\begin{code}
module TcHsType (
- tcHsSigType, tcHsDeriv,
+ tcHsSigType, tcHsSigTypeNC, tcHsDeriv,
tcHsInstHead, tcHsQuantifiedType,
UserTypeCtxt(..),
-- Kind checking
kcHsTyVars, kcHsSigType, kcHsLiftedSigType,
- kcCheckHsType, kcHsContext, kcHsType,
+ kcLHsType, kcCheckLHsType, kcHsContext,
-- Typechecking kinded types
tcHsKindedContext, tcHsKindedType, tcHsBangType,
- tcTyVarBndrs, dsHsType, tcLHsConResTy,
- tcDataKindSig,
+ tcTyVarBndrs, dsHsType,
+ tcDataKindSig, ExpKind(..), EkCtxt(..),
-- Pattern type signatures
tcHsPatSigType, tcPatSig
#include "HsVersions.h"
+#ifdef GHCI /* Only if bootstrapped */
+import {-# SOURCE #-} TcSplice( kcSpliceType )
+#endif
+
import HsSyn
import RnHsSyn
import TcRnMonad
import TcType
import {- Kind parts of -} Type
import Var
+import VarSet
import Coercion
import TyCon
import Class
import Name
-import OccName
import NameSet
import PrelNames
import TysWiredIn
import BasicTypes
import SrcLoc
+import Util
import UniqSupply
import Outputable
import FastString
-
-import Control.Monad
\end{code}
%************************************************************************
\begin{code}
-tcHsSigType :: UserTypeCtxt -> LHsType Name -> TcM Type
+tcHsSigType, tcHsSigTypeNC :: UserTypeCtxt -> LHsType Name -> TcM Type
-- Do kind checking, and hoist for-alls to the top
-- NB: it's important that the foralls that come from the top-level
-- HsForAllTy in hs_ty occur *first* in the returned type.
-- See Note [Scoped] with TcSigInfo
tcHsSigType ctxt hs_ty
= addErrCtxt (pprHsSigCtxt ctxt hs_ty) $
- do { kinded_ty <- kcTypeType hs_ty
+ tcHsSigTypeNC ctxt hs_ty
+
+tcHsSigTypeNC ctxt hs_ty
+ = do { (kinded_ty, _kind) <- kc_lhs_type hs_ty
+ -- The kind is checked by checkValidType, and isn't necessarily
+ -- of kind * in a Template Haskell quote eg [t| Maybe |]
; ty <- tcHsKindedType kinded_ty
; checkValidType ctxt ty
; return ty }
tcHsInstHead :: LHsType Name -> TcM ([TyVar], ThetaType, Type)
-- Typecheck an instance head. We can't use
-- tcHsSigType, because it's not a valid user type.
-tcHsInstHead hs_ty
- = do { kinded_ty <- kcHsSigType hs_ty
- ; poly_ty <- tcHsKindedType kinded_ty
- ; return (tcSplitSigmaTy poly_ty) }
+tcHsInstHead (L loc ty)
+ = setSrcSpan loc $ -- No need for an "In the type..." context
+ tc_inst_head ty -- because that comes from the caller
+ where
+ -- tc_inst_head expects HsPredTy, which isn't usually even allowed
+ tc_inst_head (HsPredTy pred)
+ = do { pred' <- kcHsPred pred
+ ; pred'' <- dsHsPred pred'
+ ; return ([], [], mkPredTy pred'') }
+
+ tc_inst_head (HsForAllTy _ tvs ctxt (L _ (HsPredTy pred)))
+ = kcHsTyVars tvs $ \ tvs' ->
+ do { ctxt' <- kcHsContext ctxt
+ ; pred' <- kcHsPred pred
+ ; tcTyVarBndrs tvs' $ \ tvs'' ->
+ do { ctxt'' <- mapM dsHsLPred (unLoc ctxt')
+ ; pred'' <- dsHsPred pred'
+ ; return (tvs'', ctxt'', mkPredTy pred'') } }
+
+ tc_inst_head _ = failWithTc (ptext (sLit "Malformed instance type"))
tcHsQuantifiedType :: [LHsTyVarBndr Name] -> LHsType Name -> TcM ([TyVar], Type)
-- Behave very like type-checking (HsForAllTy sig_tvs hs_ty),
tc_hs_deriv tv_names (HsPredTy (HsClassP cls_name hs_tys))
= kcHsTyVars tv_names $ \ tv_names' ->
do { cls_kind <- kcClass cls_name
- ; (tys, _res_kind) <- kcApps cls_kind (ppr cls_name) hs_tys
+ ; (tys, _res_kind) <- kcApps cls_name cls_kind hs_tys
; tcTyVarBndrs tv_names' $ \ tyvars ->
do { arg_tys <- dsHsTypes tys
; cls <- tcLookupClass cls_name
\begin{code}
kcHsSigType, kcHsLiftedSigType :: LHsType Name -> TcM (LHsType Name)
-- Used for type signatures
-kcHsSigType ty = kcTypeType ty
-kcHsLiftedSigType ty = kcLiftedType ty
+kcHsSigType ty = addKcTypeCtxt ty $ kcTypeType ty
+kcHsLiftedSigType ty = addKcTypeCtxt ty $ kcLiftedType ty
tcHsKindedType :: LHsType Name -> TcM Type
-- Don't do kind checking, nor validity checking.
---------------------------
kcLiftedType :: LHsType Name -> TcM (LHsType Name)
-- The type ty must be a *lifted* *type*
-kcLiftedType ty = kcCheckHsType ty liftedTypeKind
+kcLiftedType ty = kc_check_lhs_type ty ekLifted
---------------------------
kcTypeType :: LHsType Name -> TcM (LHsType Name)
-- The type ty must be a *type*, but it can be lifted or
-- unlifted or an unboxed tuple.
-kcTypeType ty = kcCheckHsType ty openTypeKind
+kcTypeType ty = kc_check_lhs_type ty ekOpen
---------------------------
-kcCheckHsType :: LHsType Name -> TcKind -> TcM (LHsType Name)
+kcCheckLHsType :: LHsType Name -> ExpKind -> TcM (LHsType Name)
+kcCheckLHsType ty kind = addKcTypeCtxt ty $ kc_check_lhs_type ty kind
+
+
+kc_check_lhs_type :: LHsType Name -> ExpKind -> TcM (LHsType Name)
-- Check that the type has the specified kind
-- Be sure to use checkExpectedKind, rather than simply unifying
-- with OpenTypeKind, because it gives better error messages
-kcCheckHsType (L span ty) exp_kind
- = setSrcSpan span $
- do { (ty', act_kind) <- add_ctxt ty (kc_hs_type ty)
+kc_check_lhs_type (L span ty) exp_kind
+ = setSrcSpan span $
+ do { ty' <- kc_check_hs_type ty exp_kind
+ ; return (L span ty') }
+
+kc_check_lhs_types :: [(LHsType Name, ExpKind)] -> TcM [LHsType Name]
+kc_check_lhs_types tys_w_kinds
+ = mapM kc_arg tys_w_kinds
+ where
+ kc_arg (arg, arg_kind) = kc_check_lhs_type arg arg_kind
+
+
+---------------------------
+kc_check_hs_type :: HsType Name -> ExpKind -> TcM (HsType Name)
+
+-- First some special cases for better error messages
+-- when we know the expected kind
+kc_check_hs_type (HsParTy ty) exp_kind
+ = do { ty' <- kc_check_lhs_type ty exp_kind; return (HsParTy ty') }
+
+kc_check_hs_type ty@(HsAppTy ty1 ty2) exp_kind
+ = do { let (fun_ty, arg_tys) = splitHsAppTys ty1 ty2
+ ; (fun_ty', fun_kind) <- kc_lhs_type fun_ty
+ ; arg_tys' <- kcCheckApps fun_ty fun_kind arg_tys ty exp_kind
+ ; return (mkHsAppTys fun_ty' arg_tys') }
+
+-- This is the general case: infer the kind and compare
+kc_check_hs_type ty exp_kind
+ = do { (ty', act_kind) <- kc_hs_type ty
-- Add the context round the inner check only
-- because checkExpectedKind already mentions
-- 'ty' by name in any error message
; checkExpectedKind (strip ty) act_kind exp_kind
- ; return (L span ty') }
+ ; return ty' }
where
- -- Wrap a context around only if we want to show that contexts.
- add_ctxt (HsPredTy _) thing = thing
- -- Omit invisble ones and ones user's won't grok (HsPred p).
- add_ctxt (HsForAllTy _ _ (L _ []) _) thing = thing
- -- Omit wrapping if the theta-part is empty
- -- Reason: the recursive call to kcLiftedType, in the ForAllTy
- -- case of kc_hs_type, will do the wrapping instead
- -- and we don't want to duplicate
- add_ctxt other_ty thing = addErrCtxt (typeCtxt other_ty) thing
-
-- We infer the kind of the type, and then complain if it's
-- not right. But we don't want to complain about
-- (ty) or !(ty) or forall a. ty
Here comes the main function
\begin{code}
-kcHsType :: LHsType Name -> TcM (LHsType Name, TcKind)
-kcHsType ty = wrapLocFstM kc_hs_type ty
--- kcHsType *returns* the kind of the type, rather than taking an expected
+kcLHsType :: LHsType Name -> TcM (LHsType Name, TcKind)
+-- Called from outside: set the context
+kcLHsType ty = addKcTypeCtxt ty (kc_lhs_type ty)
+
+kc_lhs_type :: LHsType Name -> TcM (LHsType Name, TcKind)
+kc_lhs_type (L span ty)
+ = setSrcSpan span $
+ do { (ty', kind) <- kc_hs_type ty
+ ; return (L span ty', kind) }
+
+-- kc_hs_type *returns* the kind of the type, rather than taking an expected
-- kind as argument as tcExpr does.
-- Reasons:
-- (a) the kind of (->) is
kc_hs_type :: HsType Name -> TcM (HsType Name, TcKind)
kc_hs_type (HsParTy ty) = do
- (ty', kind) <- kcHsType ty
+ (ty', kind) <- kc_lhs_type ty
return (HsParTy ty', kind)
kc_hs_type (HsTyVar name) = do
= return (HsNumTy n, liftedTypeKind)
kc_hs_type (HsKindSig ty k) = do
- ty' <- kcCheckHsType ty k
+ ty' <- kc_check_lhs_type ty (EK k EkKindSig)
return (HsKindSig ty' k, k)
kc_hs_type (HsTupleTy Boxed tys) = do
return (HsTupleTy Unboxed tys', ubxTupleKind)
kc_hs_type (HsFunTy ty1 ty2) = do
- ty1' <- kcCheckHsType ty1 argTypeKind
+ ty1' <- kc_check_lhs_type ty1 (EK argTypeKind EkUnk)
ty2' <- kcTypeType ty2
return (HsFunTy ty1' ty2', liftedTypeKind)
kc_hs_type (HsOpTy ty1 op ty2) = do
op_kind <- addLocM kcTyVar op
- ([ty1',ty2'], res_kind) <- kcApps op_kind (ppr op) [ty1,ty2]
+ ([ty1',ty2'], res_kind) <- kcApps op op_kind [ty1,ty2]
return (HsOpTy ty1' op ty2', res_kind)
kc_hs_type (HsAppTy ty1 ty2) = do
- (fun_ty', fun_kind) <- kcHsType fun_ty
- ((arg_ty':arg_tys'), res_kind) <- kcApps fun_kind (ppr fun_ty) arg_tys
- return (foldl mk_app (HsAppTy fun_ty' arg_ty') arg_tys', res_kind)
+ (fun_ty', fun_kind) <- kc_lhs_type fun_ty
+ (arg_tys', res_kind) <- kcApps fun_ty fun_kind arg_tys
+ return (mkHsAppTys fun_ty' arg_tys', res_kind)
where
- (fun_ty, arg_tys) = split ty1 [ty2]
- split (L _ (HsAppTy f a)) as = split f (a:as)
- split f as = (f,as)
- mk_app fun arg = HsAppTy (noLoc fun) arg -- Add noLocs for inner nodes of
- -- the application; they are
- -- never used
+ (fun_ty, arg_tys) = splitHsAppTys ty1 ty2
-kc_hs_type (HsPredTy (HsEqualP _ _))
- = wrongEqualityErr
+kc_hs_type (HsPredTy pred)
+ = wrongPredErr pred
-kc_hs_type (HsPredTy pred) = do
- pred' <- kcHsPred pred
- return (HsPredTy pred', liftedTypeKind)
+kc_hs_type (HsCoreTy ty)
+ = return (HsCoreTy ty, typeKind ty)
kc_hs_type (HsForAllTy exp tv_names context ty)
= kcHsTyVars tv_names $ \ tv_names' ->
; return (HsForAllTy exp tv_names' ctxt' ty', liftedTypeKind) }
-kc_hs_type (HsBangTy b ty) = do
- (ty', kind) <- kcHsType ty
- return (HsBangTy b ty', kind)
+kc_hs_type (HsBangTy b ty)
+ = do { (ty', kind) <- kc_lhs_type ty
+ ; return (HsBangTy b ty', kind) }
-kc_hs_type ty@(HsSpliceTy _)
- = failWithTc (ptext (sLit "Unexpected type splice:") <+> ppr ty)
+kc_hs_type ty@(HsRecTy _)
+ = failWithTc (ptext (sLit "Unexpected record type") <+> ppr ty)
+ -- Record types (which only show up temporarily in constructor signatures)
+ -- should have been removed by now
+
+#ifdef GHCI /* Only if bootstrapped */
+kc_hs_type (HsSpliceTy sp fvs _) = kcSpliceType sp fvs
+#else
+kc_hs_type ty@(HsSpliceTy {}) = failWithTc (ptext (sLit "Unexpected type splice:") <+> ppr ty)
+#endif
+
+kc_hs_type (HsQuasiQuoteTy {}) = panic "kc_hs_type" -- Eliminated by renamer
-- remove the doc nodes here, no need to worry about the location since
-- its the same for a doc node and it's child type node
= kc_hs_type (unLoc ty)
---------------------------
-kcApps :: TcKind -- Function kind
- -> SDoc -- Function
+kcApps :: Outputable a
+ => a
+ -> TcKind -- Function kind
-> [LHsType Name] -- Arg types
-> TcM ([LHsType Name], TcKind) -- Kind-checked args
-kcApps fun_kind ppr_fun args = do
- (arg_kinds, res_kind) <- split_fk fun_kind (length args)
- args' <- zipWithM kc_arg args arg_kinds
- return (args', res_kind)
+kcApps the_fun fun_kind args
+ = do { (args_w_kinds, res_kind) <- splitFunKind (ppr the_fun) 1 fun_kind args
+ ; args' <- kc_check_lhs_types args_w_kinds
+ ; return (args', res_kind) }
+
+kcCheckApps :: Outputable a => a -> TcKind -> [LHsType Name]
+ -> HsType Name -- The type being checked (for err messages only)
+ -> ExpKind -- Expected kind
+ -> TcM [LHsType Name]
+kcCheckApps the_fun fun_kind args ty exp_kind
+ = do { (args_w_kinds, res_kind) <- splitFunKind (ppr the_fun) 1 fun_kind args
+ ; checkExpectedKind ty res_kind exp_kind
+ -- Check the result kind *before* checking argument kinds
+ -- This improves error message; Trac #2994
+ ; kc_check_lhs_types args_w_kinds }
+
+splitHsAppTys :: LHsType Name -> LHsType Name -> (LHsType Name, [LHsType Name])
+splitHsAppTys fun_ty arg_ty = split fun_ty [arg_ty]
where
- split_fk fk 0 = return ([], fk)
- split_fk fk n = do mb_fk <- unifyFunKind fk
- case mb_fk of
- Nothing -> failWithTc too_many_args
- Just (ak,fk') -> do (aks, rk) <- split_fk fk' (n-1)
- return (ak:aks, rk)
+ split (L _ (HsAppTy f a)) as = split f (a:as)
+ split f as = (f,as)
- kc_arg arg arg_kind = kcCheckHsType arg arg_kind
+mkHsAppTys :: LHsType Name -> [LHsType Name] -> HsType Name
+mkHsAppTys fun_ty [] = pprPanic "mkHsAppTys" (ppr fun_ty)
+mkHsAppTys fun_ty (arg_ty:arg_tys)
+ = foldl mk_app (HsAppTy fun_ty arg_ty) arg_tys
+ where
+ mk_app fun arg = HsAppTy (noLoc fun) arg -- Add noLocs for inner nodes of
+ -- the application; they are
+ -- never used
- too_many_args = ptext (sLit "Kind error:") <+> quotes ppr_fun <+>
+---------------------------
+splitFunKind :: SDoc -> Int -> TcKind -> [b] -> TcM ([(b,ExpKind)], TcKind)
+splitFunKind _ _ fk [] = return ([], fk)
+splitFunKind the_fun arg_no fk (arg:args)
+ = do { mb_fk <- unifyFunKind fk
+ ; case mb_fk of
+ Nothing -> failWithTc too_many_args
+ Just (ak,fk') -> do { (aks, rk) <- splitFunKind the_fun (arg_no+1) fk' args
+ ; return ((arg, EK ak (EkArg the_fun arg_no)):aks, rk) } }
+ where
+ too_many_args = quotes the_fun <+>
ptext (sLit "is applied to too many type arguments")
---------------------------
kcHsPred :: HsPred Name -> TcM (HsPred Name)
kcHsPred pred = do -- Checks that the result is of kind liftedType
(pred', kind) <- kc_pred pred
- checkExpectedKind pred kind liftedTypeKind
+ checkExpectedKind pred kind ekLifted
return pred'
---------------------------
-- Does *not* check for a saturated
-- application (reason: used from TcDeriv)
kc_pred (HsIParam name ty)
- = do { (ty', kind) <- kcHsType ty
+ = do { (ty', kind) <- kc_lhs_type ty
; return (HsIParam name ty', kind)
}
kc_pred (HsClassP cls tys)
= do { kind <- kcClass cls
- ; (tys', res_kind) <- kcApps kind (ppr cls) tys
+ ; (tys', res_kind) <- kcApps cls kind tys
; return (HsClassP cls tys', res_kind)
}
kc_pred (HsEqualP ty1 ty2)
- = do { (ty1', kind1) <- kcHsType ty1
+ = do { (ty1', kind1) <- kc_lhs_type ty1
-- ; checkExpectedKind ty1 kind1 liftedTypeKind
- ; (ty2', kind2) <- kcHsType ty2
+ ; (ty2', kind2) <- kc_lhs_type ty2
-- ; checkExpectedKind ty2 kind2 liftedTypeKind
- ; checkExpectedKind ty2 kind2 kind1
+ ; checkExpectedKind ty2 kind2 (EK kind1 EkEqPred)
; return (HsEqualP ty1' ty2', liftedTypeKind)
}
ds_type (HsParTy ty) -- Remove the parentheses markers
= dsHsType ty
-ds_type ty@(HsBangTy _ _) -- No bangs should be here
+ds_type ty@(HsBangTy {}) -- No bangs should be here
= failWithTc (ptext (sLit "Unexpected strictness annotation:") <+> ppr ty)
+ds_type ty@(HsRecTy {}) -- No bangs should be here
+ = failWithTc (ptext (sLit "Unexpected record type:") <+> ppr ty)
+
ds_type (HsKindSig ty _)
= dsHsType ty -- Kind checking done already
tau <- dsHsType ty
return (mkSigmaTy tyvars theta tau)
-ds_type (HsSpliceTy {}) = panic "ds_type: HsSpliceTy"
-
ds_type (HsDocTy ty _) -- Remove the doc comment
= dsHsType ty
+ds_type (HsSpliceTy _ _ kind)
+ = do { kind' <- zonkTcKindToKind kind
+ ; newFlexiTyVarTy kind' }
+
+ds_type (HsQuasiQuoteTy {}) = panic "ds_type" -- Eliminated by renamer
+ds_type (HsCoreTy ty) = return ty
+
dsHsTypes :: [LHsType Name] -> TcM [Type]
dsHsTypes arg_tys = mapM dsHsType arg_tys
\end{code}
}
\end{code}
-GADT constructor signatures
-
\begin{code}
-tcLHsConResTy :: LHsType Name -> TcM (TyCon, [TcType])
-tcLHsConResTy (L span res_ty)
- = setSrcSpan span $
- case get_args res_ty [] of
- (HsTyVar tc_name, args)
- -> do { args' <- mapM dsHsType args
- ; thing <- tcLookup tc_name
- ; case thing of
- AGlobal (ATyCon tc) -> return (tc, args')
- _ -> failWithTc (badGadtDecl res_ty) }
- _ -> failWithTc (badGadtDecl res_ty)
- where
- -- We can't call dsHsType on res_ty, and then do tcSplitTyConApp_maybe
- -- because that causes a black hole, and for good reason. Building
- -- the type means expanding type synonyms, and we can't do that
- -- inside the "knot". So we have to work by steam.
- get_args (HsAppTy (L _ fun) arg) args = get_args fun (arg:args)
- get_args (HsParTy (L _ ty)) args = get_args ty args
- get_args (HsOpTy ty1 (L _ tc) ty2) args = (HsTyVar tc, ty1:ty2:args)
- get_args ty args = (ty, args)
-
-badGadtDecl :: HsType Name -> SDoc
-badGadtDecl ty
- = hang (ptext (sLit "Malformed constructor result type:"))
- 2 (ppr ty)
+addKcTypeCtxt :: LHsType Name -> TcM a -> TcM a
+ -- Wrap a context around only if we want to show that contexts.
+addKcTypeCtxt (L _ (HsPredTy _)) thing = thing
+ -- Omit invisble ones and ones user's won't grok (HsPred p).
+addKcTypeCtxt (L _ other_ty) thing = addErrCtxt (typeCtxt other_ty) thing
typeCtxt :: HsType Name -> SDoc
typeCtxt ty = ptext (sLit "In the type") <+> quotes (ppr ty)
-> ([LHsTyVarBndr Name] -> TcM r) -- These binders are kind-annotated
-- They scope over the thing inside
-> TcM r
-kcHsTyVars tvs thing_inside = do
- bndrs <- mapM (wrapLocM kcHsTyVar) tvs
- tcExtendKindEnvTvs bndrs (thing_inside bndrs)
+kcHsTyVars tvs thing_inside
+ = do { kinded_tvs <- mapM (wrapLocM kcHsTyVar) tvs
+ ; tcExtendKindEnvTvs kinded_tvs thing_inside }
kcHsTyVar :: HsTyVarBndr Name -> TcM (HsTyVarBndr Name)
-- Return a *kind-annotated* binder, and a tyvar with a mutable kind in it
-kcHsTyVar (UserTyVar name) = KindedTyVar name <$> newKindVar
-kcHsTyVar (KindedTyVar name kind) = return (KindedTyVar name kind)
+kcHsTyVar (UserTyVar name _) = UserTyVar name <$> newKindVar
+kcHsTyVar tv@(KindedTyVar {}) = return tv
------------------
tcTyVarBndrs :: [LHsTyVarBndr Name] -- Kind-annotated binders, which need kind-zonking
tyvars <- mapM (zonk . unLoc) bndrs
tcExtendTyVarEnv tyvars (thing_inside tyvars)
where
- zonk (KindedTyVar name kind) = do { kind' <- zonkTcKindToKind kind
- ; return (mkTyVar name kind') }
- zonk (UserTyVar name) = WARN( True, ptext (sLit "Un-kinded tyvar") <+> ppr name )
- return (mkTyVar name liftedTypeKind)
+ zonk (UserTyVar name kind) = do { kind' <- zonkTcKindToKind kind
+ ; return (mkTyVar name kind') }
+ zonk (KindedTyVar name kind) = return (mkTyVar name kind)
-----------------------------------
tcDataKindSig :: Maybe Kind -> TcM [TyVar]
; us <- newUniqueSupply
; let uniqs = uniqsFromSupply us
; return [ mk_tv span uniq str kind
- | ((kind, str), uniq) <- arg_kinds `zip` names `zip` uniqs ] }
+ | ((kind, str), uniq) <- arg_kinds `zip` dnames `zip` uniqs ] }
where
(arg_kinds, res_kind) = splitKindFunTys kind
mk_tv loc uniq str kind = mkTyVar name kind
where
name = mkInternalName uniq occ loc
occ = mkOccName tvName str
+
+ dnames = map ('$' :) names -- Note [Avoid name clashes for associated data types]
- names :: [String] -- a,b,c...aa,ab,ac etc
+ names :: [String]
names = [ c:cs | cs <- "" : names, c <- ['a'..'z'] ]
badKindSig :: Kind -> SDoc
2 (ppr kind)
\end{code}
+Note [Avoid name clashes for associated data types]
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+Consider class C a b where
+ data D b :: * -> *
+When typechecking the decl for D, we'll invent an extra type variable for D,
+to fill out its kind. We *don't* want this type variable to be 'a', because
+in an .hi file we'd get
+ class C a b where
+ data D b a
+which makes it look as if there are *two* type indices. But there aren't!
+So we use $a instead, which cannot clash with a user-written type variable.
+Remember that type variable binders in interface files are just FastStrings,
+not proper Names.
+
+(The tidying phase can't help here because we don't tidy TyCons. Another
+alternative would be to record the number of indexing parameters in the
+interface file.)
+
%************************************************************************
%* *
-- should be bound by the pattern signature
in_scope <- getInLocalScope
; let span = getLoc hs_ty
- sig_tvs = [ L span (UserTyVar n)
- | n <- nameSetToList (extractHsTyVars hs_ty),
- not (in_scope n) ]
+ sig_tvs = userHsTyVarBndrs $ map (L span) $
+ filterOut in_scope $
+ nameSetToList (extractHsTyVars hs_ty)
; (tyvars, sig_ty) <- tcHsQuantifiedType sig_tvs hs_ty
; checkValidType ctxt sig_ty
-- Check that pat_ty is rigid
; checkTc (isRigidTy res_ty) (wobblyPatSig sig_tvs)
+ -- Check that all newly-in-scope tyvars are in fact
+ -- constrained by the pattern. This catches tiresome
+ -- cases like
+ -- type T a = Int
+ -- f :: Int -> Int
+ -- f (x :: T a) = ...
+ -- Here 'a' doesn't get a binding. Sigh
+ ; let bad_tvs = filterOut (`elemVarSet` exactTyVarsOfType sig_ty) sig_tvs
+ ; checkTc (null bad_tvs) (badPatSigTvs sig_ty bad_tvs)
+
-- Now match the pattern signature against res_ty
-- For convenience, and uniform-looking error messages
-- we do the matching by allocating meta type variables,
%************************************************************************
+%* *
+ Checking kinds
+%* *
+%************************************************************************
+
+We would like to get a decent error message from
+ (a) Under-applied type constructors
+ f :: (Maybe, Maybe)
+ (b) Over-applied type constructors
+ f :: Int x -> Int x
+
+\begin{code}
+-- The ExpKind datatype means "expected kind" and contains
+-- some info about just why that kind is expected, to improve
+-- the error message on a mis-match
+data ExpKind = EK TcKind EkCtxt
+data EkCtxt = EkUnk -- Unknown context
+ | EkEqPred -- Second argument of an equality predicate
+ | EkKindSig -- Kind signature
+ | EkArg SDoc Int -- Function, arg posn, expected kind
+
+
+ekLifted, ekOpen :: ExpKind
+ekLifted = EK liftedTypeKind EkUnk
+ekOpen = EK openTypeKind EkUnk
+
+checkExpectedKind :: Outputable a => a -> TcKind -> ExpKind -> TcM ()
+-- A fancy wrapper for 'unifyKind', which tries
+-- to give decent error messages.
+-- (checkExpectedKind ty act_kind exp_kind)
+-- checks that the actual kind act_kind is compatible
+-- with the expected kind exp_kind
+-- The first argument, ty, is used only in the error message generation
+checkExpectedKind ty act_kind (EK exp_kind ek_ctxt)
+ | act_kind `isSubKind` exp_kind -- Short cut for a very common case
+ = return ()
+ | otherwise = do
+ (_errs, mb_r) <- tryTc (unifyKind exp_kind act_kind)
+ case mb_r of
+ Just _ -> return () -- Unification succeeded
+ Nothing -> do
+
+ -- So there's definitely an error
+ -- Now to find out what sort
+ exp_kind <- zonkTcKind exp_kind
+ act_kind <- zonkTcKind act_kind
+
+ env0 <- tcInitTidyEnv
+ let (exp_as, _) = splitKindFunTys exp_kind
+ (act_as, _) = splitKindFunTys act_kind
+ n_exp_as = length exp_as
+ n_act_as = length act_as
+
+ (env1, tidy_exp_kind) = tidyKind env0 exp_kind
+ (env2, tidy_act_kind) = tidyKind env1 act_kind
+
+ err | n_exp_as < n_act_as -- E.g. [Maybe]
+ = quotes (ppr ty) <+> ptext (sLit "is not applied to enough type arguments")
+
+ -- Now n_exp_as >= n_act_as. In the next two cases,
+ -- n_exp_as == 0, and hence so is n_act_as
+ | isLiftedTypeKind exp_kind && isUnliftedTypeKind act_kind
+ = ptext (sLit "Expecting a lifted type, but") <+> quotes (ppr ty)
+ <+> ptext (sLit "is unlifted")
+
+ | isUnliftedTypeKind exp_kind && isLiftedTypeKind act_kind
+ = ptext (sLit "Expecting an unlifted type, but") <+> quotes (ppr ty)
+ <+> ptext (sLit "is lifted")
+
+ | otherwise -- E.g. Monad [Int]
+ = ptext (sLit "Kind mis-match")
+
+ more_info = sep [ expected_herald ek_ctxt <+> ptext (sLit "kind")
+ <+> quotes (pprKind tidy_exp_kind) <> comma,
+ ptext (sLit "but") <+> quotes (ppr ty) <+>
+ ptext (sLit "has kind") <+> quotes (pprKind tidy_act_kind)]
+
+ expected_herald EkUnk = ptext (sLit "Expected")
+ expected_herald EkKindSig = ptext (sLit "An enclosing kind signature specified")
+ expected_herald EkEqPred = ptext (sLit "The left argument of the equality predicate had")
+ expected_herald (EkArg fun arg_no)
+ = ptext (sLit "The") <+> speakNth arg_no <+> ptext (sLit "argument of")
+ <+> quotes fun <+> ptext (sLit ("should have"))
+
+ failWithTcM (env2, err $$ more_info)
+\end{code}
+
+%************************************************************************
%* *
Scoped type variables
%* *
\begin{code}
pprHsSigCtxt :: UserTypeCtxt -> LHsType Name -> SDoc
-pprHsSigCtxt ctxt hs_ty = vcat [ ptext (sLit "In") <+> pprUserTypeCtxt ctxt <> colon,
+pprHsSigCtxt ctxt hs_ty = sep [ ptext (sLit "In") <+> pprUserTypeCtxt ctxt <> colon,
nest 2 (pp_sig ctxt) ]
where
pp_sig (FunSigCtxt n) = pp_n_colon n
<+> pprQuotedList sig_tvs)
2 (ptext (sLit "unless the pattern has a rigid type context"))
+badPatSigTvs :: TcType -> [TyVar] -> SDoc
+badPatSigTvs sig_ty bad_tvs
+ = vcat [ fsep [ptext (sLit "The type variable") <> plural bad_tvs,
+ quotes (pprWithCommas ppr bad_tvs),
+ ptext (sLit "should be bound by the pattern signature") <+> quotes (ppr sig_ty),
+ ptext (sLit "but are actually discarded by a type synonym") ]
+ , ptext (sLit "To fix this, expand the type synonym")
+ , ptext (sLit "[Note: I hope to lift this restriction in due course]") ]
+
scopedNonVar :: Name -> Type -> SDoc
scopedNonVar n ty
= vcat [sep [ptext (sLit "The scoped type variable") <+> quotes (ppr n),
2 (vcat [ptext (sLit "are bound to the same type (variable)"),
ptext (sLit "Distinct scoped type variables must be distinct")])
-wrongEqualityErr :: TcM (HsType Name, TcKind)
-wrongEqualityErr
- = failWithTc (text "Equality predicate used as a type")
+wrongPredErr :: HsPred Name -> TcM (HsType Name, TcKind)
+wrongPredErr pred = failWithTc (text "Predicate used as a type:" <+> ppr pred)
\end{code}
projects / ghc-hetmet.git / blobdiff