHsBinds GhcRn
meths [LHsFunDep GhcRn]
fundeps [LSig GhcRn]
sigs [LFamilyDecl GhcRn]
ats [LTyFamDefltDecl GhcRn]
at_defs
  = (Class -> TcM Class) -> TcM Class
forall a env. (a -> IOEnv env a) -> IOEnv env a
fixM ((Class -> TcM Class) -> TcM Class)
-> (Class -> TcM Class) -> TcM Class
forall a b. (a -> b) -> a -> b
$ \ Class
clas ->
    -- We need the knot because 'clas' is passed into tcClassATs
    Name -> (TyCon -> [TyConBinder] -> Type -> TcM Class) -> TcM Class
forall a.
Name -> (TyCon -> [TyConBinder] -> Type -> TcM a) -> TcM a
bindTyClTyVars Name
class_name ((TyCon -> [TyConBinder] -> Type -> TcM Class) -> TcM Class)
-> (TyCon -> [TyConBinder] -> Type -> TcM Class) -> TcM Class
forall a b. (a -> b) -> a -> b
$ \ TyCon
_ [TyConBinder]
binders Type
res_kind ->
    do { Type -> TcRn ()
checkClassKindSig Type
res_kind
       ; String -> SDoc -> TcRn ()
traceTc String
"tcClassDecl 1" (Name -> SDoc
forall a. Outputable a => a -> SDoc
ppr Name
class_name SDoc -> SDoc -> SDoc
$$ [TyConBinder] -> SDoc
forall a. Outputable a => a -> SDoc
ppr [TyConBinder]
binders)
       ; let tycon_name :: Name
tycon_name = Name
class_name        -- We use the same name
             roles :: [Role]
roles = Name -> [Role]
roles_info Name
tycon_name  -- for TyCon and Class

       ; ([Type]
ctxt, [([TyVar], [TyVar])]
fds, [TcMethInfo]
sig_stuff, [ClassATItem]
at_stuff)
            <- TcM ([Type], [([TyVar], [TyVar])], [TcMethInfo], [ClassATItem])
-> TcM ([Type], [([TyVar], [TyVar])], [TcMethInfo], [ClassATItem])
forall r. TcM r -> TcM r
pushTcLevelM_   (TcM ([Type], [([TyVar], [TyVar])], [TcMethInfo], [ClassATItem])
 -> TcM ([Type], [([TyVar], [TyVar])], [TcMethInfo], [ClassATItem]))
-> TcM ([Type], [([TyVar], [TyVar])], [TcMethInfo], [ClassATItem])
-> TcM ([Type], [([TyVar], [TyVar])], [TcMethInfo], [ClassATItem])
forall a b. (a -> b) -> a -> b
$
               TcM ([Type], [([TyVar], [TyVar])], [TcMethInfo], [ClassATItem])
-> TcM ([Type], [([TyVar], [TyVar])], [TcMethInfo], [ClassATItem])
forall r. TcM r -> TcM r
solveEqualities (TcM ([Type], [([TyVar], [TyVar])], [TcMethInfo], [ClassATItem])
 -> TcM ([Type], [([TyVar], [TyVar])], [TcMethInfo], [ClassATItem]))
-> TcM ([Type], [([TyVar], [TyVar])], [TcMethInfo], [ClassATItem])
-> TcM ([Type], [([TyVar], [TyVar])], [TcMethInfo], [ClassATItem])
forall a b. (a -> b) -> a -> b
$
               SkolemInfo
-> [TyVar]
-> TcM ([Type], [([TyVar], [TyVar])], [TcMethInfo], [ClassATItem])
-> TcM ([Type], [([TyVar], [TyVar])], [TcMethInfo], [ClassATItem])
forall result. SkolemInfo -> [TyVar] -> TcM result -> TcM result
checkTvConstraints SkolemInfo
skol_info ([TyConBinder] -> [TyVar]
forall tv argf. [VarBndr tv argf] -> [tv]
binderVars [TyConBinder]
binders) (TcM ([Type], [([TyVar], [TyVar])], [TcMethInfo], [ClassATItem])
 -> TcM ([Type], [([TyVar], [TyVar])], [TcMethInfo], [ClassATItem]))
-> TcM ([Type], [([TyVar], [TyVar])], [TcMethInfo], [ClassATItem])
-> TcM ([Type], [([TyVar], [TyVar])], [TcMethInfo], [ClassATItem])
forall a b. (a -> b) -> a -> b
$
               -- The checkTvConstraints is needed bring into scope the
               -- skolems bound by the class decl header (#17841)
               do { [Type]
ctxt <- GenLocated SrcSpan (HsContext GhcRn) -> TcM [Type]
tcHsContext GenLocated SrcSpan (HsContext GhcRn)
hs_ctxt
                  ; [([TyVar], [TyVar])]
fds  <- (Located (FunDep (Located Name))
 -> IOEnv (Env TcGblEnv TcLclEnv) ([TyVar], [TyVar]))
-> [Located (FunDep (Located Name))]
-> IOEnv (Env TcGblEnv TcLclEnv) [([TyVar], [TyVar])]
forall (t :: * -> *) (m :: * -> *) a b.
(Traversable t, Monad m) =>
(a -> m b) -> t a -> m (t b)
mapM ((FunDep (Located Name)
 -> IOEnv (Env TcGblEnv TcLclEnv) ([TyVar], [TyVar]))
-> Located (FunDep (Located Name))
-> IOEnv (Env TcGblEnv TcLclEnv) ([TyVar], [TyVar])
forall a b. (a -> TcM b) -> Located a -> TcM b
addLocM FunDep (Located Name)
-> IOEnv (Env TcGblEnv TcLclEnv) ([TyVar], [TyVar])
forall {t :: * -> *} {t :: * -> *} {l} {l}.
(Traversable t, Traversable t) =>
(t (GenLocated l Name), t (GenLocated l Name))
-> IOEnv (Env TcGblEnv TcLclEnv) (t TyVar, t TyVar)
tc_fundep) [Located (FunDep (Located Name))]
[LHsFunDep GhcRn]
fundeps
                  ; [TcMethInfo]
sig_stuff <- Name -> [LSig GhcRn] -> LHsBinds GhcRn -> TcM [TcMethInfo]
tcClassSigs Name
class_name [LSig GhcRn]
sigs LHsBinds GhcRn
meths
                  ; [ClassATItem]
at_stuff  <- Name
-> Class
-> [LFamilyDecl GhcRn]
-> [LTyFamDefltDecl GhcRn]
-> TcM [ClassATItem]
tcClassATs Name
class_name Class
clas [LFamilyDecl GhcRn]
ats [LTyFamDefltDecl GhcRn]
at_defs
                  ; ([Type], [([TyVar], [TyVar])], [TcMethInfo], [ClassATItem])
-> TcM ([Type], [([TyVar], [TyVar])], [TcMethInfo], [ClassATItem])
forall (m :: * -> *) a. Monad m => a -> m a
return ([Type]
ctxt, [([TyVar], [TyVar])]
fds, [TcMethInfo]
sig_stuff, [ClassATItem]
at_stuff) }

       -- The solveEqualities will report errors for any
       -- unsolved equalities, so these zonks should not encounter
       -- any unfilled coercion variables unless there is such an error
       -- The zonk also squeeze out the TcTyCons, and converts
       -- Skolems to tyvars.
       ; ZonkEnv
ze        <- TcM ZonkEnv
emptyZonkEnv
       ; [Type]
ctxt      <- ZonkEnv -> [Type] -> TcM [Type]
zonkTcTypesToTypesX ZonkEnv
ze [Type]
ctxt
       ; [TcMethInfo]
sig_stuff <- (TcMethInfo -> IOEnv (Env TcGblEnv TcLclEnv) TcMethInfo)
-> [TcMethInfo] -> TcM [TcMethInfo]
forall (t :: * -> *) (m :: * -> *) a b.
(Traversable t, Monad m) =>
(a -> m b) -> t a -> m (t b)
mapM (ZonkEnv -> TcMethInfo -> IOEnv (Env TcGblEnv TcLclEnv) TcMethInfo
zonkTcMethInfoToMethInfoX ZonkEnv
ze) [TcMethInfo]
sig_stuff
         -- ToDo: do we need to zonk at_stuff?

       -- TODO: Allow us to distinguish between abstract class,
       -- and concrete class with no methods (maybe by
       -- specifying a trailing where or not

       ; ClassMinimalDef
mindef <- Name -> [LSig GhcRn] -> [TcMethInfo] -> TcM ClassMinimalDef
tcClassMinimalDef Name
class_name [LSig GhcRn]
sigs [TcMethInfo]
sig_stuff
       ; Bool
is_boot <- TcRnIf TcGblEnv TcLclEnv Bool
tcIsHsBootOrSig
       ; let body :: Maybe ([Type], [ClassATItem], [TcMethInfo], ClassMinimalDef)
body | Bool
is_boot, [Type] -> Bool
forall (t :: * -> *) a. Foldable t => t a -> Bool
null [Type]
ctxt, [ClassATItem] -> Bool
forall (t :: * -> *) a. Foldable t => t a -> Bool
null [ClassATItem]
at_stuff, [TcMethInfo] -> Bool
forall (t :: * -> *) a. Foldable t => t a -> Bool
null [TcMethInfo]
sig_stuff
                  = Maybe ([Type], [ClassATItem], [TcMethInfo], ClassMinimalDef)
forall a. Maybe a
Nothing
                  | Bool
otherwise
                  = ([Type], [ClassATItem], [TcMethInfo], ClassMinimalDef)
-> Maybe ([Type], [ClassATItem], [TcMethInfo], ClassMinimalDef)
forall a. a -> Maybe a
Just ([Type]
ctxt, [ClassATItem]
at_stuff, [TcMethInfo]
sig_stuff, ClassMinimalDef
mindef)

       ; Class
clas <- Name
-> [TyConBinder]
-> [Role]
-> [([TyVar], [TyVar])]
-> Maybe ([Type], [ClassATItem], [TcMethInfo], ClassMinimalDef)
-> TcM Class
forall m n.
Name
-> [TyConBinder]
-> [Role]
-> [([TyVar], [TyVar])]
-> Maybe ([Type], [ClassATItem], [TcMethInfo], ClassMinimalDef)
-> TcRnIf m n Class
buildClass Name
class_name [TyConBinder]
binders [Role]
roles [([TyVar], [TyVar])]
fds Maybe ([Type], [ClassATItem], [TcMethInfo], ClassMinimalDef)
body
       ; String -> SDoc -> TcRn ()
traceTc String
"tcClassDecl" ([Located (FunDep (Located Name))] -> SDoc
forall a. Outputable a => a -> SDoc
ppr [Located (FunDep (Located Name))]
[LHsFunDep GhcRn]
fundeps SDoc -> SDoc -> SDoc
$$ [TyConBinder] -> SDoc
forall a. Outputable a => a -> SDoc
ppr [TyConBinder]
binders SDoc -> SDoc -> SDoc
$$
                                [([TyVar], [TyVar])] -> SDoc
forall a. Outputable a => a -> SDoc
ppr [([TyVar], [TyVar])]
fds)
       ; Class -> TcM Class
forall (m :: * -> *) a. Monad m => a -> m a
return Class
clas }
  where
    skol_info :: SkolemInfo
skol_info = TyConFlavour -> Name -> SkolemInfo
TyConSkol TyConFlavour
ClassFlavour Name
class_name
    tc_fundep :: (t (GenLocated l Name), t (GenLocated l Name))
-> IOEnv (Env TcGblEnv TcLclEnv) (t TyVar, t TyVar)
tc_fundep (t (GenLocated l Name)
tvs1, t (GenLocated l Name)
tvs2) = do { t TyVar
tvs1' <- (GenLocated l Name -> IOEnv (Env TcGblEnv TcLclEnv) TyVar)
-> t (GenLocated l Name) -> IOEnv (Env TcGblEnv TcLclEnv) (t TyVar)
forall (t :: * -> *) (m :: * -> *) a b.
(Traversable t, Monad m) =>
(a -> m b) -> t a -> m (t b)
mapM (Name -> IOEnv (Env TcGblEnv TcLclEnv) TyVar
tcLookupTyVar (Name -> IOEnv (Env TcGblEnv TcLclEnv) TyVar)
-> (GenLocated l Name -> Name)
-> GenLocated l Name
-> IOEnv (Env TcGblEnv TcLclEnv) TyVar
forall b c a. (b -> c) -> (a -> b) -> a -> c
. GenLocated l Name -> Name
forall l e. GenLocated l e -> e
unLoc) t (GenLocated l Name)
tvs1 ;
                                ; t TyVar
tvs2' <- (GenLocated l Name -> IOEnv (Env TcGblEnv TcLclEnv) TyVar)
-> t (GenLocated l Name) -> IOEnv (Env TcGblEnv TcLclEnv) (t TyVar)
forall (t :: * -> *) (m :: * -> *) a b.
(Traversable t, Monad m) =>
(a -> m b) -> t a -> m (t b)
mapM (Name -> IOEnv (Env TcGblEnv TcLclEnv) TyVar
tcLookupTyVar (Name -> IOEnv (Env TcGblEnv TcLclEnv) TyVar)
-> (GenLocated l Name -> Name)
-> GenLocated l Name
-> IOEnv (Env TcGblEnv TcLclEnv) TyVar
forall b c a. (b -> c) -> (a -> b) -> a -> c
. GenLocated l Name -> Name
forall l e. GenLocated l e -> e
unLoc) t (GenLocated l Name)
tvs2 ;
                                ; (t TyVar, t TyVar)
-> IOEnv (Env TcGblEnv TcLclEnv) (t TyVar, t TyVar)
forall (m :: * -> *) a. Monad m => a -> m a
return (t TyVar
tvs1', t TyVar
tvs2') }


{- Note [Associated type defaults]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

The following is an example of associated type defaults:
             class C a where
               data D a

               type F a b :: *
               type F a b = [a]        -- Default

Note that we can get default definitions only for type families, not data
families.
-}

tcClassATs :: Name                    -- The class name (not knot-tied)
           -> Class                   -- The class parent of this associated type
           -> [LFamilyDecl GhcRn]     -- Associated types.
           -> [LTyFamDefltDecl GhcRn] -- Associated type defaults.
           -> TcM [ClassATItem]
tcClassATs :: Name
-> Class
-> [LFamilyDecl GhcRn]
-> [LTyFamDefltDecl GhcRn]
-> TcM [ClassATItem]
tcClassATs Name
class_name Class
cls [LFamilyDecl GhcRn]
ats [LTyFamDefltDecl GhcRn]
at_defs
  = do {  -- Complain about associated type defaults for non associated-types
         [IOEnv (Env TcGblEnv TcLclEnv) Any] -> TcRn ()
forall (t :: * -> *) (m :: * -> *) a.
(Foldable t, Monad m) =>
t (m a) -> m ()
sequence_ [ SDoc -> IOEnv (Env TcGblEnv TcLclEnv) Any
forall a. SDoc -> TcM a
failWithTc (Name -> Name -> SDoc
badATErr Name
class_name Name
n)
                   | Name
n <- (LTyFamDefltDecl GhcRn -> Name)
-> [LTyFamDefltDecl GhcRn] -> [Name]
forall a b. (a -> b) -> [a] -> [b]
map LTyFamDefltDecl GhcRn -> Name
at_def_tycon [LTyFamDefltDecl GhcRn]
at_defs
                   , Bool -> Bool
not (Name
n Name -> NameSet -> Bool
`elemNameSet` NameSet
at_names) ]
       ; (LFamilyDecl GhcRn -> IOEnv (Env TcGblEnv TcLclEnv) ClassATItem)
-> [LFamilyDecl GhcRn] -> TcM [ClassATItem]
forall (t :: * -> *) (m :: * -> *) a b.
(Traversable t, Monad m) =>
(a -> m b) -> t a -> m (t b)
mapM LFamilyDecl GhcRn -> IOEnv (Env TcGblEnv TcLclEnv) ClassATItem
tc_at [LFamilyDecl GhcRn]
ats }
  where
    at_def_tycon :: LTyFamDefltDecl GhcRn -> Name
    at_def_tycon :: LTyFamDefltDecl GhcRn -> Name
at_def_tycon = TyFamInstDecl GhcRn -> Name
forall (p :: Pass). TyFamInstDecl (GhcPass p) -> IdP (GhcPass p)
tyFamInstDeclName (TyFamInstDecl GhcRn -> Name)
-> (LTyFamDefltDecl GhcRn -> TyFamInstDecl GhcRn)
-> LTyFamDefltDecl GhcRn
-> Name
forall b c a. (b -> c) -> (a -> b) -> a -> c
. LTyFamDefltDecl GhcRn -> TyFamInstDecl GhcRn
forall l e. GenLocated l e -> e
unLoc

    at_fam_name :: LFamilyDecl GhcRn -> Name
    at_fam_name :: LFamilyDecl GhcRn -> Name
at_fam_name = FamilyDecl GhcRn -> Name
forall (p :: Pass). FamilyDecl (GhcPass p) -> IdP (GhcPass p)
familyDeclName (FamilyDecl GhcRn -> Name)
-> (LFamilyDecl GhcRn -> FamilyDecl GhcRn)
-> LFamilyDecl GhcRn
-> Name
forall b c a. (b -> c) -> (a -> b) -> a -> c
. LFamilyDecl GhcRn -> FamilyDecl GhcRn
forall l e. GenLocated l e -> e
unLoc

    at_names :: NameSet
at_names = [Name] -> NameSet
mkNameSet ((LFamilyDecl GhcRn -> Name) -> [LFamilyDecl GhcRn] -> [Name]
forall a b. (a -> b) -> [a] -> [b]
map LFamilyDecl GhcRn -> Name
at_fam_name [LFamilyDecl GhcRn]
ats)

    at_defs_map :: NameEnv [LTyFamDefltDecl GhcRn]
    -- Maps an AT in 'ats' to a list of all its default defs in 'at_defs'
    at_defs_map :: NameEnv [LTyFamDefltDecl GhcRn]
at_defs_map = (LTyFamDefltDecl GhcRn
 -> NameEnv [LTyFamDefltDecl GhcRn]
 -> NameEnv [LTyFamDefltDecl GhcRn])
-> NameEnv [LTyFamDefltDecl GhcRn]
-> [LTyFamDefltDecl GhcRn]
-> NameEnv [LTyFamDefltDecl GhcRn]
forall (t :: * -> *) a b.
Foldable t =>
(a -> b -> b) -> b -> t a -> b
foldr (\LTyFamDefltDecl GhcRn
at_def NameEnv [LTyFamDefltDecl GhcRn]
nenv -> ([LTyFamDefltDecl GhcRn]
 -> [LTyFamDefltDecl GhcRn] -> [LTyFamDefltDecl GhcRn])
-> NameEnv [LTyFamDefltDecl GhcRn]
-> Name
-> [LTyFamDefltDecl GhcRn]
-> NameEnv [LTyFamDefltDecl GhcRn]
forall a. (a -> a -> a) -> NameEnv a -> Name -> a -> NameEnv a
extendNameEnv_C [LTyFamDefltDecl GhcRn]
-> [LTyFamDefltDecl GhcRn] -> [LTyFamDefltDecl GhcRn]
forall a. [a] -> [a] -> [a]
(++) NameEnv [LTyFamDefltDecl GhcRn]
nenv
                                          (LTyFamDefltDecl GhcRn -> Name
at_def_tycon LTyFamDefltDecl GhcRn
at_def) [LTyFamDefltDecl GhcRn
at_def])
                        NameEnv [LTyFamDefltDecl GhcRn]
forall a. NameEnv a
emptyNameEnv [LTyFamDefltDecl GhcRn]
at_defs

    tc_at :: LFamilyDecl GhcRn -> IOEnv (Env TcGblEnv TcLclEnv) ClassATItem
tc_at LFamilyDecl GhcRn
at = do { TyCon
fam_tc <- (FamilyDecl GhcRn -> TcRn TyCon) -> LFamilyDecl GhcRn -> TcRn TyCon
forall a b. (a -> TcM b) -> Located a -> TcM b
addLocM (Maybe Class -> FamilyDecl GhcRn -> TcRn TyCon
tcFamDecl1 (Class -> Maybe Class
forall a. a -> Maybe a
Just Class
cls)) LFamilyDecl GhcRn
at
                  ; let at_defs :: [LTyFamDefltDecl GhcRn]
at_defs = NameEnv [LTyFamDefltDecl GhcRn]
-> Name -> Maybe [LTyFamDefltDecl GhcRn]
forall a. NameEnv a -> Name -> Maybe a
lookupNameEnv NameEnv [LTyFamDefltDecl GhcRn]
at_defs_map (LFamilyDecl GhcRn -> Name
at_fam_name LFamilyDecl GhcRn
at)
                                  Maybe [LTyFamDefltDecl GhcRn]
-> [LTyFamDefltDecl GhcRn] -> [LTyFamDefltDecl GhcRn]
forall a. Maybe a -> a -> a
`orElse` []
                  ; Maybe (Type, ATValidityInfo)
atd <- TyCon
-> [LTyFamDefltDecl GhcRn] -> TcM (Maybe (Type, ATValidityInfo))
tcDefaultAssocDecl TyCon
fam_tc [LTyFamDefltDecl GhcRn]
at_defs
                  ; ClassATItem -> IOEnv (Env TcGblEnv TcLclEnv) ClassATItem
forall (m :: * -> *) a. Monad m => a -> m a
return (TyCon -> Maybe (Type, ATValidityInfo) -> ClassATItem
ATI TyCon
fam_tc Maybe (Type, ATValidityInfo)
atd) }

-------------------------
tcDefaultAssocDecl ::
     TyCon                                       -- ^ Family TyCon (not knot-tied)
  -> [LTyFamDefltDecl GhcRn]                     -- ^ Defaults
  -> TcM (Maybe (KnotTied Type, ATValidityInfo)) -- ^ Type checked RHS
tcDefaultAssocDecl :: TyCon
-> [LTyFamDefltDecl GhcRn] -> TcM (Maybe (Type, ATValidityInfo))
tcDefaultAssocDecl TyCon
_ []
  = Maybe (Type, ATValidityInfo) -> TcM (Maybe (Type, ATValidityInfo))
forall (m :: * -> *) a. Monad m => a -> m a
return Maybe (Type, ATValidityInfo)
forall a. Maybe a
Nothing  -- No default declaration

tcDefaultAssocDecl TyCon
_ (LTyFamDefltDecl GhcRn
d1:LTyFamDefltDecl GhcRn
_:[LTyFamDefltDecl GhcRn]
_)
  = SDoc -> TcM (Maybe (Type, ATValidityInfo))
forall a. SDoc -> TcM a
failWithTc (String -> SDoc
text String
"More than one default declaration for"
                SDoc -> SDoc -> SDoc
<+> Name -> SDoc
forall a. Outputable a => a -> SDoc
ppr (TyFamInstDecl GhcRn -> IdP GhcRn
forall (p :: Pass). TyFamInstDecl (GhcPass p) -> IdP (GhcPass p)
tyFamInstDeclName (LTyFamDefltDecl GhcRn -> TyFamInstDecl GhcRn
forall l e. GenLocated l e -> e
unLoc LTyFamDefltDecl GhcRn
d1)))

tcDefaultAssocDecl TyCon
fam_tc
  [L SrcSpan
loc (TyFamInstDecl { tfid_eqn :: forall pass. TyFamInstDecl pass -> TyFamInstEqn pass
tfid_eqn =
         HsIB { hsib_ext :: forall pass thing. HsImplicitBndrs pass thing -> XHsIB pass thing
hsib_ext  = XHsIB GhcRn (FamEqn GhcRn (LHsType GhcRn))
imp_vars
              , hsib_body :: forall pass thing. HsImplicitBndrs pass thing -> thing
hsib_body = FamEqn { feqn_tycon :: forall pass rhs. FamEqn pass rhs -> Located (IdP pass)
feqn_tycon = L SrcSpan
_ IdP GhcRn
tc_name
                                   , feqn_bndrs :: forall pass rhs. FamEqn pass rhs -> Maybe [LHsTyVarBndr () pass]
feqn_bndrs = Maybe [LHsTyVarBndr () GhcRn]
mb_expl_bndrs
                                   , feqn_pats :: forall pass rhs. FamEqn pass rhs -> HsTyPats pass
feqn_pats  = HsTyPats GhcRn
hs_pats
                                   , feqn_rhs :: forall pass rhs. FamEqn pass rhs -> rhs
feqn_rhs   = LHsType GhcRn
hs_rhs_ty }}})]
  = -- See Note [Type-checking default assoc decls]
    SrcSpan
-> TcM (Maybe (Type, ATValidityInfo))
-> TcM (Maybe (Type, ATValidityInfo))
forall a. SrcSpan -> TcRn a -> TcRn a
setSrcSpan SrcSpan
loc (TcM (Maybe (Type, ATValidityInfo))
 -> TcM (Maybe (Type, ATValidityInfo)))
-> TcM (Maybe (Type, ATValidityInfo))
-> TcM (Maybe (Type, ATValidityInfo))
forall a b. (a -> b) -> a -> b
$
    SDoc
-> Name
-> TcM (Maybe (Type, ATValidityInfo))
-> TcM (Maybe (Type, ATValidityInfo))
forall a. SDoc -> Name -> TcM a -> TcM a
tcAddFamInstCtxt (String -> SDoc
text String
"default type instance") Name
IdP GhcRn
tc_name (TcM (Maybe (Type, ATValidityInfo))
 -> TcM (Maybe (Type, ATValidityInfo)))
-> TcM (Maybe (Type, ATValidityInfo))
-> TcM (Maybe (Type, ATValidityInfo))
forall a b. (a -> b) -> a -> b
$
    do { String -> SDoc -> TcRn ()
traceTc String
"tcDefaultAssocDecl 1" (Name -> SDoc
forall a. Outputable a => a -> SDoc
ppr Name
IdP GhcRn
tc_name)
       ; let fam_tc_name :: Name
fam_tc_name = TyCon -> Name
tyConName TyCon
fam_tc
             vis_arity :: Arity
vis_arity = [TyVar] -> Arity
forall (t :: * -> *) a. Foldable t => t a -> Arity
length (TyCon -> [TyVar]
tyConVisibleTyVars TyCon
fam_tc)
             vis_pats :: Arity
vis_pats  = HsTyPats GhcRn -> Arity
forall tm ty. [HsArg tm ty] -> Arity
numVisibleArgs HsTyPats GhcRn
hs_pats

       -- Kind of family check
       ; ASSERT( fam_tc_name == tc_name )
         Bool -> SDoc -> TcRn ()
checkTc (TyCon -> Bool
isTypeFamilyTyCon TyCon
fam_tc) (TyCon -> SDoc
wrongKindOfFamily TyCon
fam_tc)

       -- Arity check
       ; Bool -> SDoc -> TcRn ()
checkTc (Arity
vis_pats Arity -> Arity -> Bool
forall a. Eq a => a -> a -> Bool
== Arity
vis_arity)
                 (Arity -> SDoc
wrongNumberOfParmsErr Arity
vis_arity)

       -- Typecheck RHS
       --
       -- You might think we should pass in some AssocInstInfo, as we're looking
       -- at an associated type. But this would be wrong, because an associated
       -- type default LHS can mention *different* type variables than the
       -- enclosing class. So it's treated more as a freestanding beast.
       ; ([TyVar]
qtvs, [Type]
pats, Type
rhs_ty) <- TyCon
-> AssocInstInfo
-> [Name]
-> [LHsTyVarBndr () GhcRn]
-> HsTyPats GhcRn
-> LHsType GhcRn
-> TcM ([TyVar], [Type], Type)
tcTyFamInstEqnGuts TyCon
fam_tc AssocInstInfo
NotAssociated
                                                    [Name]
XHsIB GhcRn (FamEqn GhcRn (LHsType GhcRn))
imp_vars (Maybe [LHsTyVarBndr () GhcRn]
mb_expl_bndrs Maybe [LHsTyVarBndr () GhcRn]
-> [LHsTyVarBndr () GhcRn] -> [LHsTyVarBndr () GhcRn]
forall a. Maybe a -> a -> a
`orElse` [])
                                                    HsTyPats GhcRn
hs_pats LHsType GhcRn
hs_rhs_ty

       ; let fam_tvs :: [TyVar]
fam_tvs = TyCon -> [TyVar]
tyConTyVars TyCon
fam_tc
       ; String -> SDoc -> TcRn ()
traceTc String
"tcDefaultAssocDecl 2" ([SDoc] -> SDoc
vcat
           [ String -> SDoc
text String
"hs_pats"   SDoc -> SDoc -> SDoc
<+> HsTyPats GhcRn -> SDoc
forall a. Outputable a => a -> SDoc
ppr HsTyPats GhcRn
hs_pats
           , String -> SDoc
text String
"hs_rhs_ty" SDoc -> SDoc -> SDoc
<+> LHsType GhcRn -> SDoc
forall a. Outputable a => a -> SDoc
ppr LHsType GhcRn
hs_rhs_ty
           , String -> SDoc
text String
"fam_tvs" SDoc -> SDoc -> SDoc
<+> [TyVar] -> SDoc
forall a. Outputable a => a -> SDoc
ppr [TyVar]
fam_tvs
           , String -> SDoc
text String
"qtvs"    SDoc -> SDoc -> SDoc
<+> [TyVar] -> SDoc
forall a. Outputable a => a -> SDoc
ppr [TyVar]
qtvs
             -- NB: Do *not* print `pats` or rhs_ty here, as they can mention
             -- knot-tied TyCons. See #18648.
           ])
       ; let subst :: TCvSubst
subst = case (Type -> Maybe TyVar) -> [Type] -> Maybe [TyVar]
forall (t :: * -> *) (f :: * -> *) a b.
(Traversable t, Applicative f) =>
(a -> f b) -> t a -> f (t b)
traverse Type -> Maybe TyVar
getTyVar_maybe [Type]
pats of
                       Just [TyVar]
cpt_tvs -> [TyVar] -> [Type] -> TCvSubst
HasDebugCallStack => [TyVar] -> [Type] -> TCvSubst
zipTvSubst [TyVar]
cpt_tvs ([TyVar] -> [Type]
mkTyVarTys [TyVar]
fam_tvs)
                       Maybe [TyVar]
Nothing      -> TCvSubst
emptyTCvSubst
                       -- The Nothing case can only be reached in invalid
                       -- associated type family defaults. In such cases, we
                       -- simply create an empty substitution and let GHC fall
                       -- over later, in GHC.Tc.Validity.checkValidAssocTyFamDeflt.
                       -- See Note [Type-checking default assoc decls].
       ; Maybe (Type, ATValidityInfo) -> TcM (Maybe (Type, ATValidityInfo))
forall (f :: * -> *) a. Applicative f => a -> f a
pure (Maybe (Type, ATValidityInfo)
 -> TcM (Maybe (Type, ATValidityInfo)))
-> Maybe (Type, ATValidityInfo)
-> TcM (Maybe (Type, ATValidityInfo))
forall a b. (a -> b) -> a -> b
$ (Type, ATValidityInfo) -> Maybe (Type, ATValidityInfo)
forall a. a -> Maybe a
Just (TCvSubst -> Type -> Type
substTyUnchecked TCvSubst
subst Type
rhs_ty, SrcSpan -> [Type] -> ATValidityInfo
ATVI SrcSpan
loc [Type]
pats)
           -- We perform checks for well-formedness and validity later, in
           -- GHC.Tc.Validity.checkValidAssocTyFamDeflt.
     }

{- Note [Type-checking default assoc decls]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Consider this default declaration for an associated type

   class C a where
      type F (a :: k) b :: Type
      type F (x :: j) y = Proxy x -> y

Note that the class variable 'a' doesn't scope over the default assoc
decl, nor do the type variables `k` and `b`. Instead, the default decl is
treated more like a top-level type instance. However, we store the default rhs
(Proxy x -> y) in F's TyCon, using F's own type variables, so we need to
convert it to (Proxy a -> b). We do this in the tcDefaultAssocDecl function by
creating a substitution [j |-> k, x |-> a, b |-> y] and applying this
substitution to the RHS.

In order to create this substitution, we must first ensure that all of
the arguments in the default instance consist of distinct type variables.
Checking for this property proves surprisingly tricky. Three potential places
where GHC could check for this property include:

1. Before typechecking (in the parser or renamer)
2. During typechecking (in tcDefaultAssocDecl)
3. After typechecking (using GHC.Tc.Validity)

Currently, GHC picks option (3) and implements this check using
GHC.Tc.Validity.checkValidAssocTyFamDeflt. GHC previously used options (1) and
(2), but neither option quite worked out for reasons that we will explain
shortly.

The first thing that checkValidAssocTyFamDeflt does is check that all arguments
in an associated type family default are type variables. As a motivating
example, consider this erroneous program (inspired by #11361):

   class C a where
      type F (a :: k) b :: Type
      type F x        b = x

If you squint, you'll notice that the kind of `x` is actually Type. However,
we cannot substitute from [Type |-> k], so we reject this default. This also
explains why GHC no longer implements option (1) above, since figuring out that
`x`'s kind is Type would be much more difficult without the knowledge that the
typechecker provides.

Next, checkValidAssocTyFamDeflt checks that all arguments are distinct. Here is
another offending example, this time taken from #13971:

   class C2 (a :: j) where
      type F2 (a :: j) (b :: k)
      type F2 (x :: z) y = SameKind x y
   data SameKind :: k -> k -> Type

All of the arguments in the default equation for `F2` are type variables, so
that passes the first check. However, if we were to build this substitution,
then both `j` and `k` map to `z`! In terms of visible kind application, it's as
if we had written `type F2 @z @z x y = SameKind @z x y`, which makes it clear
that we have duplicated a use of `z` on the LHS. Therefore, `F2`'s default is
also rejected.

There is one more design consideration in play here: what error message should
checkValidAssocTyFamDeflt produce if one of its checks fails? Ideally, it would
be something like this:

  Illegal duplicate variable ‘z’ in:
    ‘type F2 @z @z x y = ...’
    The arguments to ‘F2’ must all be distinct type variables

This requires printing out the arguments to the associated type family. This
can be dangerous, however. Consider this example, adapted from #18648:

  class C3 a where
     type F3 a
     type F3 (F3 a) = a

F3's default is illegal, since its argument is not a bare type variable. But
note that when we typecheck F3's default, the F3 type constructor is knot-tied.
Therefore, if we print the type `F3 a` in an error message, GHC will diverge!
This is the reason why GHC no longer implements option (2) above and instead
waits until /after/ typechecking has finished, at which point the typechecker
knot has been worked out.

As one final point, one might worry that the typechecker knot could cause the
substitution that tcDefaultAssocDecl creates to diverge, but this is not the
case. Since the LHS of a valid associated type family default is always just
variables, it won't contain any tycons. Accordingly, the patterns used in the
substitution won't actually be knot-tied, even though we're in the knot. (This
is too delicate for my taste, but it works.) If we're dealing with /invalid/
default, such as F3's above, then we simply create an empty substitution and
rely on checkValidAssocTyFamDeflt throwing an error message afterwards before
any damage is done.
-}

{- *********************************************************************
*                                                                      *
          Type family declarations
*                                                                      *
********************************************************************* -}

tcFamDecl1 :: Maybe Class -> FamilyDecl GhcRn -> TcM TyCon
tcFamDecl1 :: Maybe Class -> FamilyDecl GhcRn -> TcRn TyCon
tcFamDecl1 Maybe Class
parent (FamilyDecl { fdInfo :: forall pass. FamilyDecl pass -> FamilyInfo pass
fdInfo = FamilyInfo GhcRn
fam_info
                              , fdLName :: forall pass. FamilyDecl pass -> Located (IdP pass)
fdLName = tc_lname :: GenLocated SrcSpan (IdP GhcRn)
tc_lname@(L SrcSpan
_ IdP GhcRn
tc_name)
                              , fdResultSig :: forall pass. FamilyDecl pass -> LFamilyResultSig pass
fdResultSig = L SrcSpan
_ FamilyResultSig GhcRn
sig
                              , fdInjectivityAnn :: forall pass. FamilyDecl pass -> Maybe (LInjectivityAnn pass)
fdInjectivityAnn = Maybe (LInjectivityAnn GhcRn)
inj })
  | FamilyInfo GhcRn
DataFamily <- FamilyInfo GhcRn
fam_info
  = Name
-> (TyCon -> [TyConBinder] -> Type -> TcRn TyCon) -> TcRn TyCon
forall a.
Name -> (TyCon -> [TyConBinder] -> Type -> TcM a) -> TcM a
bindTyClTyVars Name
IdP GhcRn
tc_name ((TyCon -> [TyConBinder] -> Type -> TcRn TyCon) -> TcRn TyCon)
-> (TyCon -> [TyConBinder] -> Type -> TcRn TyCon) -> TcRn TyCon
forall a b. (a -> b) -> a -> b
$ \ TyCon
_ [TyConBinder]
binders Type
res_kind -> do
  { String -> SDoc -> TcRn ()
traceTc String
"data family:" (Name -> SDoc
forall a. Outputable a => a -> SDoc
ppr Name
IdP GhcRn
tc_name)
  ; Name -> TcRn ()
checkFamFlag Name
IdP GhcRn
tc_name

  -- Check that the result kind is OK
  -- We allow things like
  --   data family T (a :: Type) :: forall k. k -> Type
  -- We treat T as having arity 1, but result kind forall k. k -> Type
  -- But we want to check that the result kind finishes in
  --   Type or a kind-variable
  -- For the latter, consider
  --   data family D a :: forall k. Type -> k
  -- When UnliftedNewtypes is enabled, we loosen this restriction
  -- on the return kind. See Note [Implementation of UnliftedNewtypes], wrinkle (1).
  -- See also Note [Datatype return kinds]
  ; DataSort -> Type -> TcRn ()
checkDataKindSig DataSort
DataFamilySort Type
res_kind
  ; Name
tc_rep_name <- Name -> TcRnIf TcGblEnv TcLclEnv Name
forall gbl lcl. Name -> TcRnIf gbl lcl Name
newTyConRepName Name
IdP GhcRn
tc_name
  ; let inj :: Injectivity
inj   = [Bool] -> Injectivity
Injective ([Bool] -> Injectivity) -> [Bool] -> Injectivity
forall a b. (a -> b) -> a -> b
$ Arity -> Bool -> [Bool]
forall a. Arity -> a -> [a]
replicate ([TyConBinder] -> Arity
forall (t :: * -> *) a. Foldable t => t a -> Arity
length [TyConBinder]
binders) Bool
True
        tycon :: TyCon
tycon = Name
-> [TyConBinder]
-> Type
-> Maybe Name
-> FamTyConFlav
-> Maybe Class
-> Injectivity
-> TyCon
mkFamilyTyCon Name
IdP GhcRn
tc_name [TyConBinder]
binders
                              Type
res_kind
                              (FamilyResultSig GhcRn -> Maybe (IdP GhcRn)
forall (a :: Pass).
FamilyResultSig (GhcPass a) -> Maybe (IdP (GhcPass a))
resultVariableName FamilyResultSig GhcRn
sig)
                              (Name -> FamTyConFlav
DataFamilyTyCon Name
tc_rep_name)
                              Maybe Class
parent Injectivity
inj
  ; TyCon -> TcRn TyCon
forall (m :: * -> *) a. Monad m => a -> m a
return TyCon
tycon }

  | FamilyInfo GhcRn
OpenTypeFamily <- FamilyInfo GhcRn
fam_info
  = Name
-> (TyCon -> [TyConBinder] -> Type -> TcRn TyCon) -> TcRn TyCon
forall a.
Name -> (TyCon -> [TyConBinder] -> Type -> TcM a) -> TcM a
bindTyClTyVars Name
IdP GhcRn
tc_name ((TyCon -> [TyConBinder] -> Type -> TcRn TyCon) -> TcRn TyCon)
-> (TyCon -> [TyConBinder] -> Type -> TcRn TyCon) -> TcRn TyCon
forall a b. (a -> b) -> a -> b
$ \ TyCon
_ [TyConBinder]
binders Type
res_kind -> do
  { String -> SDoc -> TcRn ()
traceTc String
"open type family:" (Name -> SDoc
forall a. Outputable a => a -> SDoc
ppr Name
IdP GhcRn
tc_name)
  ; Name -> TcRn ()
checkFamFlag Name
IdP GhcRn
tc_name
  ; Injectivity
inj' <- [TyConBinder] -> Maybe (LInjectivityAnn GhcRn) -> TcM Injectivity
tcInjectivity [TyConBinder]
binders Maybe (LInjectivityAnn GhcRn)
inj
  ; Name -> FamilyResultSig GhcRn -> TcRn ()
checkResultSigFlag Name
IdP GhcRn
tc_name FamilyResultSig GhcRn
sig  -- check after injectivity for better errors
  ; let tycon :: TyCon
tycon = Name
-> [TyConBinder]
-> Type
-> Maybe Name
-> FamTyConFlav
-> Maybe Class
-> Injectivity
-> TyCon
mkFamilyTyCon Name
IdP GhcRn
tc_name [TyConBinder]
binders Type
res_kind
                               (FamilyResultSig GhcRn -> Maybe (IdP GhcRn)
forall (a :: Pass).
FamilyResultSig (GhcPass a) -> Maybe (IdP (GhcPass a))
resultVariableName FamilyResultSig GhcRn
sig) FamTyConFlav
OpenSynFamilyTyCon
                               Maybe Class
parent Injectivity
inj'
  ; TyCon -> TcRn TyCon
forall (m :: * -> *) a. Monad m => a -> m a
return TyCon
tycon }

  | ClosedTypeFamily Maybe [LTyFamInstEqn GhcRn]
mb_eqns <- FamilyInfo GhcRn
fam_info
  = -- Closed type families are a little tricky, because they contain the definition
    -- of both the type family and the equations for a CoAxiom.
    do { String -> SDoc -> TcRn ()
traceTc String
"Closed type family:" (Name -> SDoc
forall a. Outputable a => a -> SDoc
ppr Name
IdP GhcRn
tc_name)
         -- the variables in the header scope only over the injectivity
         -- declaration but this is not involved here
       ; (Injectivity
inj', [TyConBinder]
binders, Type
res_kind)
            <- Name
-> (TyCon
    -> [TyConBinder] -> Type -> TcM (Injectivity, [TyConBinder], Type))
-> TcM (Injectivity, [TyConBinder], Type)
forall a.
Name -> (TyCon -> [TyConBinder] -> Type -> TcM a) -> TcM a
bindTyClTyVars Name
IdP GhcRn
tc_name ((TyCon
  -> [TyConBinder] -> Type -> TcM (Injectivity, [TyConBinder], Type))
 -> TcM (Injectivity, [TyConBinder], Type))
-> (TyCon
    -> [TyConBinder] -> Type -> TcM (Injectivity, [TyConBinder], Type))
-> TcM (Injectivity, [TyConBinder], Type)
forall a b. (a -> b) -> a -> b
$ \ TyCon
_ [TyConBinder]
binders Type
res_kind ->
               do { Injectivity
inj' <- [TyConBinder] -> Maybe (LInjectivityAnn GhcRn) -> TcM Injectivity
tcInjectivity [TyConBinder]
binders Maybe (LInjectivityAnn GhcRn)
inj
                  ; (Injectivity, [TyConBinder], Type)
-> TcM (Injectivity, [TyConBinder], Type)
forall (m :: * -> *) a. Monad m => a -> m a
return (Injectivity
inj', [TyConBinder]
binders, Type
res_kind) }

       ; Name -> TcRn ()
checkFamFlag Name
IdP GhcRn
tc_name -- make sure we have -XTypeFamilies
       ; Name -> FamilyResultSig GhcRn -> TcRn ()
checkResultSigFlag Name
IdP GhcRn
tc_name FamilyResultSig GhcRn
sig

         -- If Nothing, this is an abstract family in a hs-boot file;
         -- but eqns might be empty in the Just case as well
       ; case Maybe [LTyFamInstEqn GhcRn]
mb_eqns of
           Maybe [LTyFamInstEqn GhcRn]
Nothing   ->
               TyCon -> TcRn TyCon
forall (m :: * -> *) a. Monad m => a -> m a
return (TyCon -> TcRn TyCon) -> TyCon -> TcRn TyCon
forall a b. (a -> b) -> a -> b
$ Name
-> [TyConBinder]
-> Type
-> Maybe Name
-> FamTyConFlav
-> Maybe Class
-> Injectivity
-> TyCon
mkFamilyTyCon Name
IdP GhcRn
tc_name [TyConBinder]
binders Type
res_kind
                                      (FamilyResultSig GhcRn -> Maybe (IdP GhcRn)
forall (a :: Pass).
FamilyResultSig (GhcPass a) -> Maybe (IdP (GhcPass a))
resultVariableName FamilyResultSig GhcRn
sig)
                                      FamTyConFlav
AbstractClosedSynFamilyTyCon Maybe Class
parent
                                      Injectivity
inj'
           Just [LTyFamInstEqn GhcRn]
eqns -> do {

         -- Process the equations, creating CoAxBranches
       ; let tc_fam_tc :: TyCon
tc_fam_tc = Name
-> [TyConBinder]
-> Type
-> [(Name, TyVar)]
-> Bool
-> TyConFlavour
-> TyCon
mkTcTyCon Name
IdP GhcRn
tc_name [TyConBinder]
binders Type
res_kind
                                   [(Name, TyVar)]
noTcTyConScopedTyVars
                                   Bool
False {- this doesn't matter here -}
                                   TyConFlavour
ClosedTypeFamilyFlavour

       ; [KnotTied CoAxBranch]
branches <- (LTyFamInstEqn GhcRn -> TcRn (KnotTied CoAxBranch))
-> [LTyFamInstEqn GhcRn] -> TcRn [KnotTied CoAxBranch]
forall a b. (a -> TcRn b) -> [a] -> TcRn [b]
mapAndReportM (TyCon
-> AssocInstInfo
-> LTyFamInstEqn GhcRn
-> TcRn (KnotTied CoAxBranch)
tcTyFamInstEqn TyCon
tc_fam_tc AssocInstInfo
NotAssociated) [LTyFamInstEqn GhcRn]
eqns
         -- Do not attempt to drop equations dominated by earlier
         -- ones here; in the case of mutual recursion with a data
         -- type, we get a knot-tying failure.  Instead we check
         -- for this afterwards, in GHC.Tc.Validity.checkValidCoAxiom
         -- Example: tc265

         -- Create a CoAxiom, with the correct src location.
       ; Name
co_ax_name <- Located Name -> [[Type]] -> TcRnIf TcGblEnv TcLclEnv Name
newFamInstAxiomName Located Name
GenLocated SrcSpan (IdP GhcRn)
tc_lname []

       ; let mb_co_ax :: Maybe (CoAxiom Branched)
mb_co_ax
              | [LTyFamInstEqn GhcRn] -> Bool
forall (t :: * -> *) a. Foldable t => t a -> Bool
null [LTyFamInstEqn GhcRn]
eqns = Maybe (CoAxiom Branched)
forall a. Maybe a
Nothing   -- mkBranchedCoAxiom fails on empty list
              | Bool
otherwise = CoAxiom Branched -> Maybe (CoAxiom Branched)
forall a. a -> Maybe a
Just (Name -> TyCon -> [KnotTied CoAxBranch] -> CoAxiom Branched
mkBranchedCoAxiom Name
co_ax_name TyCon
fam_tc [KnotTied CoAxBranch]
branches)

             fam_tc :: TyCon
fam_tc = Name
-> [TyConBinder]
-> Type
-> Maybe Name
-> FamTyConFlav
-> Maybe Class
-> Injectivity
-> TyCon
mkFamilyTyCon Name
IdP GhcRn
tc_name [TyConBinder]
binders Type
res_kind (FamilyResultSig GhcRn -> Maybe (IdP GhcRn)
forall (a :: Pass).
FamilyResultSig (GhcPass a) -> Maybe (IdP (GhcPass a))
resultVariableName FamilyResultSig GhcRn
sig)
                      (Maybe (CoAxiom Branched) -> FamTyConFlav
ClosedSynFamilyTyCon Maybe (CoAxiom Branched)
mb_co_ax) Maybe Class
parent Injectivity
inj'

         -- We check for instance validity later, when doing validity
         -- checking for the tycon. Exception: checking equations
         -- overlap done by dropDominatedAxioms
       ; TyCon -> TcRn TyCon
forall (m :: * -> *) a. Monad m => a -> m a
return TyCon
fam_tc } }

#if __GLASGOW_HASKELL__ <= 810
  | otherwise = panic "tcFamInst1"  -- Silence pattern-exhaustiveness checker
#endif

-- | Maybe return a list of Bools that say whether a type family was declared
-- injective in the corresponding type arguments. Length of the list is equal to
-- the number of arguments (including implicit kind/coercion arguments).
-- True on position
-- N means that a function is injective in its Nth argument. False means it is
-- not.
tcInjectivity :: [TyConBinder] -> Maybe (LInjectivityAnn GhcRn)
              -> TcM Injectivity
tcInjectivity :: [TyConBinder] -> Maybe (LInjectivityAnn GhcRn) -> TcM Injectivity
tcInjectivity [TyConBinder]
_ Maybe (LInjectivityAnn GhcRn)
Nothing
  = Injectivity -> TcM Injectivity
forall (m :: * -> *) a. Monad m => a -> m a
return Injectivity
NotInjective

  -- User provided an injectivity annotation, so for each tyvar argument we
  -- check whether a type family was declared injective in that argument. We
  -- return a list of Bools, where True means that corresponding type variable
  -- was mentioned in lInjNames (type family is injective in that argument) and
  -- False means that it was not mentioned in lInjNames (type family is not
  -- injective in that type variable). We also extend injectivity information to
  -- kind variables, so if a user declares:
  --
  --   type family F (a :: k1) (b :: k2) = (r :: k3) | r -> a
  --
  -- then we mark both `a` and `k1` as injective.
  -- NB: the return kind is considered to be *input* argument to a type family.
  -- Since injectivity allows to infer input arguments from the result in theory
  -- we should always mark the result kind variable (`k3` in this example) as
  -- injective.  The reason is that result type has always an assigned kind and
  -- therefore we can always infer the result kind if we know the result type.
  -- But this does not seem to be useful in any way so we don't do it.  (Another
  -- reason is that the implementation would not be straightforward.)
tcInjectivity [TyConBinder]
tcbs (Just (L SrcSpan
loc (InjectivityAnn GenLocated SrcSpan (IdP GhcRn)
_ [GenLocated SrcSpan (IdP GhcRn)]
lInjNames)))
  = SrcSpan -> TcM Injectivity -> TcM Injectivity
forall a. SrcSpan -> TcRn a -> TcRn a
setSrcSpan SrcSpan
loc (TcM Injectivity -> TcM Injectivity)
-> TcM Injectivity -> TcM Injectivity
forall a b. (a -> b) -> a -> b
$
    do { let tvs :: [TyVar]
tvs = [TyConBinder] -> [TyVar]
forall tv argf. [VarBndr tv argf] -> [tv]
binderVars [TyConBinder]
tcbs
       ; DynFlags
dflags <- IOEnv (Env TcGblEnv TcLclEnv) DynFlags
forall (m :: * -> *). HasDynFlags m => m DynFlags
getDynFlags
       ; Bool -> SDoc -> TcRn ()
checkTc (Extension -> DynFlags -> Bool
xopt Extension
LangExt.TypeFamilyDependencies DynFlags
dflags)
                 (String -> SDoc
text String
"Illegal injectivity annotation" SDoc -> SDoc -> SDoc
$$
                  String -> SDoc
text String
"Use TypeFamilyDependencies to allow this")
       ; [TyVar]
inj_tvs <- (Located Name -> IOEnv (Env TcGblEnv TcLclEnv) TyVar)
-> [Located Name] -> TcM [TyVar]
forall (t :: * -> *) (m :: * -> *) a b.
(Traversable t, Monad m) =>
(a -> m b) -> t a -> m (t b)
mapM (Name -> IOEnv (Env TcGblEnv TcLclEnv) TyVar
tcLookupTyVar (Name -> IOEnv (Env TcGblEnv TcLclEnv) TyVar)
-> (Located Name -> Name)
-> Located Name
-> IOEnv (Env TcGblEnv TcLclEnv) TyVar
forall b c a. (b -> c) -> (a -> b) -> a -> c
. Located Name -> Name
forall l e. GenLocated l e -> e
unLoc) [Located Name]
[GenLocated SrcSpan (IdP GhcRn)]
lInjNames
       ; [TyVar]
inj_tvs <- (TyVar -> IOEnv (Env TcGblEnv TcLclEnv) TyVar)
-> [TyVar] -> TcM [TyVar]
forall (t :: * -> *) (m :: * -> *) a b.
(Traversable t, Monad m) =>
(a -> m b) -> t a -> m (t b)
mapM HasDebugCallStack => TyVar -> IOEnv (Env TcGblEnv TcLclEnv) TyVar
TyVar -> IOEnv (Env TcGblEnv TcLclEnv) TyVar
zonkTcTyVarToTyVar [TyVar]
inj_tvs -- zonk the kinds
       ; let inj_ktvs :: VarSet
inj_ktvs = (TyVar -> Bool) -> VarSet -> VarSet
filterVarSet TyVar -> Bool
isTyVar (VarSet -> VarSet) -> VarSet -> VarSet
forall a b. (a -> b) -> a -> b
$  -- no injective coercion vars
                        VarSet -> VarSet
closeOverKinds ([TyVar] -> VarSet
mkVarSet [TyVar]
inj_tvs)
       ; let inj_bools :: [Bool]
inj_bools = (TyVar -> Bool) -> [TyVar] -> [Bool]
forall a b. (a -> b) -> [a] -> [b]
map (TyVar -> VarSet -> Bool
`elemVarSet` VarSet
inj_ktvs) [TyVar]
tvs
       ; String -> SDoc -> TcRn ()
traceTc String
"tcInjectivity" ([SDoc] -> SDoc
vcat [ [TyVar] -> SDoc
forall a. Outputable a => a -> SDoc
ppr [TyVar]
tvs, [Located Name] -> SDoc
forall a. Outputable a => a -> SDoc
ppr [Located Name]
[GenLocated SrcSpan (IdP GhcRn)]
lInjNames, [TyVar] -> SDoc
forall a. Outputable a => a -> SDoc
ppr [TyVar]
inj_tvs
                                       , VarSet -> SDoc
forall a. Outputable a => a -> SDoc
ppr VarSet
inj_ktvs, [Bool] -> SDoc
forall a. Outputable a => a -> SDoc
ppr [Bool]
inj_bools ])
       ; Injectivity -> TcM Injectivity
forall (m :: * -> *) a. Monad m => a -> m a
return (Injectivity -> TcM Injectivity) -> Injectivity -> TcM Injectivity
forall a b. (a -> b) -> a -> b
$ [Bool] -> Injectivity
Injective [Bool]
inj_bools }

tcTySynRhs :: RolesInfo -> Name
           -> LHsType GhcRn -> TcM TyCon
tcTySynRhs :: (Name -> [Role]) -> Name -> LHsType GhcRn -> TcRn TyCon
tcTySynRhs Name -> [Role]
roles_info Name
tc_name LHsType GhcRn
hs_ty
  = Name
-> (TyCon -> [TyConBinder] -> Type -> TcRn TyCon) -> TcRn TyCon
forall a.
Name -> (TyCon -> [TyConBinder] -> Type -> TcM a) -> TcM a
bindTyClTyVars Name
tc_name ((TyCon -> [TyConBinder] -> Type -> TcRn TyCon) -> TcRn TyCon)
-> (TyCon -> [TyConBinder] -> Type -> TcRn TyCon) -> TcRn TyCon
forall a b. (a -> b) -> a -> b
$ \ TyCon
_ [TyConBinder]
binders Type
res_kind ->
    do { TcLclEnv
env <- TcRnIf TcGblEnv TcLclEnv TcLclEnv
forall gbl lcl. TcRnIf gbl lcl lcl
getLclEnv
       ; String -> SDoc -> TcRn ()
traceTc String
"tc-syn" (Name -> SDoc
forall a. Outputable a => a -> SDoc
ppr Name
tc_name SDoc -> SDoc -> SDoc
$$ TcTypeEnv -> SDoc
forall a. Outputable a => a -> SDoc
ppr (TcLclEnv -> TcTypeEnv
tcl_env TcLclEnv
env))
       ; Type
rhs_ty <- TcM Type -> TcM Type
forall r. TcM r -> TcM r
pushTcLevelM_   (TcM Type -> TcM Type) -> TcM Type -> TcM Type
forall a b. (a -> b) -> a -> b
$
                   TcM Type -> TcM Type
forall r. TcM r -> TcM r
solveEqualities (TcM Type -> TcM Type) -> TcM Type -> TcM Type
forall a b. (a -> b) -> a -> b
$
                   LHsType GhcRn -> ContextKind -> TcM Type
tcCheckLHsType LHsType GhcRn
hs_ty (Type -> ContextKind
TheKind Type
res_kind)
       ; Type
rhs_ty <- Type -> TcM Type
zonkTcTypeToType Type
rhs_ty
       ; let roles :: [Role]
roles = Name -> [Role]
roles_info Name
tc_name
             tycon :: TyCon
tycon = Name -> [TyConBinder] -> Type -> [Role] -> Type -> TyCon
buildSynTyCon Name
tc_name [TyConBinder]
binders Type
res_kind [Role]
roles Type
rhs_ty
       ; TyCon -> TcRn TyCon
forall (m :: * -> *) a. Monad m => a -> m a
return TyCon
tycon }

tcDataDefn :: SDoc -> RolesInfo -> Name
           -> HsDataDefn GhcRn -> TcM (TyCon, [DerivInfo])
  -- NB: not used for newtype/data instances (whether associated or not)
tcDataDefn :: SDoc
-> (Name -> [Role])
-> Name
-> HsDataDefn GhcRn
-> IOEnv (Env TcGblEnv TcLclEnv) (TyCon, [DerivInfo])
tcDataDefn SDoc
err_ctxt Name -> [Role]
roles_info Name
tc_name
           (HsDataDefn { dd_ND :: forall pass. HsDataDefn pass -> NewOrData
dd_ND = NewOrData
new_or_data, dd_cType :: forall pass. HsDataDefn pass -> Maybe (Located CType)
dd_cType = Maybe (Located CType)
cType
                       , dd_ctxt :: forall pass. HsDataDefn pass -> LHsContext pass
dd_ctxt = GenLocated SrcSpan (HsContext GhcRn)
ctxt
                       , dd_kindSig :: forall pass. HsDataDefn pass -> Maybe (LHsKind pass)
dd_kindSig = Maybe (LHsType GhcRn)
mb_ksig  -- Already in tc's kind
                                               -- via inferInitialKinds
                       , dd_cons :: forall pass. HsDataDefn pass -> [LConDecl pass]
dd_cons = [LConDecl GhcRn]
cons
                       , dd_derivs :: forall pass. HsDataDefn pass -> HsDeriving pass
dd_derivs = HsDeriving GhcRn
derivs })
  = Name
-> (TyCon
    -> [TyConBinder]
    -> Type
    -> IOEnv (Env TcGblEnv TcLclEnv) (TyCon, [DerivInfo]))
-> IOEnv (Env TcGblEnv TcLclEnv) (TyCon, [DerivInfo])
forall a.
Name -> (TyCon -> [TyConBinder] -> Type -> TcM a) -> TcM a
bindTyClTyVars Name
tc_name ((TyCon
  -> [TyConBinder]
  -> Type
  -> IOEnv (Env TcGblEnv TcLclEnv) (TyCon, [DerivInfo]))
 -> IOEnv (Env TcGblEnv TcLclEnv) (TyCon, [DerivInfo]))
-> (TyCon
    -> [TyConBinder]
    -> Type
    -> IOEnv (Env TcGblEnv TcLclEnv) (TyCon, [DerivInfo]))
-> IOEnv (Env TcGblEnv TcLclEnv) (TyCon, [DerivInfo])
forall a b. (a -> b) -> a -> b
$ \ TyCon
tctc [TyConBinder]
tycon_binders Type
res_kind ->
       -- 'tctc' is a 'TcTyCon' and has the 'tcTyConScopedTyVars' that we need
       -- unlike the finalized 'tycon' defined above which is an 'AlgTyCon'
       --
       -- The TyCon tyvars must scope over
       --    - the stupid theta (dd_ctxt)
       --    - for H98 constructors only, the ConDecl
       -- But it does no harm to bring them into scope
       -- over GADT ConDecls as well; and it's awkward not to
    do { Bool
gadt_syntax <- Name
-> NewOrData
-> GenLocated SrcSpan (HsContext GhcRn)
-> [LConDecl GhcRn]
-> TcRnIf TcGblEnv TcLclEnv Bool
dataDeclChecks Name
tc_name NewOrData
new_or_data GenLocated SrcSpan (HsContext GhcRn)
ctxt [LConDecl GhcRn]
cons
         -- see Note [Datatype return kinds]
       ; ([TyConBinder]
extra_bndrs, Type
final_res_kind) <- [TyConBinder] -> Type -> TcM ([TyConBinder], Type)
etaExpandAlgTyCon [TyConBinder]
tycon_binders Type
res_kind

       ; TcGblEnv
tcg_env <- TcRnIf TcGblEnv TcLclEnv TcGblEnv
forall gbl lcl. TcRnIf gbl lcl gbl
getGblEnv
       ; let hsc_src :: HscSource
hsc_src = TcGblEnv -> HscSource
tcg_src TcGblEnv
tcg_env
       ; Bool -> TcRn () -> TcRn ()
forall (f :: * -> *). Applicative f => Bool -> f () -> f ()
unless (HscSource -> [LConDecl GhcRn] -> Bool
forall {a}. HscSource -> [a] -> Bool
mk_permissive_kind HscSource
hsc_src [LConDecl GhcRn]
cons) (TcRn () -> TcRn ()) -> TcRn () -> TcRn ()
forall a b. (a -> b) -> a -> b
$
         DataSort -> Type -> TcRn ()
checkDataKindSig (NewOrData -> DataSort
DataDeclSort NewOrData
new_or_data) Type
final_res_kind

       ; [Type]
stupid_tc_theta <- TcM [Type] -> TcM [Type]
forall r. TcM r -> TcM r
pushTcLevelM_ (TcM [Type] -> TcM [Type]) -> TcM [Type] -> TcM [Type]
forall a b. (a -> b) -> a -> b
$ TcM [Type] -> TcM [Type]
forall r. TcM r -> TcM r
solveEqualities (TcM [Type] -> TcM [Type]) -> TcM [Type] -> TcM [Type]
forall a b. (a -> b) -> a -> b
$ GenLocated SrcSpan (HsContext GhcRn) -> TcM [Type]
tcHsContext GenLocated SrcSpan (HsContext GhcRn)
ctxt
       ; [Type]
stupid_theta    <- [Type] -> TcM [Type]
zonkTcTypesToTypes [Type]
stupid_tc_theta
       ; Bool
kind_signatures <- Extension -> TcRnIf TcGblEnv TcLclEnv Bool
forall gbl lcl. Extension -> TcRnIf gbl lcl Bool
xoptM Extension
LangExt.KindSignatures

             -- Check that we don't use kind signatures without Glasgow extensions
       ; Bool -> TcRn () -> TcRn ()
forall (f :: * -> *). Applicative f => Bool -> f () -> f ()
when (Maybe (LHsType GhcRn) -> Bool
forall a. Maybe a -> Bool
isJust Maybe (LHsType GhcRn)
mb_ksig) (TcRn () -> TcRn ()) -> TcRn () -> TcRn ()
forall a b. (a -> b) -> a -> b
$
         Bool -> SDoc -> TcRn ()
checkTc (Bool
kind_signatures) (Name -> SDoc
badSigTyDecl Name
tc_name)

       ; TyCon
tycon <- (TyCon -> TcRn TyCon) -> TcRn TyCon
forall a env. (a -> IOEnv env a) -> IOEnv env a
fixM ((TyCon -> TcRn TyCon) -> TcRn TyCon)
-> (TyCon -> TcRn TyCon) -> TcRn TyCon
forall a b. (a -> b) -> a -> b
$ \ TyCon
tycon -> do
             { let final_bndrs :: [TyConBinder]
final_bndrs = [TyConBinder]
tycon_binders [TyConBinder] -> [TyConBinder] -> [TyConBinder]
forall a. [a] -> [a] -> [a]
`chkAppend` [TyConBinder]
extra_bndrs
                   res_ty :: Type
res_ty      = TyCon -> [Type] -> Type
mkTyConApp TyCon
tycon ([TyVar] -> [Type]
mkTyVarTys ([TyConBinder] -> [TyVar]
forall tv argf. [VarBndr tv argf] -> [tv]
binderVars [TyConBinder]
final_bndrs))
                   roles :: [Role]
roles       = Name -> [Role]
roles_info Name
tc_name
             ; [DataCon]
data_cons <- TyCon
-> NewOrData
-> [TyConBinder]
-> Type
-> Type
-> [LConDecl GhcRn]
-> TcM [DataCon]
tcConDecls
                              TyCon
tycon
                              NewOrData
new_or_data
                              [TyConBinder]
final_bndrs
                              Type
final_res_kind
                              Type
res_ty
                              [LConDecl GhcRn]
cons
             ; AlgTyConRhs
tc_rhs    <- HscSource
-> TyCon -> [DataCon] -> IOEnv (Env TcGblEnv TcLclEnv) AlgTyConRhs
mk_tc_rhs HscSource
hsc_src TyCon
tycon [DataCon]
data_cons
             ; Name
tc_rep_nm <- Name -> TcRnIf TcGblEnv TcLclEnv Name
forall gbl lcl. Name -> TcRnIf gbl lcl Name
newTyConRepName Name
tc_name
             ; TyCon -> TcRn TyCon
forall (m :: * -> *) a. Monad m => a -> m a
return (Name
-> [TyConBinder]
-> Type
-> [Role]
-> Maybe CType
-> [Type]
-> AlgTyConRhs
-> AlgTyConFlav
-> Bool
-> TyCon
mkAlgTyCon Name
tc_name
                                  [TyConBinder]
final_bndrs
                                  Type
final_res_kind
                                  [Role]
roles
                                  ((Located CType -> CType) -> Maybe (Located CType) -> Maybe CType
forall (f :: * -> *) a b. Functor f => (a -> b) -> f a -> f b
fmap Located CType -> CType
forall l e. GenLocated l e -> e
unLoc Maybe (Located CType)
cType)
                                  [Type]
stupid_theta AlgTyConRhs
tc_rhs
                                  (Name -> AlgTyConFlav
VanillaAlgTyCon Name
tc_rep_nm)
                                  Bool
gadt_syntax) }
       ; let deriv_info :: DerivInfo
deriv_info = DerivInfo :: TyCon
-> [(Name, TyVar)]
-> [LHsDerivingClause GhcRn]
-> SDoc
-> DerivInfo
DerivInfo { di_rep_tc :: TyCon
di_rep_tc = TyCon
tycon
                                    , di_scoped_tvs :: [(Name, TyVar)]
di_scoped_tvs = TyCon -> [(Name, TyVar)]
tcTyConScopedTyVars TyCon
tctc
                                    , di_clauses :: [LHsDerivingClause GhcRn]
di_clauses = HsDeriving GhcRn -> [LHsDerivingClause GhcRn]
forall l e. GenLocated l e -> e
unLoc HsDeriving GhcRn
derivs
                                    , di_ctxt :: SDoc
di_ctxt = SDoc
err_ctxt }
       ; String -> SDoc -> TcRn ()
traceTc String
"tcDataDefn" (Name -> SDoc
forall a. Outputable a => a -> SDoc
ppr Name
tc_name SDoc -> SDoc -> SDoc
$$ [TyConBinder] -> SDoc
forall a. Outputable a => a -> SDoc
ppr [TyConBinder]
tycon_binders SDoc -> SDoc -> SDoc
$$ [TyConBinder] -> SDoc
forall a. Outputable a => a -> SDoc
ppr [TyConBinder]
extra_bndrs)
       ; (TyCon, [DerivInfo])
-> IOEnv (Env TcGblEnv TcLclEnv) (TyCon, [DerivInfo])
forall (m :: * -> *) a. Monad m => a -> m a
return (TyCon
tycon, [DerivInfo
deriv_info]) }
  where
    -- Abstract data types in hsig files can have arbitrary kinds,
    -- because they may be implemented by type synonyms
    -- (which themselves can have arbitrary kinds, not just *). See #13955.
    --
    -- Note that this is only a property that data type declarations possess,
    -- so one could not have, say, a data family instance in an hsig file that
    -- has kind `Bool`. Therefore, this check need only occur in the code that
    -- typechecks data type declarations.
    mk_permissive_kind :: HscSource -> [a] -> Bool
mk_permissive_kind HscSource
HsigFile [] = Bool
True
    mk_permissive_kind HscSource
_ [a]
_ = Bool
False

    -- In hs-boot, a 'data' declaration with no constructors
    -- indicates a nominally distinct abstract data type.
    mk_tc_rhs :: HscSource
-> TyCon -> [DataCon] -> IOEnv (Env TcGblEnv TcLclEnv) AlgTyConRhs
mk_tc_rhs HscSource
HsBootFile TyCon
_ []
      = AlgTyConRhs -> IOEnv (Env TcGblEnv TcLclEnv) AlgTyConRhs
forall (m :: * -> *) a. Monad m => a -> m a
return AlgTyConRhs
AbstractTyCon

    mk_tc_rhs HscSource
HsigFile TyCon
_ [] -- ditto
      = AlgTyConRhs -> IOEnv (Env TcGblEnv TcLclEnv) AlgTyConRhs
forall (m :: * -> *) a. Monad m => a -> m a
return AlgTyConRhs
AbstractTyCon

    mk_tc_rhs HscSource
_ TyCon
tycon [DataCon]
data_cons
      = case NewOrData
new_or_data of
          NewOrData
DataType -> AlgTyConRhs -> IOEnv (Env TcGblEnv TcLclEnv) AlgTyConRhs
forall (m :: * -> *) a. Monad m => a -> m a
return ([DataCon] -> AlgTyConRhs
mkDataTyConRhs [DataCon]
data_cons)
          NewOrData
NewType  -> ASSERT( not (null data_cons) )
                      Name
-> TyCon -> DataCon -> IOEnv (Env TcGblEnv TcLclEnv) AlgTyConRhs
forall m n. Name -> TyCon -> DataCon -> TcRnIf m n AlgTyConRhs
mkNewTyConRhs Name
tc_name TyCon
tycon ([DataCon] -> DataCon
forall a. [a] -> a
head [DataCon]
data_cons)


-------------------------
kcTyFamInstEqn :: TcTyCon -> LTyFamInstEqn GhcRn -> TcM ()
-- Used for the equations of a closed type family only
-- Not used for data/type instances
kcTyFamInstEqn :: TyCon -> LTyFamInstEqn GhcRn -> TcRn ()
kcTyFamInstEqn TyCon
tc_fam_tc
    (L SrcSpan
loc (HsIB { hsib_ext :: forall pass thing. HsImplicitBndrs pass thing -> XHsIB pass thing
hsib_ext = XHsIB GhcRn (FamEqn GhcRn (LHsType GhcRn))
imp_vars
                 , hsib_body :: forall pass thing. HsImplicitBndrs pass thing -> thing
hsib_body = FamEqn { feqn_tycon :: forall pass rhs. FamEqn pass rhs -> Located (IdP pass)
feqn_tycon = L SrcSpan
_ IdP GhcRn
eqn_tc_name
                                      , feqn_bndrs :: forall pass rhs. FamEqn pass rhs -> Maybe [LHsTyVarBndr () pass]
feqn_bndrs = Maybe [LHsTyVarBndr () GhcRn]
mb_expl_bndrs
                                      , feqn_pats :: forall pass rhs. FamEqn pass rhs -> HsTyPats pass
feqn_pats  = HsTyPats GhcRn
hs_pats
                                      , feqn_rhs :: forall pass rhs. FamEqn pass rhs -> rhs
feqn_rhs   = LHsType GhcRn
hs_rhs_ty }}))
  = SrcSpan -> TcRn () -> TcRn ()
forall a. SrcSpan -> TcRn a -> TcRn a
setSrcSpan SrcSpan
loc (TcRn () -> TcRn ()) -> TcRn () -> TcRn ()
forall a b. (a -> b) -> a -> b
$
    do { String -> SDoc -> TcRn ()
traceTc String
"kcTyFamInstEqn" ([SDoc] -> SDoc
vcat
           [ String -> SDoc
text String
"tc_name ="    SDoc -> SDoc -> SDoc
<+> Name -> SDoc
forall a. Outputable a => a -> SDoc
ppr Name
IdP GhcRn
eqn_tc_name
           , String -> SDoc
text String
"fam_tc ="     SDoc -> SDoc -> SDoc
<+> TyCon -> SDoc
forall a. Outputable a => a -> SDoc
ppr TyCon
tc_fam_tc SDoc -> SDoc -> SDoc
<+> SDoc
dcolon SDoc -> SDoc -> SDoc
<+> Type -> SDoc
forall a. Outputable a => a -> SDoc
ppr (TyCon -> Type
tyConKind TyCon
tc_fam_tc)
           , String -> SDoc
text String
"hsib_vars ="  SDoc -> SDoc -> SDoc
<+> [Name] -> SDoc
forall a. Outputable a => a -> SDoc
ppr [Name]
XHsIB GhcRn (FamEqn GhcRn (LHsType GhcRn))
imp_vars
           , String -> SDoc
text String
"feqn_bndrs =" SDoc -> SDoc -> SDoc
<+> Maybe [LHsTyVarBndr () GhcRn] -> SDoc
forall a. Outputable a => a -> SDoc
ppr Maybe [LHsTyVarBndr () GhcRn]
mb_expl_bndrs
           , String -> SDoc
text String
"feqn_pats ="  SDoc -> SDoc -> SDoc
<+> HsTyPats GhcRn -> SDoc
forall a. Outputable a => a -> SDoc
ppr HsTyPats GhcRn
hs_pats ])
          -- this check reports an arity error instead of a kind error; easier for user
       ; let vis_pats :: Arity
vis_pats = HsTyPats GhcRn -> Arity
forall tm ty. [HsArg tm ty] -> Arity
numVisibleArgs HsTyPats GhcRn
hs_pats

       -- First, check if we're dealing with a closed type family equation, and
       -- if so, ensure that each equation's type constructor is for the right
       -- type family.  E.g. barf on
       --    type family F a where { G Int = Bool }
       ; Bool -> SDoc -> TcRn ()
checkTc (Name
tc_fam_tc_name Name -> Name -> Bool
forall a. Eq a => a -> a -> Bool
== Name
IdP GhcRn
eqn_tc_name) (SDoc -> TcRn ()) -> SDoc -> TcRn ()
forall a b. (a -> b) -> a -> b
$
         Name -> Name -> SDoc
wrongTyFamName Name
tc_fam_tc_name Name
IdP GhcRn
eqn_tc_name

       ; Bool -> SDoc -> TcRn ()
checkTc (Arity
vis_pats Arity -> Arity -> Bool
forall a. Eq a => a -> a -> Bool
== Arity
vis_arity) (SDoc -> TcRn ()) -> SDoc -> TcRn ()
forall a b. (a -> b) -> a -> b
$
                  Arity -> SDoc
wrongNumberOfParmsErr Arity
vis_arity

       ; TcM ([TyVar], ([TyVar], Type)) -> TcRn ()
forall a. TcM a -> TcRn ()
discardResult (TcM ([TyVar], ([TyVar], Type)) -> TcRn ())
-> TcM ([TyVar], ([TyVar], Type)) -> TcRn ()
forall a b. (a -> b) -> a -> b
$
         [Name] -> TcM ([TyVar], Type) -> TcM ([TyVar], ([TyVar], Type))
forall a. [Name] -> TcM a -> TcM ([TyVar], a)
bindImplicitTKBndrs_Q_Tv [Name]
XHsIB GhcRn (FamEqn GhcRn (LHsType GhcRn))
imp_vars (TcM ([TyVar], Type) -> TcM ([TyVar], ([TyVar], Type)))
-> TcM ([TyVar], Type) -> TcM ([TyVar], ([TyVar], Type))
forall a b. (a -> b) -> a -> b
$
         ContextKind
-> [LHsTyVarBndr () GhcRn] -> TcM Type -> TcM ([TyVar], Type)
forall a.
ContextKind -> [LHsTyVarBndr () GhcRn] -> TcM a -> TcM ([TyVar], a)
bindExplicitTKBndrs_Q_Tv ContextKind
AnyKind (Maybe [LHsTyVarBndr () GhcRn]
mb_expl_bndrs Maybe [LHsTyVarBndr () GhcRn]
-> [LHsTyVarBndr () GhcRn] -> [LHsTyVarBndr () GhcRn]
forall a. Maybe a -> a -> a
`orElse` []) (TcM Type -> TcM ([TyVar], Type))
-> TcM Type -> TcM ([TyVar], Type)
forall a b. (a -> b) -> a -> b
$
         do { (Type
_fam_app, Type
res_kind) <- TyCon -> HsTyPats GhcRn -> TcM (Type, Type)
tcFamTyPats TyCon
tc_fam_tc HsTyPats GhcRn
hs_pats
            ; LHsType GhcRn -> ContextKind -> TcM Type
tcCheckLHsType LHsType GhcRn
hs_rhs_ty (Type -> ContextKind
TheKind Type
res_kind) }
             -- Why "_Tv" here?  Consider (#14066
             --  type family Bar x y where
             --      Bar (x :: a) (y :: b) = Int
             --      Bar (x :: c) (y :: d) = Bool
             -- During kind-checking, a,b,c,d should be TyVarTvs and unify appropriately
    }
  where
    vis_arity :: Arity
vis_arity = [TyVar] -> Arity
forall (t :: * -> *) a. Foldable t => t a -> Arity
length (TyCon -> [TyVar]
tyConVisibleTyVars TyCon
tc_fam_tc)
    tc_fam_tc_name :: Name
tc_fam_tc_name = TyCon -> Name
forall a. NamedThing a => a -> Name
getName TyCon
tc_fam_tc

--------------------------
tcTyFamInstEqn :: TcTyCon -> AssocInstInfo -> LTyFamInstEqn GhcRn
               -> TcM (KnotTied CoAxBranch)
-- Needs to be here, not in GHC.Tc.TyCl.Instance, because closed families
-- (typechecked here) have TyFamInstEqns

tcTyFamInstEqn :: TyCon
-> AssocInstInfo
-> LTyFamInstEqn GhcRn
-> TcRn (KnotTied CoAxBranch)
tcTyFamInstEqn TyCon
fam_tc AssocInstInfo
mb_clsinfo
    (L SrcSpan
loc (HsIB { hsib_ext :: forall pass thing. HsImplicitBndrs pass thing -> XHsIB pass thing
hsib_ext = XHsIB GhcRn (FamEqn GhcRn (LHsType GhcRn))
imp_vars
                 , hsib_body :: forall pass thing. HsImplicitBndrs pass thing -> thing
hsib_body = FamEqn { feqn_bndrs :: forall pass rhs. FamEqn pass rhs -> Maybe [LHsTyVarBndr () pass]
feqn_bndrs  = Maybe [LHsTyVarBndr () GhcRn]
mb_expl_bndrs
                                      , feqn_pats :: forall pass rhs. FamEqn pass rhs -> HsTyPats pass
feqn_pats   = HsTyPats GhcRn
hs_pats
                                      , feqn_rhs :: forall pass rhs. FamEqn pass rhs -> rhs
feqn_rhs    = LHsType GhcRn
hs_rhs_ty }}))
  = SrcSpan -> TcRn (KnotTied CoAxBranch) -> TcRn (KnotTied CoAxBranch)
forall a. SrcSpan -> TcRn a -> TcRn a
setSrcSpan SrcSpan
loc (TcRn (KnotTied CoAxBranch) -> TcRn (KnotTied CoAxBranch))
-> TcRn (KnotTied CoAxBranch) -> TcRn (KnotTied CoAxBranch)
forall a b. (a -> b) -> a -> b
$
    do { String -> SDoc -> TcRn ()
traceTc String
"tcTyFamInstEqn" (SDoc -> TcRn ()) -> SDoc -> TcRn ()
forall a b. (a -> b) -> a -> b
$
         [SDoc] -> SDoc
vcat [ TyCon -> SDoc
forall a. Outputable a => a -> SDoc
ppr TyCon
fam_tc SDoc -> SDoc -> SDoc
<+> HsTyPats GhcRn -> SDoc
forall a. Outputable a => a -> SDoc
ppr HsTyPats GhcRn
hs_pats
              , String -> SDoc
text String
"fam tc bndrs" SDoc -> SDoc -> SDoc
<+> [TyVar] -> SDoc
pprTyVars (TyCon -> [TyVar]
tyConTyVars TyCon
fam_tc)
              , case AssocInstInfo
mb_clsinfo of
                  NotAssociated {} -> SDoc
empty
                  InClsInst { ai_class :: AssocInstInfo -> Class
ai_class = Class
cls } -> String -> SDoc
text String
"class" SDoc -> SDoc -> SDoc
<+> Class -> SDoc
forall a. Outputable a => a -> SDoc
ppr Class
cls SDoc -> SDoc -> SDoc
<+> [TyVar] -> SDoc
pprTyVars (Class -> [TyVar]
classTyVars Class
cls) ]

       -- First, check the arity of visible arguments
       -- If we wait until validity checking, we'll get kind errors
       -- below when an arity error will be much easier to understand.
       -- Note that for closed type families, kcTyFamInstEqn has already
       -- checked the arity previously.
       ; let vis_arity :: Arity
vis_arity = [TyVar] -> Arity
forall (t :: * -> *) a. Foldable t => t a -> Arity
length (TyCon -> [TyVar]
tyConVisibleTyVars TyCon
fam_tc)
             vis_pats :: Arity
vis_pats  = HsTyPats GhcRn -> Arity
forall tm ty. [HsArg tm ty] -> Arity
numVisibleArgs HsTyPats GhcRn
hs_pats
       ; Bool -> SDoc -> TcRn ()
checkTc (Arity
vis_pats Arity -> Arity -> Bool
forall a. Eq a => a -> a -> Bool
== Arity
vis_arity) (SDoc -> TcRn ()) -> SDoc -> TcRn ()
forall a b. (a -> b) -> a -> b
$
         Arity -> SDoc
wrongNumberOfParmsErr Arity
vis_arity
       ; ([TyVar]
qtvs, [Type]
pats, Type
rhs_ty) <- TyCon
-> AssocInstInfo
-> [Name]
-> [LHsTyVarBndr () GhcRn]
-> HsTyPats GhcRn
-> LHsType GhcRn
-> TcM ([TyVar], [Type], Type)
tcTyFamInstEqnGuts TyCon
fam_tc AssocInstInfo
mb_clsinfo
                                      [Name]
XHsIB GhcRn (FamEqn GhcRn (LHsType GhcRn))
imp_vars (Maybe [LHsTyVarBndr () GhcRn]
mb_expl_bndrs Maybe [LHsTyVarBndr () GhcRn]
-> [LHsTyVarBndr () GhcRn] -> [LHsTyVarBndr () GhcRn]
forall a. Maybe a -> a -> a
`orElse` [])
                                      HsTyPats GhcRn
hs_pats LHsType GhcRn
hs_rhs_ty
       -- Don't print results they may be knot-tied
       -- (tcFamInstEqnGuts zonks to Type)
       ; KnotTied CoAxBranch -> TcRn (KnotTied CoAxBranch)
forall (m :: * -> *) a. Monad m => a -> m a
return ([TyVar]
-> [TyVar]
-> [TyVar]
-> [Type]
-> Type
-> [Role]
-> SrcSpan
-> KnotTied CoAxBranch
mkCoAxBranch [TyVar]
qtvs [] [] [Type]
pats Type
rhs_ty
                              ((TyVar -> Role) -> [TyVar] -> [Role]
forall a b. (a -> b) -> [a] -> [b]
map (Role -> TyVar -> Role
forall a b. a -> b -> a
const Role
Nominal) [TyVar]
qtvs)
                              SrcSpan
loc) }

{-
Kind check type patterns and kind annotate the embedded type variables.
     type instance F [a] = rhs

 * Here we check that a type instance matches its kind signature, but we do
   not check whether there is a pattern for each type index; the latter
   check is only required for type synonym instances.

Note [Instantiating a family tycon]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
It's possible that kind-checking the result of a family tycon applied to
its patterns will instantiate the tycon further. For example, we might
have

  type family F :: k where
    F = Int
    F = Maybe

After checking (F :: forall k. k) (with no visible patterns), we still need
to instantiate the k. With data family instances, this problem can be even
more intricate, due to Note [Arity of data families] in GHC.Core.FamInstEnv. See
indexed-types/should_compile/T12369 for an example.

So, the kind-checker must return the new skolems and args (that is, Type
or (Type -> Type) for the equations above) and the instantiated kind.

Note [Generalising in tcTyFamInstEqnGuts]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Suppose we have something like
  type instance forall (a::k) b. F t1 t2 = rhs

Then  imp_vars = [k], exp_bndrs = [a::k, b]

We want to quantify over
  * k, a, and b  (all user-specified)
  * and any inferred free kind vars from
      - the kinds of k, a, b
      - the types t1, t2

However, unlike a type signature like
  f :: forall (a::k). blah

we do /not/ care about the Inferred/Specified designation
or order for the final quantified tyvars.  Type-family
instances are not invoked directly in Haskell source code,
so visible type application etc plays no role.

So, the simple thing is
   - gather candidates from [k, a, b] and pats
   - quantify over them

Hence the slightly mysterious call:
    candidateQTyVarsOfTypes (pats ++ mkTyVarTys scoped_tvs)

Simple, neat, but a little non-obvious!

See also Note [Re-quantify type variables in rules] in GHC.Tc.Gen.Rule, which explains
a very similar design when generalising over the type of a rewrite rule.
-}

--------------------------
tcTyFamInstEqnGuts :: TyCon -> AssocInstInfo
                   -> [Name] -> [LHsTyVarBndr () GhcRn] -- Implicit and explicicit binder
                   -> HsTyPats GhcRn                    -- Patterns
                   -> LHsType GhcRn                     -- RHS
                   -> TcM ([TyVar], [TcType], TcType)   -- (tyvars, pats, rhs)
-- Used only for type families, not data families
tcTyFamInstEqnGuts :: TyCon
-> AssocInstInfo
-> [Name]
-> [LHsTyVarBndr () GhcRn]
-> HsTyPats GhcRn
-> LHsType GhcRn
-> TcM ([TyVar], [Type], Type)
tcTyFamInstEqnGuts TyCon
fam_tc AssocInstInfo
mb_clsinfo [Name]
imp_vars [LHsTyVarBndr () GhcRn]
exp_bndrs HsTyPats GhcRn
hs_pats LHsType GhcRn
hs_rhs_ty
  = do { String -> SDoc -> TcRn ()
traceTc String
"tcTyFamInstEqnGuts {" (TyCon -> SDoc
forall a. Outputable a => a -> SDoc
ppr TyCon
fam_tc)

       -- By now, for type families (but not data families) we should
       -- have checked that the number of patterns matches tyConArity

       -- This code is closely related to the code
       -- in GHC.Tc.Gen.HsType.kcCheckDeclHeader_cusk
       ; ([TyVar]
imp_tvs, ([TyVar]
exp_tvs, (Type
lhs_ty, Type
rhs_ty)))
               <- TcM ([TyVar], ([TyVar], (Type, Type)))
-> TcM ([TyVar], ([TyVar], (Type, Type)))
forall r. TcM r -> TcM r
pushTcLevelM_                                (TcM ([TyVar], ([TyVar], (Type, Type)))
 -> TcM ([TyVar], ([TyVar], (Type, Type))))
-> TcM ([TyVar], ([TyVar], (Type, Type)))
-> TcM ([TyVar], ([TyVar], (Type, Type)))
forall a b. (a -> b) -> a -> b
$
                  TcM ([TyVar], ([TyVar], (Type, Type)))
-> TcM ([TyVar], ([TyVar], (Type, Type)))
forall r. TcM r -> TcM r
solveEqualities                              (TcM ([TyVar], ([TyVar], (Type, Type)))
 -> TcM ([TyVar], ([TyVar], (Type, Type))))
-> TcM ([TyVar], ([TyVar], (Type, Type)))
-> TcM ([TyVar], ([TyVar], (Type, Type)))
forall a b. (a -> b) -> a -> b
$
                  [Name]
-> TcM ([TyVar], (Type, Type))
-> TcM ([TyVar], ([TyVar], (Type, Type)))
forall a. [Name] -> TcM a -> TcM ([TyVar], a)
bindImplicitTKBndrs_Q_Skol [Name]
imp_vars          (TcM ([TyVar], (Type, Type))
 -> TcM ([TyVar], ([TyVar], (Type, Type))))
-> TcM ([TyVar], (Type, Type))
-> TcM ([TyVar], ([TyVar], (Type, Type)))
forall a b. (a -> b) -> a -> b
$
                  ContextKind
-> [LHsTyVarBndr () GhcRn]
-> TcM (Type, Type)
-> TcM ([TyVar], (Type, Type))
forall a.
ContextKind -> [LHsTyVarBndr () GhcRn] -> TcM a -> TcM ([TyVar], a)
bindExplicitTKBndrs_Q_Skol ContextKind
AnyKind [LHsTyVarBndr () GhcRn]
exp_bndrs (TcM (Type, Type) -> TcM ([TyVar], (Type, Type)))
-> TcM (Type, Type) -> TcM ([TyVar], (Type, Type))
forall a b. (a -> b) -> a -> b
$
                  do { (Type
lhs_ty, Type
rhs_kind) <- TyCon -> HsTyPats GhcRn -> TcM (Type, Type)
tcFamTyPats TyCon
fam_tc HsTyPats GhcRn
hs_pats
                       -- Ensure that the instance is consistent with its
                       -- parent class (#16008)
                     ; AssocInstInfo -> Type -> TcRn ()
addConsistencyConstraints AssocInstInfo
mb_clsinfo Type
lhs_ty
                     ; Type
rhs_ty <- LHsType GhcRn -> ContextKind -> TcM Type
tcCheckLHsType LHsType GhcRn
hs_rhs_ty (Type -> ContextKind
TheKind Type
rhs_kind)
                     ; (Type, Type) -> TcM (Type, Type)
forall (m :: * -> *) a. Monad m => a -> m a
return (Type
lhs_ty, Type
rhs_ty) }

       -- See Note [Generalising in tcTyFamInstEqnGuts]
       -- This code (and the stuff immediately above) is very similar
       -- to that in tcDataFamInstHeader.  Maybe we should abstract the
       -- common code; but for the moment I concluded that it's
       -- clearer to duplicate it.  Still, if you fix a bug here,
       -- check there too!
       ; let scoped_tvs :: [TyVar]
scoped_tvs = [TyVar]
imp_tvs [TyVar] -> [TyVar] -> [TyVar]
forall a. [a] -> [a] -> [a]
++ [TyVar]
exp_tvs
       ; CandidatesQTvs
dvs  <- [Type] -> TcM CandidatesQTvs
candidateQTyVarsOfTypes (Type
lhs_ty Type -> [Type] -> [Type]
forall a. a -> [a] -> [a]
: [TyVar] -> [Type]
mkTyVarTys [TyVar]
scoped_tvs)
       ; [TyVar]
qtvs <- CandidatesQTvs -> TcM [TyVar]
quantifyTyVars CandidatesQTvs
dvs

       ; String -> SDoc -> TcRn ()
traceTc String
"tcTyFamInstEqnGuts 2" (SDoc -> TcRn ()) -> SDoc -> TcRn ()
forall a b. (a -> b) -> a -> b
$
         [SDoc] -> SDoc
vcat [ TyCon -> SDoc
forall a. Outputable a => a -> SDoc
ppr TyCon
fam_tc
              , String -> SDoc
text String
"scoped_tvs" SDoc -> SDoc -> SDoc
<+> [TyVar] -> SDoc
pprTyVars [TyVar]
scoped_tvs
              , String -> SDoc
text String
"lhs_ty"     SDoc -> SDoc -> SDoc
<+> Type -> SDoc
forall a. Outputable a => a -> SDoc
ppr Type
lhs_ty
              , String -> SDoc
text String
"dvs"        SDoc -> SDoc -> SDoc
<+> CandidatesQTvs -> SDoc
forall a. Outputable a => a -> SDoc
ppr CandidatesQTvs
dvs
              , String -> SDoc
text String
"qtvs"       SDoc -> SDoc -> SDoc
<+> [TyVar] -> SDoc
pprTyVars [TyVar]
qtvs ]

       ; (ZonkEnv
ze, [TyVar]
qtvs) <- [TyVar] -> TcM (ZonkEnv, [TyVar])
zonkTyBndrs [TyVar]
qtvs
       ; Type
lhs_ty     <- ZonkEnv -> Type -> TcM Type
zonkTcTypeToTypeX ZonkEnv
ze Type
lhs_ty
       ; Type
rhs_ty     <- ZonkEnv -> Type -> TcM Type
zonkTcTypeToTypeX ZonkEnv
ze Type
rhs_ty

       ; let pats :: [Type]
pats = Type -> [Type]
unravelFamInstPats Type
lhs_ty
             -- Note that we do this after solveEqualities
             -- so that any strange coercions inside lhs_ty
             -- have been solved before we attempt to unravel it
       ; String -> SDoc -> TcRn ()
traceTc String
"tcTyFamInstEqnGuts }" (TyCon -> SDoc
forall a. Outputable a => a -> SDoc
ppr TyCon
fam_tc SDoc -> SDoc -> SDoc
<+> [TyVar] -> SDoc
pprTyVars [TyVar]
qtvs)
       ; ([TyVar], [Type], Type) -> TcM ([TyVar], [Type], Type)
forall (m :: * -> *) a. Monad m => a -> m a
return ([TyVar]
qtvs, [Type]
pats, Type
rhs_ty) }

-----------------
unravelFamInstPats :: TcType -> [TcType]
-- Decompose fam_app to get the argument patterns
--
-- We expect fam_app to look like (F t1 .. tn)
-- tcFamTyPats is capable of returning ((F ty1 |> co) ty2),
-- but that can't happen here because we already checked the
-- arity of F matches the number of pattern
unravelFamInstPats :: Type -> [Type]
unravelFamInstPats Type
fam_app
  = case HasDebugCallStack => Type -> Maybe (TyCon, [Type])
Type -> Maybe (TyCon, [Type])
splitTyConApp_maybe Type
fam_app of
      Just (TyCon
_, [Type]
pats) -> [Type]
pats
      Maybe (TyCon, [Type])
Nothing -> String -> [Type]
forall a. String -> a
panic String
"unravelFamInstPats: Ill-typed LHS of family instance"
        -- The Nothing case cannot happen for type families, because
        -- we don't call unravelFamInstPats until we've solved the
        -- equalities. For data families, it shouldn't happen either,
        -- we need to fail hard and early if it does. See trac issue #15905
        -- for an example of this happening.

addConsistencyConstraints :: AssocInstInfo -> TcType -> TcM ()
-- In the corresponding positions of the class and type-family,
-- ensure the family argument is the same as the class argument
--   E.g    class C a b c d where
--             F c x y a :: Type
-- Here the first  arg of F should be the same as the third of C
--  and the fourth arg of F should be the same as the first of C
--
-- We emit /Derived/ constraints (a bit like fundeps) to encourage
-- unification to happen, but without actually reporting errors.
-- If, despite the efforts, corresponding positions do not match,
-- checkConsistentFamInst will complain
addConsistencyConstraints :: AssocInstInfo -> Type -> TcRn ()
addConsistencyConstraints AssocInstInfo
mb_clsinfo Type
fam_app
  | InClsInst { ai_inst_env :: AssocInstInfo -> VarEnv Type
ai_inst_env = VarEnv Type
inst_env } <- AssocInstInfo
mb_clsinfo
  , Just (TyCon
fam_tc, [Type]
pats) <- HasCallStack => Type -> Maybe (TyCon, [Type])
Type -> Maybe (TyCon, [Type])
tcSplitTyConApp_maybe Type
fam_app
  = do { let eqs :: [(Type, Type)]
eqs = [ (Type
cls_ty, Type
pat)
                   | (TyVar
fam_tc_tv, Type
pat) <- TyCon -> [TyVar]
tyConTyVars TyCon
fam_tc [TyVar] -> [Type] -> [(TyVar, Type)]
forall a b. [a] -> [b] -> [(a, b)]
`zip` [Type]
pats
                   , Just Type
cls_ty <- [VarEnv Type -> TyVar -> Maybe Type
forall a. VarEnv a -> TyVar -> Maybe a
lookupVarEnv VarEnv Type
inst_env TyVar
fam_tc_tv] ]
       ; String -> SDoc -> TcRn ()
traceTc String
"addConsistencyConstraints" ([(Type, Type)] -> SDoc
forall a. Outputable a => a -> SDoc
ppr [(Type, Type)]
eqs)
       ; CtOrigin -> [(Type, Type)] -> TcRn ()
emitDerivedEqs CtOrigin
AssocFamPatOrigin [(Type, Type)]
eqs }
    -- Improve inference
    -- Any mis-match is reports by checkConsistentFamInst
  | Bool
otherwise
  = () -> TcRn ()
forall (m :: * -> *) a. Monad m => a -> m a
return ()

{- Note [Constraints in patterns]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
NB: This isn't the whole story. See comment in tcFamTyPats.

At first glance, it seems there is a complicated story to tell in tcFamTyPats
around constraint solving. After all, type family patterns can now do
GADT pattern-matching, which is jolly complicated. But, there's a key fact
which makes this all simple: everything is at top level! There cannot
be untouchable type variables. There can't be weird interaction between
case branches. There can't be global skolems.

This means that the semantics of type-level GADT matching is a little
different than term level. If we have

  data G a where
    MkGBool :: G Bool

And then

  type family F (a :: G k) :: k
  type instance F MkGBool = True

we get

  axF : F Bool (MkGBool <Bool>) ~ True

Simple! No casting on the RHS, because we can affect the kind parameter
to F.

If we ever introduce local type families, this all gets a lot more
complicated, and will end up looking awfully like term-level GADT
pattern-matching.


** The new story **

Here is really what we want:

The matcher really can't deal with covars in arbitrary spots in coercions.
But it can deal with covars that are arguments to GADT data constructors.
So we somehow want to allow covars only in precisely those spots, then use
them as givens when checking the RHS. TODO (RAE): Implement plan.

Note [Quantified kind variables of a family pattern]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Consider   type family KindFam (p :: k1) (q :: k1)
           data T :: Maybe k1 -> k2 -> *
           type instance KindFam (a :: Maybe k) b = T a b -> Int
The HsBSig for the family patterns will be ([k], [a])

Then in the family instance we want to
  * Bring into scope [ "k" -> k:*, "a" -> a:k ]
  * Kind-check the RHS
  * Quantify the type instance over k and k', as well as a,b, thus
       type instance [k, k', a:Maybe k, b:k']
                     KindFam (Maybe k) k' a b = T k k' a b -> Int

Notice that in the third step we quantify over all the visibly-mentioned
type variables (a,b), but also over the implicitly mentioned kind variables
(k, k').  In this case one is bound explicitly but often there will be
none. The role of the kind signature (a :: Maybe k) is to add a constraint
that 'a' must have that kind, and to bring 'k' into scope.



************************************************************************
*                                                                      *
               Data types
*                                                                      *
************************************************************************
-}

dataDeclChecks :: Name -> NewOrData
               -> LHsContext GhcRn -> [LConDecl GhcRn]
               -> TcM Bool
dataDeclChecks :: Name
-> NewOrData
-> GenLocated SrcSpan (HsContext GhcRn)
-> [LConDecl GhcRn]
-> TcRnIf TcGblEnv TcLclEnv Bool
dataDeclChecks Name
tc_name NewOrData
new_or_data (L SrcSpan
_ HsContext GhcRn
stupid_theta) [LConDecl GhcRn]
cons
  = do {   -- Check that we don't use GADT syntax in H98 world
         Bool
gadtSyntax_ok <- Extension -> TcRnIf TcGblEnv TcLclEnv Bool
forall gbl lcl. Extension -> TcRnIf gbl lcl Bool
xoptM Extension
LangExt.GADTSyntax
       ; let gadt_syntax :: Bool
gadt_syntax = [LConDecl GhcRn] -> Bool
consUseGadtSyntax [LConDecl GhcRn]
cons
       ; Bool -> SDoc -> TcRn ()
checkTc (Bool
gadtSyntax_ok Bool -> Bool -> Bool
|| Bool -> Bool
not Bool
gadt_syntax) (Name -> SDoc
badGadtDecl Name
tc_name)

           -- Check that the stupid theta is empty for a GADT-style declaration
       ; Bool -> SDoc -> TcRn ()
checkTc (HsContext GhcRn -> Bool
forall (t :: * -> *) a. Foldable t => t a -> Bool
null HsContext GhcRn
stupid_theta Bool -> Bool -> Bool
|| Bool -> Bool
not Bool
gadt_syntax) (Name -> SDoc
badStupidTheta Name
tc_name)

         -- Check that a newtype has exactly one constructor
         -- Do this before checking for empty data decls, so that
         -- we don't suggest -XEmptyDataDecls for newtypes
       ; Bool -> SDoc -> TcRn ()
checkTc (NewOrData
new_or_data NewOrData -> NewOrData -> Bool
forall a. Eq a => a -> a -> Bool
== NewOrData
DataType Bool -> Bool -> Bool
|| [LConDecl GhcRn] -> Bool
forall a. [a] -> Bool
isSingleton [LConDecl GhcRn]
cons)
                (Name -> Arity -> SDoc
newtypeConError Name
tc_name ([LConDecl GhcRn] -> Arity
forall (t :: * -> *) a. Foldable t => t a -> Arity
length [LConDecl GhcRn]
cons))

         -- Check that there's at least one condecl,
         -- or else we're reading an hs-boot file, or -XEmptyDataDecls
       ; Bool
empty_data_decls <- Extension -> TcRnIf TcGblEnv TcLclEnv Bool
forall gbl lcl. Extension -> TcRnIf gbl lcl Bool
xoptM Extension
LangExt.EmptyDataDecls
       ; Bool
is_boot <- TcRnIf TcGblEnv TcLclEnv Bool
tcIsHsBootOrSig  -- Are we compiling an hs-boot file?
       ; Bool -> SDoc -> TcRn ()
checkTc (Bool -> Bool
not ([LConDecl GhcRn] -> Bool
forall (t :: * -> *) a. Foldable t => t a -> Bool
null [LConDecl GhcRn]
cons) Bool -> Bool -> Bool
|| Bool
empty_data_decls Bool -> Bool -> Bool
|| Bool
is_boot)
                 (Name -> SDoc
emptyConDeclsErr Name
tc_name)
       ; Bool -> TcRnIf TcGblEnv TcLclEnv Bool
forall (m :: * -> *) a. Monad m => a -> m a
return Bool
gadt_syntax }


-----------------------------------
consUseGadtSyntax :: [LConDecl GhcRn] -> Bool
consUseGadtSyntax :: [LConDecl GhcRn] -> Bool
consUseGadtSyntax (L SrcSpan
_ (ConDeclGADT {}) : [LConDecl GhcRn]
_) = Bool
True
consUseGadtSyntax [LConDecl GhcRn]
_                          = Bool
False
                 -- All constructors have same shape

-----------------------------------
tcConDecls :: KnotTied TyCon -> NewOrData
           -> [TyConBinder] -> TcKind   -- binders and result kind of tycon
           -> KnotTied Type -> [LConDecl GhcRn] -> TcM [DataCon]
tcConDecls :: TyCon
-> NewOrData
-> [TyConBinder]
-> Type
-> Type
-> [LConDecl GhcRn]
-> TcM [DataCon]
tcConDecls TyCon
rep_tycon NewOrData
new_or_data [TyConBinder]
tmpl_bndrs Type
res_kind Type
res_tmpl
  = (LConDecl GhcRn -> TcM [DataCon])
-> [LConDecl GhcRn] -> TcM [DataCon]
forall (m :: * -> *) a b. Monad m => (a -> m [b]) -> [a] -> m [b]
concatMapM ((LConDecl GhcRn -> TcM [DataCon])
 -> [LConDecl GhcRn] -> TcM [DataCon])
-> (LConDecl GhcRn -> TcM [DataCon])
-> [LConDecl GhcRn]
-> TcM [DataCon]
forall a b. (a -> b) -> a -> b
$ (ConDecl GhcRn -> TcM [DataCon]) -> LConDecl GhcRn -> TcM [DataCon]
forall a b. (a -> TcM b) -> Located a -> TcM b
addLocM ((ConDecl GhcRn -> TcM [DataCon])
 -> LConDecl GhcRn -> TcM [DataCon])
-> (ConDecl GhcRn -> TcM [DataCon])
-> LConDecl GhcRn
-> TcM [DataCon]
forall a b. (a -> b) -> a -> b
$
    TyCon
-> NameEnv Arity
-> [TyConBinder]
-> Type
-> Type
-> NewOrData
-> ConDecl GhcRn
-> TcM [DataCon]
tcConDecl TyCon
rep_tycon (TyCon -> NameEnv Arity
mkTyConTagMap TyCon
rep_tycon)
              [TyConBinder]
tmpl_bndrs Type
res_kind Type
res_tmpl NewOrData
new_or_data
    -- It's important that we pay for tag allocation here, once per TyCon,
    -- See Note [Constructor tag allocation], fixes #14657

tcConDecl :: KnotTied TyCon          -- Representation tycon. Knot-tied!
          -> NameEnv ConTag
          -> [TyConBinder] -> TcKind   -- tycon binders and result kind
          -> KnotTied Type
                 -- Return type template (T tys), where T is the family TyCon
          -> NewOrData
          -> ConDecl GhcRn
          -> TcM [DataCon]

tcConDecl :: TyCon
-> NameEnv Arity
-> [TyConBinder]
-> Type
-> Type
-> NewOrData
-> ConDecl GhcRn
-> TcM [DataCon]
tcConDecl TyCon
rep_tycon NameEnv Arity
tag_map [TyConBinder]
tmpl_bndrs Type
res_kind Type
res_tmpl NewOrData
new_or_data
          (ConDeclH98 { con_name :: forall pass. ConDecl pass -> Located (IdP pass)
con_name = GenLocated SrcSpan (IdP GhcRn)
name
                      , con_ex_tvs :: forall pass. ConDecl pass -> [LHsTyVarBndr Specificity pass]
con_ex_tvs = [LHsTyVarBndr Specificity GhcRn]
explicit_tkv_nms
                      , con_mb_cxt :: forall pass. ConDecl pass -> Maybe (LHsContext pass)
con_mb_cxt = Maybe (GenLocated SrcSpan (HsContext GhcRn))
hs_ctxt
                      , con_args :: forall pass. ConDecl pass -> HsConDeclDetails pass
con_args = HsConDeclDetails GhcRn
hs_args })
  = SDoc -> TcM [DataCon] -> TcM [DataCon]
forall a. SDoc -> TcM a -> TcM a
addErrCtxt ([Located Name] -> SDoc
dataConCtxtName [Located Name
GenLocated SrcSpan (IdP GhcRn)
name]) (TcM [DataCon] -> TcM [DataCon]) -> TcM [DataCon] -> TcM [DataCon]
forall a b. (a -> b) -> a -> b
$
    do { -- NB: the tyvars from the declaration header are in scope

         -- Get hold of the existential type variables
         -- e.g. data T a = forall k (b::k) f. MkT a (f b)
         -- Here tmpl_bndrs = {a}
         --      hs_qvars = HsQTvs { hsq_implicit = {k}
         --                        , hsq_explicit = {f,b} }

       ; String -> SDoc -> TcRn ()
traceTc String
"tcConDecl 1" ([SDoc] -> SDoc
vcat [ Located Name -> SDoc
forall a. Outputable a => a -> SDoc
ppr Located Name
GenLocated SrcSpan (IdP GhcRn)
name, [LHsTyVarBndr Specificity GhcRn] -> SDoc
forall a. Outputable a => a -> SDoc
ppr [LHsTyVarBndr Specificity GhcRn]
explicit_tkv_nms ])

       ; ([VarBndr TyVar Specificity]
exp_tvbndrs, ([Type]
ctxt, [Scaled Type]
arg_tys, [FieldLabel]
field_lbls, [HsSrcBang]
stricts))
           <- TcM
  ([VarBndr TyVar Specificity],
   ([Type], [Scaled Type], [FieldLabel], [HsSrcBang]))
-> TcM
     ([VarBndr TyVar Specificity],
      ([Type], [Scaled Type], [FieldLabel], [HsSrcBang]))
forall r. TcM r -> TcM r
pushTcLevelM_                             (TcM
   ([VarBndr TyVar Specificity],
    ([Type], [Scaled Type], [FieldLabel], [HsSrcBang]))
 -> TcM
      ([VarBndr TyVar Specificity],
       ([Type], [Scaled Type], [FieldLabel], [HsSrcBang])))
-> TcM
     ([VarBndr TyVar Specificity],
      ([Type], [Scaled Type], [FieldLabel], [HsSrcBang]))
-> TcM
     ([VarBndr TyVar Specificity],
      ([Type], [Scaled Type], [FieldLabel], [HsSrcBang]))
forall a b. (a -> b) -> a -> b
$
              TcM
  ([VarBndr TyVar Specificity],
   ([Type], [Scaled Type], [FieldLabel], [HsSrcBang]))
-> TcM
     ([VarBndr TyVar Specificity],
      ([Type], [Scaled Type], [FieldLabel], [HsSrcBang]))
forall r. TcM r -> TcM r
solveEqualities                           (TcM
   ([VarBndr TyVar Specificity],
    ([Type], [Scaled Type], [FieldLabel], [HsSrcBang]))
 -> TcM
      ([VarBndr TyVar Specificity],
       ([Type], [Scaled Type], [FieldLabel], [HsSrcBang])))
-> TcM
     ([VarBndr TyVar Specificity],
      ([Type], [Scaled Type], [FieldLabel], [HsSrcBang]))
-> TcM
     ([VarBndr TyVar Specificity],
      ([Type], [Scaled Type], [FieldLabel], [HsSrcBang]))
forall a b. (a -> b) -> a -> b
$
              [LHsTyVarBndr Specificity GhcRn]
-> TcM ([Type], [Scaled Type], [FieldLabel], [HsSrcBang])
-> TcM
     ([VarBndr TyVar Specificity],
      ([Type], [Scaled Type], [FieldLabel], [HsSrcBang]))
forall flag a.
OutputableBndrFlag flag =>
[LHsTyVarBndr flag GhcRn] -> TcM a -> TcM ([VarBndr TyVar flag], a)
bindExplicitTKBndrs_Skol [LHsTyVarBndr Specificity GhcRn]
explicit_tkv_nms (TcM ([Type], [Scaled Type], [FieldLabel], [HsSrcBang])
 -> TcM
      ([VarBndr TyVar Specificity],
       ([Type], [Scaled Type], [FieldLabel], [HsSrcBang])))
-> TcM ([Type], [Scaled Type], [FieldLabel], [HsSrcBang])
-> TcM
     ([VarBndr TyVar Specificity],
      ([Type], [Scaled Type], [FieldLabel], [HsSrcBang]))
forall a b. (a -> b) -> a -> b
$
              do { [Type]
ctxt <- Maybe (GenLocated SrcSpan (HsContext GhcRn)) -> TcM [Type]
tcHsMbContext Maybe (GenLocated SrcSpan (HsContext GhcRn))
hs_ctxt
                 ; let exp_kind :: ContextKind
exp_kind = NewOrData -> Type -> ContextKind
getArgExpKind NewOrData
new_or_data Type
res_kind
                 ; [(Scaled Type, HsSrcBang)]
btys <- ContextKind
-> HsConDeclDetails GhcRn -> TcM [(Scaled Type, HsSrcBang)]
tcConArgs ContextKind
exp_kind HsConDeclDetails GhcRn
hs_args
                 ; [FieldLabel]
field_lbls <- Name -> RnM [FieldLabel]
lookupConstructorFields (Located Name -> Name
forall l e. GenLocated l e -> e
unLoc Located Name
GenLocated SrcSpan (IdP GhcRn)
name)
                 ; let ([Scaled Type]
arg_tys, [HsSrcBang]
stricts) = [(Scaled Type, HsSrcBang)] -> ([Scaled Type], [HsSrcBang])
forall a b. [(a, b)] -> ([a], [b])
unzip [(Scaled Type, HsSrcBang)]
btys
                 ; ([Type], [Scaled Type], [FieldLabel], [HsSrcBang])
-> TcM ([Type], [Scaled Type], [FieldLabel], [HsSrcBang])
forall (m :: * -> *) a. Monad m => a -> m a
return ([Type]
ctxt, [Scaled Type]
arg_tys, [FieldLabel]
field_lbls, [HsSrcBang]
stricts)
                 }

       ; let tmpl_tvs :: [TyVar]
tmpl_tvs = [TyConBinder] -> [TyVar]
forall tv argf. [VarBndr tv argf] -> [tv]
binderVars [TyConBinder]
tmpl_bndrs

         -- exp_tvs have explicit, user-written binding sites
         -- the kvs below are those kind variables entirely unmentioned by the user
         --   and discovered only by generalization

       ; [TyVar]
kvs <- Type -> TcM [TyVar]
kindGeneralizeAll ([TyVar] -> Type -> Type
mkSpecForAllTys [TyVar]
tmpl_tvs (Type -> Type) -> Type -> Type
forall a b. (a -> b) -> a -> b
$
                                   [VarBndr TyVar Specificity] -> Type -> Type
mkInvisForAllTys [VarBndr TyVar Specificity]
exp_tvbndrs (Type -> Type) -> Type -> Type
forall a b. (a -> b) -> a -> b
$
                                   [Type] -> Type -> Type
mkPhiTy [Type]
ctxt (Type -> Type) -> Type -> Type
forall a b. (a -> b) -> a -> b
$
                                   [Scaled Type] -> Type -> Type
mkVisFunTys [Scaled Type]
arg_tys (Type -> Type) -> Type -> Type
forall a b. (a -> b) -> a -> b
$
                                   Type
unitTy)
                 -- That type is a lie, of course. (It shouldn't end in ()!)
                 -- And we could construct a proper result type from the info
                 -- at hand. But the result would mention only the tmpl_tvs,
                 -- and so it just creates more work to do it right. Really,
                 -- we're only doing this to find the right kind variables to
                 -- quantify over, and this type is fine for that purpose.

             -- Zonk to Types
       ; (ZonkEnv
ze, [TyVar]
qkvs)          <- [TyVar] -> TcM (ZonkEnv, [TyVar])
zonkTyBndrs [TyVar]
kvs
       ; (ZonkEnv
ze, [VarBndr TyVar Specificity]
user_qtvbndrs) <- ZonkEnv
-> [VarBndr TyVar Specificity]
-> TcM (ZonkEnv, [VarBndr TyVar Specificity])
forall vis.
ZonkEnv
-> [VarBndr TyVar vis] -> TcM (ZonkEnv, [VarBndr TyVar vis])
zonkTyVarBindersX ZonkEnv
ze [VarBndr TyVar Specificity]
exp_tvbndrs
       ; let user_qtvs :: [TyVar]
user_qtvs       = [VarBndr TyVar Specificity] -> [TyVar]
forall tv argf. [VarBndr tv argf] -> [tv]
binderVars [VarBndr TyVar Specificity]
user_qtvbndrs
       ; [Scaled Type]
arg_tys             <- ZonkEnv -> [Scaled Type] -> TcM [Scaled Type]
zonkScaledTcTypesToTypesX ZonkEnv
ze [Scaled Type]
arg_tys
       ; [Type]
ctxt                <- ZonkEnv -> [Type] -> TcM [Type]
zonkTcTypesToTypesX ZonkEnv
ze [Type]
ctxt

       ; FamInstEnvs
fam_envs <- TcM FamInstEnvs
tcGetFamInstEnvs

       -- Can't print univ_tvs, arg_tys etc, because we are inside the knot here
       ; String -> SDoc -> TcRn ()
traceTc String
"tcConDecl 2" (Located Name -> SDoc
forall a. Outputable a => a -> SDoc
ppr Located Name
GenLocated SrcSpan (IdP GhcRn)
name SDoc -> SDoc -> SDoc
$$ [FieldLabel] -> SDoc
forall a. Outputable a => a -> SDoc
ppr [FieldLabel]
field_lbls)
       ; let
           univ_tvbs :: [VarBndr TyVar Specificity]
univ_tvbs = [TyConBinder] -> [VarBndr TyVar Specificity]
tyConInvisTVBinders [TyConBinder]
tmpl_bndrs
           univ_tvs :: [TyVar]
univ_tvs  = [VarBndr TyVar Specificity] -> [TyVar]
forall tv argf. [VarBndr tv argf] -> [tv]
binderVars [VarBndr TyVar Specificity]
univ_tvbs
           ex_tvbs :: [VarBndr TyVar Specificity]
ex_tvbs   = Specificity -> [TyVar] -> [VarBndr TyVar Specificity]
forall vis. vis -> [TyVar] -> [VarBndr TyVar vis]
mkTyVarBinders Specificity
InferredSpec [TyVar]
qkvs [VarBndr TyVar Specificity]
-> [VarBndr TyVar Specificity] -> [VarBndr TyVar Specificity]
forall a. [a] -> [a] -> [a]
++
                       [VarBndr TyVar Specificity]
user_qtvbndrs
           ex_tvs :: [TyVar]
ex_tvs    = [TyVar]
qkvs [TyVar] -> [TyVar] -> [TyVar]
forall a. [a] -> [a] -> [a]
++ [TyVar]
user_qtvs
           -- For H98 datatypes, the user-written tyvar binders are precisely
           -- the universals followed by the existentials.
           -- See Note [DataCon user type variable binders] in GHC.Core.DataCon.
           user_tvbs :: [VarBndr TyVar Specificity]
user_tvbs = [VarBndr TyVar Specificity]
univ_tvbs [VarBndr TyVar Specificity]
-> [VarBndr TyVar Specificity] -> [VarBndr TyVar Specificity]
forall a. [a] -> [a] -> [a]
++ [VarBndr TyVar Specificity]
ex_tvbs
           buildOneDataCon :: Located Name -> IOEnv (Env TcGblEnv TcLclEnv) DataCon
buildOneDataCon (L SrcSpan
_ Name
name) = do
             { Bool
is_infix <- Name -> HsConDeclDetails GhcRn -> TcRnIf TcGblEnv TcLclEnv Bool
forall a b.
Name -> HsConDetails a b -> TcRnIf TcGblEnv TcLclEnv Bool
tcConIsInfixH98 Name
name HsConDeclDetails GhcRn
hs_args
             ; Name
rep_nm   <- Name -> TcRnIf TcGblEnv TcLclEnv Name
forall gbl lcl. Name -> TcRnIf gbl lcl Name
newTyConRepName Name
name

             ; FamInstEnvs
-> Name
-> Bool
-> Name
-> [HsSrcBang]
-> Maybe [HsImplBang]
-> [FieldLabel]
-> [TyVar]
-> [TyVar]
-> [VarBndr TyVar Specificity]
-> [EqSpec]
-> [Type]
-> [Scaled Type]
-> Type
-> TyCon
-> NameEnv Arity
-> IOEnv (Env TcGblEnv TcLclEnv) DataCon
forall m n.
FamInstEnvs
-> Name
-> Bool
-> Name
-> [HsSrcBang]
-> Maybe [HsImplBang]
-> [FieldLabel]
-> [TyVar]
-> [TyVar]
-> [VarBndr TyVar Specificity]
-> [EqSpec]
-> [Type]
-> [Scaled Type]
-> Type
-> TyCon
-> NameEnv Arity
-> TcRnIf m n DataCon
buildDataCon FamInstEnvs
fam_envs Name
name Bool
is_infix Name
rep_nm
                            [HsSrcBang]
stricts Maybe [HsImplBang]
forall a. Maybe a
Nothing [FieldLabel]
field_lbls
                            [TyVar]
univ_tvs [TyVar]
ex_tvs [VarBndr TyVar Specificity]
user_tvbs
                            [{- no eq_preds -}] [Type]
ctxt [Scaled Type]
arg_tys
                            Type
res_tmpl TyCon
rep_tycon NameEnv Arity
tag_map
                  -- NB:  we put data_tc, the type constructor gotten from the
                  --      constructor type signature into the data constructor;
                  --      that way checkValidDataCon can complain if it's wrong.
             }
       ; String -> SDoc -> TcRn ()
traceTc String
"tcConDecl 2" (Located Name -> SDoc
forall a. Outputable a => a -> SDoc
ppr Located Name
GenLocated SrcSpan (IdP GhcRn)
name)
       ; (Located Name -> IOEnv (Env TcGblEnv TcLclEnv) DataCon)
-> [Located Name] -> TcM [DataCon]
forall (t :: * -> *) (m :: * -> *) a b.
(Traversable t, Monad m) =>
(a -> m b) -> t a -> m (t b)
mapM Located Name -> IOEnv (Env TcGblEnv TcLclEnv) DataCon
buildOneDataCon [Located Name
GenLocated SrcSpan (IdP GhcRn)
name]
       }

tcConDecl TyCon
rep_tycon NameEnv Arity
tag_map [TyConBinder]
tmpl_bndrs Type
_res_kind Type
res_tmpl NewOrData
new_or_data
  -- NB: don't use res_kind here, as it's ill-scoped. Instead,
  -- we get the res_kind by typechecking the result type.
          (ConDeclGADT { con_g_ext :: forall pass. ConDecl pass -> XConDeclGADT pass
con_g_ext = XConDeclGADT GhcRn
implicit_tkv_nms
                       , con_names :: forall pass. ConDecl pass -> [Located (IdP pass)]
con_names = [GenLocated SrcSpan (IdP GhcRn)]
names
                       , con_qvars :: forall pass. ConDecl pass -> [LHsTyVarBndr Specificity pass]
con_qvars = [LHsTyVarBndr Specificity GhcRn]
explicit_tkv_nms
                       , con_mb_cxt :: forall pass. ConDecl pass -> Maybe (LHsContext pass)
con_mb_cxt = Maybe (GenLocated SrcSpan (HsContext GhcRn))
cxt, con_args :: forall pass. ConDecl pass -> HsConDeclDetails pass
con_args = HsConDeclDetails GhcRn
hs_args
                       , con_res_ty :: forall pass. ConDecl pass -> LHsType pass
con_res_ty = LHsType GhcRn
hs_res_ty })
  = SDoc -> TcM [DataCon] -> TcM [DataCon]
forall a. SDoc -> TcM a -> TcM a
addErrCtxt ([Located Name] -> SDoc
dataConCtxtName [Located Name]
[GenLocated SrcSpan (IdP GhcRn)]
names) (TcM [DataCon] -> TcM [DataCon]) -> TcM [DataCon] -> TcM [DataCon]
forall a b. (a -> b) -> a -> b
$
    do { String -> SDoc -> TcRn ()
traceTc String
"tcConDecl 1 gadt" ([Located Name] -> SDoc
forall a. Outputable a => a -> SDoc
ppr [Located Name]
[GenLocated SrcSpan (IdP GhcRn)]
names)
       ; let (L SrcSpan
_ Name
name : [Located Name]
_) = [Located Name]
[GenLocated SrcSpan (IdP GhcRn)]
names

       ; ([TyVar]
imp_tvs, ([VarBndr TyVar Specificity]
exp_tvbndrs, ([Type]
ctxt, [Scaled Type]
arg_tys, Type
res_ty, [FieldLabel]
field_lbls, [HsSrcBang]
stricts)))
           <- TcM
  ([TyVar],
   ([VarBndr TyVar Specificity],
    ([Type], [Scaled Type], Type, [FieldLabel], [HsSrcBang])))
-> TcM
     ([TyVar],
      ([VarBndr TyVar Specificity],
       ([Type], [Scaled Type], Type, [FieldLabel], [HsSrcBang])))
forall r. TcM r -> TcM r
pushTcLevelM_    (TcM
   ([TyVar],
    ([VarBndr TyVar Specificity],
     ([Type], [Scaled Type], Type, [FieldLabel], [HsSrcBang])))
 -> TcM
      ([TyVar],
       ([VarBndr TyVar Specificity],
        ([Type], [Scaled Type], Type, [FieldLabel], [HsSrcBang]))))
-> TcM
     ([TyVar],
      ([VarBndr TyVar Specificity],
       ([Type], [Scaled Type], Type, [FieldLabel], [HsSrcBang])))
-> TcM
     ([TyVar],
      ([VarBndr TyVar Specificity],
       ([Type], [Scaled Type], Type, [FieldLabel], [HsSrcBang])))
forall a b. (a -> b) -> a -> b
$  -- We are going to generalise
              TcM
  ([TyVar],
   ([VarBndr TyVar Specificity],
    ([Type], [Scaled Type], Type, [FieldLabel], [HsSrcBang])))
-> TcM
     ([TyVar],
      ([VarBndr TyVar Specificity],
       ([Type], [Scaled Type], Type, [FieldLabel], [HsSrcBang])))
forall r. TcM r -> TcM r
solveEqualities  (TcM
   ([TyVar],
    ([VarBndr TyVar Specificity],
     ([Type], [Scaled Type], Type, [FieldLabel], [HsSrcBang])))
 -> TcM
      ([TyVar],
       ([VarBndr TyVar Specificity],
        ([Type], [Scaled Type], Type, [FieldLabel], [HsSrcBang]))))
-> TcM
     ([TyVar],
      ([VarBndr TyVar Specificity],
       ([Type], [Scaled Type], Type, [FieldLabel], [HsSrcBang])))
-> TcM
     ([TyVar],
      ([VarBndr TyVar Specificity],
       ([Type], [Scaled Type], Type, [FieldLabel], [HsSrcBang])))
forall a b. (a -> b) -> a -> b
$  -- We won't get another crack, and we don't
                                  -- want an error cascade
              [Name]
-> TcM
     ([VarBndr TyVar Specificity],
      ([Type], [Scaled Type], Type, [FieldLabel], [HsSrcBang]))
-> TcM
     ([TyVar],
      ([VarBndr TyVar Specificity],
       ([Type], [Scaled Type], Type, [FieldLabel], [HsSrcBang])))
forall a. [Name] -> TcM a -> TcM ([TyVar], a)
bindImplicitTKBndrs_Skol [Name]
XConDeclGADT GhcRn
implicit_tkv_nms (TcM
   ([VarBndr TyVar Specificity],
    ([Type], [Scaled Type], Type, [FieldLabel], [HsSrcBang]))
 -> TcM
      ([TyVar],
       ([VarBndr TyVar Specificity],
        ([Type], [Scaled Type], Type, [FieldLabel], [HsSrcBang]))))
-> TcM
     ([VarBndr TyVar Specificity],
      ([Type], [Scaled Type], Type, [FieldLabel], [HsSrcBang]))
-> TcM
     ([TyVar],
      ([VarBndr TyVar Specificity],
       ([Type], [Scaled Type], Type, [FieldLabel], [HsSrcBang])))
forall a b. (a -> b) -> a -> b
$
              [LHsTyVarBndr Specificity GhcRn]
-> TcM ([Type], [Scaled Type], Type, [FieldLabel], [HsSrcBang])
-> TcM
     ([VarBndr TyVar Specificity],
      ([Type], [Scaled Type], Type, [FieldLabel], [HsSrcBang]))
forall flag a.
OutputableBndrFlag flag =>
[LHsTyVarBndr flag GhcRn] -> TcM a -> TcM ([VarBndr TyVar flag], a)
bindExplicitTKBndrs_Skol [LHsTyVarBndr Specificity GhcRn]
explicit_tkv_nms (TcM ([Type], [Scaled Type], Type, [FieldLabel], [HsSrcBang])
 -> TcM
      ([VarBndr TyVar Specificity],
       ([Type], [Scaled Type], Type, [FieldLabel], [HsSrcBang])))
-> TcM ([Type], [Scaled Type], Type, [FieldLabel], [HsSrcBang])
-> TcM
     ([VarBndr TyVar Specificity],
      ([Type], [Scaled Type], Type, [FieldLabel], [HsSrcBang]))
forall a b. (a -> b) -> a -> b
$
              do { [Type]
ctxt <- Maybe (GenLocated SrcSpan (HsContext GhcRn)) -> TcM [Type]
tcHsMbContext Maybe (GenLocated SrcSpan (HsContext GhcRn))
cxt
                 ; (Type
res_ty, Type
res_kind) <- LHsType GhcRn -> TcM (Type, Type)
tcInferLHsTypeKind LHsType GhcRn
hs_res_ty
                         -- See Note [GADT return kinds]

                   -- See Note [Datatype return kinds]
                 ; let exp_kind :: ContextKind
exp_kind = NewOrData -> Type -> ContextKind
getArgExpKind NewOrData
new_or_data Type
res_kind

                 ;