-
+%
+% (c) The University of Glasgow 2006
% (c) The GRASP/AQUA Project, Glasgow University, 1992-1998
%
\section[TcMonoType]{Typechecking user-specified @MonoTypes@}
\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, kcHsLPred, dsHsLPred,
+ tcDataKindSig, ExpKind(..), EkCtxt(..),
-- Pattern type signatures
tcHsPatSigType, tcPatSig
#include "HsVersions.h"
-import HsSyn ( HsType(..), LHsType, HsTyVarBndr(..), LHsTyVarBndr,
- LHsContext, HsPred(..), LHsPred, HsExplicitForAll(..) )
-import RnHsSyn ( extractHsTyVars )
+#ifdef GHCI /* Only if bootstrapped */
+import {-# SOURCE #-} TcSplice( kcSpliceType )
+#endif
+
+import HsSyn
+import RnHsSyn
import TcRnMonad
-import TcEnv ( tcExtendTyVarEnv, tcExtendKindEnvTvs,
- tcLookup, tcLookupClass, tcLookupTyCon,
- TyThing(..), getInLocalScope, getScopedTyVarBinds,
- wrongThingErr
- )
-import TcMType ( newKindVar,
- zonkTcKindToKind,
- tcInstBoxyTyVar, readFilledBox,
- checkValidType
- )
-import TcUnify ( boxyUnify, unifyFunKind, checkExpectedKind )
-import TcIface ( checkWiredInTyCon )
-import TcType ( Type, PredType(..), ThetaType, BoxySigmaType,
- TcType, TcKind, isRigidTy,
- UserTypeCtxt(..), pprUserTypeCtxt,
- substTyWith, mkTyVarTys, tcEqType,
- tcIsTyVarTy, mkFunTy, mkSigmaTy, mkPredTy,
- mkTyConApp, mkAppTys, typeKind )
-import Kind ( Kind, isLiftedTypeKind, liftedTypeKind, ubxTupleKind,
- openTypeKind, argTypeKind, splitKindFunTys )
-import Var ( TyVar, mkTyVar, tyVarName )
-import TyCon ( TyCon, tyConKind )
-import Class ( Class, classTyCon )
-import Name ( Name, mkInternalName )
-import OccName ( mkOccName, tvName )
+import TcEnv
+import TcMType
+import TcUnify
+import TcIface
+import TcType
+import TypeRep ( ecKind )
+import {- Kind parts of -} Type
+import Var
+import VarSet
+import TyCon
+import Class
+import Name
import NameSet
-import PrelNames ( genUnitTyConName )
-import TysWiredIn ( mkListTy, listTyCon, mkPArrTy, parrTyCon, tupleTyCon )
-import BasicTypes ( Boxity(..) )
-import SrcLoc ( Located(..), unLoc, noLoc, getLoc, srcSpanStart )
-import UniqSupply ( uniqsFromSupply )
+import TysWiredIn
+import BasicTypes
+import SrcLoc
+import Util
+import UniqSupply
import Outputable
+import FastString
\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
- ; returnM ty }
+ ; return ty }
+
+tcHsInstHead :: LHsType Name -> TcM ([TyVar], ThetaType, Class, [Type])
+-- Typecheck an instance head. We can't use
+-- tcHsSigType, because it's not a valid user type.
+tcHsInstHead (L loc hs_ty)
+ = setSrcSpan loc $ -- No need for an "In the type..." context
+ -- because that comes from the caller
+ do { kinded_ty <- kc_inst_head hs_ty
+ ; ds_inst_head kinded_ty }
+ where
+ kc_inst_head ty@(HsPredTy pred@(HsClassP {}))
+ = do { (pred', kind) <- kc_pred pred
+ ; checkExpectedKind ty kind ekLifted
+ ; return (HsPredTy pred') }
+ kc_inst_head (HsForAllTy exp tv_names context (L loc ty))
+ = kcHsTyVars tv_names $ \ tv_names' ->
+ do { ctxt' <- kcHsContext context
+ ; ty' <- kc_inst_head ty
+ ; return (HsForAllTy exp tv_names' ctxt' (L loc ty')) }
+ kc_inst_head _ = failWithTc (ptext (sLit "Malformed instance type"))
+
+ ds_inst_head (HsPredTy (HsClassP cls_name tys))
+ = do { clas <- tcLookupClass cls_name
+ ; arg_tys <- dsHsTypes tys
+ ; return ([], [], clas, arg_tys) }
+ ds_inst_head (HsForAllTy _ tvs ctxt (L _ tau))
+ = tcTyVarBndrs tvs $ \ tvs' ->
+ do { ctxt' <- mapM dsHsLPred (unLoc ctxt)
+ ; (tvs_r, ctxt_r, cls, tys) <- ds_inst_head tau
+ ; return (tvs' ++ tvs_r, ctxt' ++ ctxt_r , cls, tys) }
+ ds_inst_head _ = panic "ds_inst_head"
+
+tcHsQuantifiedType :: [LHsTyVarBndr Name] -> LHsType Name -> TcM ([TyVar], Type)
+-- Behave very like type-checking (HsForAllTy sig_tvs hs_ty),
+-- except that we want to keep the tvs separate
+tcHsQuantifiedType tv_names hs_ty
+ = kcHsTyVars tv_names $ \ tv_names' ->
+ do { kc_ty <- kcHsSigType hs_ty
+ ; tcTyVarBndrs tv_names' $ \ tvs ->
+ do { ty <- dsHsType kc_ty
+ ; return (tvs, ty) } }
-- Used for the deriving(...) items
-tcHsDeriv :: LHsType Name -> TcM ([TyVar], Class, [Type])
-tcHsDeriv = addLocM (tc_hs_deriv [])
+tcHsDeriv :: HsType Name -> TcM ([TyVar], Class, [Type])
+tcHsDeriv = tc_hs_deriv []
+tc_hs_deriv :: [LHsTyVarBndr Name] -> HsType Name
+ -> TcM ([TyVar], Class, [Type])
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
tc_hs_deriv (tv_names1 ++ tv_names2) ty
tc_hs_deriv _ other
- = failWithTc (ptext SLIT("Illegal deriving item") <+> ppr other)
+ = failWithTc (ptext (sLit "Illegal deriving item") <+> ppr other)
\end{code}
These functions are used during knot-tying in
\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,
- -- but do hoist for-alls to the top
+ -- Don't do kind checking, nor validity checking.
-- This is used in type and class decls, where kinding is
-- done in advance, and validity checking is done later
-- [Validity checking done later because of knot-tying issues.]
tcHsBangType :: LHsType Name -> TcM Type
-- Permit a bang, but discard it
-tcHsBangType (L span (HsBangTy b ty)) = tcHsKindedType ty
-tcHsBangType ty = tcHsKindedType ty
+tcHsBangType (L _ (HsBangTy _ ty)) = tcHsKindedType ty
+tcHsBangType ty = tcHsKindedType ty
tcHsKindedContext :: LHsContext Name -> TcM ThetaType
-- Used when we are expecting a ClassContext (i.e. no implicit params)
-- Does not do validity checking, like tcHsKindedType
-tcHsKindedContext hs_theta = addLocM (mappM dsHsLPred) hs_theta
+tcHsKindedContext hs_theta = addLocM (mapM dsHsLPred) hs_theta
\end{code}
---------------------------
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 ty act_kind exp_kind
- ; return (L span ty') }
+ ; checkExpectedKind (strip ty) act_kind exp_kind
+ ; return ty' }
where
- -- Wrap a context around only if we want to
- -- show that contexts. Omit invisble ones
- -- and ones user's won't grok (HsPred p).
- add_ctxt (HsPredTy p) thing = thing
- add_ctxt (HsForAllTy Implicit tvs (L _ []) ty) thing = thing
- add_ctxt other_ty thing = addErrCtxt (typeCtxt 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
+ -- when the real difficulty is with the 'ty' part.
+ strip (HsParTy (L _ ty)) = strip ty
+ strip (HsBangTy _ (L _ ty)) = strip ty
+ strip (HsForAllTy _ _ _ (L _ ty)) = strip ty
+ strip ty = ty
\end{code}
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
--
-- The translated type has explicitly-kinded type-variable binders
-kc_hs_type (HsParTy ty)
- = kcHsType ty `thenM` \ (ty', kind) ->
- returnM (HsParTy ty', kind)
-
-kc_hs_type (HsTyVar name)
- = kcTyVar name `thenM` \ kind ->
- returnM (HsTyVar name, kind)
-
-kc_hs_type (HsListTy ty)
- = kcLiftedType ty `thenM` \ ty' ->
- returnM (HsListTy ty', liftedTypeKind)
-
-kc_hs_type (HsPArrTy ty)
- = kcLiftedType ty `thenM` \ ty' ->
- returnM (HsPArrTy ty', liftedTypeKind)
-
-kc_hs_type (HsNumTy n)
- = returnM (HsNumTy n, liftedTypeKind)
-
-kc_hs_type (HsKindSig ty k)
- = kcCheckHsType ty k `thenM` \ ty' ->
- returnM (HsKindSig ty' k, k)
-
-kc_hs_type (HsTupleTy Boxed tys)
- = mappM kcLiftedType tys `thenM` \ tys' ->
- returnM (HsTupleTy Boxed tys', liftedTypeKind)
-
-kc_hs_type (HsTupleTy Unboxed tys)
- = mappM kcTypeType tys `thenM` \ tys' ->
- returnM (HsTupleTy Unboxed tys', ubxTupleKind)
-
-kc_hs_type (HsFunTy ty1 ty2)
- = kcCheckHsType ty1 argTypeKind `thenM` \ ty1' ->
- kcTypeType ty2 `thenM` \ ty2' ->
- returnM (HsFunTy ty1' ty2', liftedTypeKind)
-
-kc_hs_type ty@(HsOpTy ty1 op ty2)
- = addLocM kcTyVar op `thenM` \ op_kind ->
- kcApps op_kind (ppr op) [ty1,ty2] `thenM` \ ([ty1',ty2'], res_kind) ->
- returnM (HsOpTy ty1' op ty2', res_kind)
-
-kc_hs_type ty@(HsAppTy ty1 ty2)
- = kcHsType fun_ty `thenM` \ (fun_ty', fun_kind) ->
- kcApps fun_kind (ppr fun_ty) arg_tys `thenM` \ ((arg_ty':arg_tys'), res_kind) ->
- returnM (foldl mk_app (HsAppTy fun_ty' arg_ty') arg_tys', res_kind)
+kc_hs_type :: HsType Name -> TcM (HsType Name, TcKind)
+kc_hs_type (HsParTy ty) = do
+ (ty', kind) <- kc_lhs_type ty
+ return (HsParTy ty', kind)
+
+kc_hs_type (HsTyVar name) = do
+ kind <- kcTyVar name
+ return (HsTyVar name, kind)
+
+kc_hs_type (HsListTy ty) = do
+ ty' <- kcLiftedType ty
+ return (HsListTy ty', liftedTypeKind)
+
+kc_hs_type (HsPArrTy ty) = do
+ ty' <- kcLiftedType ty
+ return (HsPArrTy ty', liftedTypeKind)
+
+kc_hs_type (HsModalBoxType ecn ty) = do
+ kc_check_hs_type (HsTyVar ecn) (EK ecKind EkUnk)
+ ty' <- kcLiftedType ty
+ return (HsModalBoxType ecn ty', liftedTypeKind)
+
+kc_hs_type (HsKindSig ty k) = do
+ ty' <- kc_check_lhs_type ty (EK k EkKindSig)
+ return (HsKindSig ty' k, k)
+
+kc_hs_type (HsTupleTy Boxed tys) = do
+ tys' <- mapM kcLiftedType tys
+ return (HsTupleTy Boxed tys', liftedTypeKind)
+
+kc_hs_type (HsTupleTy Unboxed tys) = do
+ tys' <- mapM kcTypeType tys
+ return (HsTupleTy Unboxed tys', ubxTupleKind)
+
+kc_hs_type (HsFunTy ty1 ty2) = do
+ 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 op_kind [ty1,ty2]
+ return (HsOpTy ty1' op ty2', res_kind)
+
+kc_hs_type (HsAppTy ty1 ty2) = do
+ (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 pred)
- = kcHsPred pred `thenM` \ pred' ->
- returnM (HsPredTy pred', liftedTypeKind)
+ = wrongPredErr pred
+
+kc_hs_type (HsCoreTy ty)
+ = return (HsCoreTy ty, typeKind ty)
kc_hs_type (HsForAllTy exp tv_names context ty)
- = kcHsTyVars tv_names $ \ tv_names' ->
- kcHsContext context `thenM` \ ctxt' ->
- kcLiftedType ty `thenM` \ ty' ->
- -- The body of a forall is usually a type, but in principle
- -- there's no reason to prohibit *unlifted* types.
- -- In fact, GHC can itself construct a function with an
- -- unboxed tuple inside a for-all (via CPR analyis; see
- -- typecheck/should_compile/tc170)
- --
- -- Still, that's only for internal interfaces, which aren't
- -- kind-checked, so we only allow liftedTypeKind here
- returnM (HsForAllTy exp tv_names' ctxt' ty', liftedTypeKind)
+ = kcHsTyVars tv_names $ \ tv_names' ->
+ do { ctxt' <- kcHsContext context
+ ; ty' <- kcLiftedType ty
+ -- The body of a forall is usually a type, but in principle
+ -- there's no reason to prohibit *unlifted* types.
+ -- In fact, GHC can itself construct a function with an
+ -- unboxed tuple inside a for-all (via CPR analyis; see
+ -- typecheck/should_compile/tc170)
+ --
+ -- Still, that's only for internal interfaces, which aren't
+ -- kind-checked, so we only allow liftedTypeKind here
+
+ ; return (HsForAllTy exp tv_names' ctxt' ty', liftedTypeKind) }
kc_hs_type (HsBangTy b ty)
- = do { (ty', kind) <- kcHsType 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 (HsDocTy ty _)
+ = 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
- = split_fk fun_kind (length args) `thenM` \ (arg_kinds, res_kind) ->
- zipWithM kc_arg args arg_kinds `thenM` \ args' ->
- returnM (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 = returnM ([], fk)
- split_fk fk n = unifyFunKind fk `thenM` \ mb_fk ->
- case mb_fk of
- Nothing -> failWithTc too_many_args
- Just (ak,fk') -> split_fk fk' (n-1) `thenM` \ (aks, rk) ->
- returnM (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 <+>
- ptext SLIT("is applied to too many type arguments")
+---------------------------
+splitFunKind :: SDoc -> Int -> TcKind -> [b] -> TcM ([(b,ExpKind)], TcKind)
+splitFunKind _ _ fk [] = return ([], fk)
+splitFunKind the_fun arg_no fk (arg:args)
+ = do { mb_fk <- matchExpectedFunKind 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")
---------------------------
kcHsContext :: LHsContext Name -> TcM (LHsContext Name)
-kcHsContext ctxt = wrapLocM (mappM kcHsLPred) ctxt
+kcHsContext ctxt = wrapLocM (mapM kcHsLPred) ctxt
kcHsLPred :: LHsPred Name -> TcM (LHsPred Name)
kcHsLPred = wrapLocM kcHsPred
kcHsPred :: HsPred Name -> TcM (HsPred Name)
-kcHsPred pred -- Checks that the result is of kind liftedType
- = kc_pred pred `thenM` \ (pred', kind) ->
- checkExpectedKind pred kind liftedTypeKind `thenM_`
- returnM pred'
+kcHsPred pred = do -- Checks that the result is a type kind
+ (pred', kind) <- kc_pred pred
+ checkExpectedKind pred kind ekOpen
+ return pred'
---------------------------
kc_pred :: HsPred Name -> TcM (HsPred Name, TcKind)
-- Does *not* check for a saturated
-- application (reason: used from TcDeriv)
-kc_pred pred@(HsIParam name ty)
- = kcHsType ty `thenM` \ (ty', kind) ->
- returnM (HsIParam name ty', kind)
-
-kc_pred pred@(HsClassP cls tys)
- = kcClass cls `thenM` \ kind ->
- kcApps kind (ppr cls) tys `thenM` \ (tys', res_kind) ->
- returnM (HsClassP cls tys', res_kind)
+kc_pred (HsIParam name 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 cls kind tys
+ ; return (HsClassP cls tys', res_kind) }
+kc_pred (HsEqualP ty1 ty2)
+ = do { (ty1', kind1) <- kc_lhs_type ty1
+ ; (ty2', kind2) <- kc_lhs_type ty2
+ ; checkExpectedKind ty2 kind2 (EK kind1 EkEqPred)
+ ; return (HsEqualP ty1' ty2', unliftedTypeKind) }
---------------------------
kcTyVar :: Name -> TcM TcKind
-kcTyVar name -- Could be a tyvar or a tycon
- = traceTc (text "lk1" <+> ppr name) `thenM_`
- tcLookup name `thenM` \ thing ->
- traceTc (text "lk2" <+> ppr name <+> ppr thing) `thenM_`
+kcTyVar name = do -- Could be a tyvar or a tycon
+ traceTc "lk1" (ppr name)
+ thing <- tcLookup name
+ traceTc "lk2" (ppr name <+> ppr thing)
case thing of
- ATyVar _ ty -> returnM (typeKind ty)
- AThing kind -> returnM kind
- AGlobal (ATyCon tc) -> returnM (tyConKind tc)
- other -> wrongThingErr "type" thing name
+ ATyVar _ ty -> return (typeKind ty)
+ AThing kind -> return kind
+ AGlobal (ATyCon tc) -> return (tyConKind tc)
+ _ -> wrongThingErr "type" thing name
kcClass :: Name -> TcM TcKind
-kcClass cls -- Must be a class
- = tcLookup cls `thenM` \ thing ->
+kcClass cls = do -- Must be a class
+ thing <- tcLookup cls
case thing of
- AThing kind -> returnM kind
- AGlobal (AClass cls) -> returnM (tyConKind (classTyCon cls))
- other -> wrongThingErr "class" thing cls
+ AThing kind -> return kind
+ AGlobal (AClass cls) -> return (tyConKind (classTyCon cls))
+ _ -> wrongThingErr "class" thing cls
\end{code}
-- All HsTyVarBndrs in the intput type are kind-annotated
dsHsType ty = ds_type (unLoc ty)
-ds_type ty@(HsTyVar name)
+ds_type :: HsType Name -> TcM Type
+ds_type ty@(HsTyVar _)
= ds_app ty []
ds_type (HsParTy ty) -- Remove the parentheses markers
= dsHsType ty
-ds_type ty@(HsBangTy _ _) -- No bangs should be here
- = failWithTc (ptext SLIT("Unexpected strictness annotation:") <+> ppr ty)
-
-ds_type (HsKindSig ty k)
- = dsHsType ty -- Kind checking done already
+ds_type ty@(HsBangTy {}) -- No bangs should be here
+ = failWithTc (ptext (sLit "Unexpected strictness annotation:") <+> ppr ty)
-ds_type (HsListTy ty)
- = dsHsType ty `thenM` \ tau_ty ->
- checkWiredInTyCon listTyCon `thenM_`
- returnM (mkListTy tau_ty)
+ds_type ty@(HsRecTy {}) -- No bangs should be here
+ = failWithTc (ptext (sLit "Unexpected record type:") <+> ppr ty)
-ds_type (HsPArrTy ty)
- = dsHsType ty `thenM` \ tau_ty ->
- checkWiredInTyCon parrTyCon `thenM_`
- returnM (mkPArrTy tau_ty)
+ds_type (HsKindSig ty _)
+ = dsHsType ty -- Kind checking done already
-ds_type (HsTupleTy boxity tys)
- = dsHsTypes tys `thenM` \ tau_tys ->
- checkWiredInTyCon tycon `thenM_`
- returnM (mkTyConApp tycon tau_tys)
+ds_type (HsListTy ty) = do
+ tau_ty <- dsHsType ty
+ checkWiredInTyCon listTyCon
+ return (mkListTy tau_ty)
+
+ds_type (HsPArrTy ty) = do
+ tau_ty <- dsHsType ty
+ checkWiredInTyCon parrTyCon
+ return (mkPArrTy tau_ty)
+
+ds_type (HsModalBoxType ecn ty) = do
+ tau_ty <- dsHsType ty
+ checkWiredInTyCon hetMetCodeTypeTyCon
+ return (mkHetMetCodeTypeTy (mkTyVar ecn ecKind) tau_ty)
+
+ds_type (HsTupleTy boxity tys) = do
+ tau_tys <- dsHsTypes tys
+ checkWiredInTyCon tycon
+ return (mkTyConApp tycon tau_tys)
where
tycon = tupleTyCon boxity (length tys)
-ds_type (HsFunTy ty1 ty2)
- = dsHsType ty1 `thenM` \ tau_ty1 ->
- dsHsType ty2 `thenM` \ tau_ty2 ->
- returnM (mkFunTy tau_ty1 tau_ty2)
+ds_type (HsFunTy ty1 ty2) = do
+ tau_ty1 <- dsHsType ty1
+ tau_ty2 <- dsHsType ty2
+ return (mkFunTy tau_ty1 tau_ty2)
-ds_type (HsOpTy ty1 (L span op) ty2)
- = dsHsType ty1 `thenM` \ tau_ty1 ->
- dsHsType ty2 `thenM` \ tau_ty2 ->
+ds_type (HsOpTy ty1 (L span op) ty2) = do
+ tau_ty1 <- dsHsType ty1
+ tau_ty2 <- dsHsType ty2
setSrcSpan span (ds_var_app op [tau_ty1,tau_ty2])
-ds_type (HsNumTy n)
- = ASSERT(n==1)
- tcLookupTyCon genUnitTyConName `thenM` \ tc ->
- returnM (mkTyConApp tc [])
-
ds_type ty@(HsAppTy _ _)
= ds_app ty []
-ds_type (HsPredTy pred)
- = dsHsPred pred `thenM` \ pred' ->
- returnM (mkPredTy pred')
+ds_type (HsPredTy pred) = do
+ pred' <- dsHsPred pred
+ return (mkPredTy pred')
+
+ds_type (HsForAllTy _ tv_names ctxt ty)
+ = tcTyVarBndrs tv_names $ \ tyvars -> do
+ theta <- mapM dsHsLPred (unLoc ctxt)
+ tau <- dsHsType ty
+ return (mkSigmaTy tyvars theta tau)
-ds_type full_ty@(HsForAllTy exp tv_names ctxt ty)
- = tcTyVarBndrs tv_names $ \ tyvars ->
- mappM dsHsLPred (unLoc ctxt) `thenM` \ theta ->
- dsHsType ty `thenM` \ tau ->
- returnM (mkSigmaTy tyvars theta tau)
+ds_type (HsDocTy ty _) -- Remove the doc comment
+ = dsHsType ty
+
+ds_type (HsSpliceTy _ _ kind)
+ = do { kind' <- zonkTcKindToKind kind
+ ; newFlexiTyVarTy kind' }
-dsHsTypes arg_tys = mappM dsHsType arg_tys
+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}
Help functions for type applications
ds_app (HsAppTy ty1 ty2) tys
= ds_app (unLoc ty1) (ty2:tys)
-ds_app ty tys
- = dsHsTypes tys `thenM` \ arg_tys ->
+ds_app ty tys = do
+ arg_tys <- dsHsTypes tys
case ty of
HsTyVar fun -> ds_var_app fun arg_tys
- other -> ds_type ty `thenM` \ fun_ty ->
- returnM (mkAppTys fun_ty arg_tys)
+ _ -> do fun_ty <- ds_type ty
+ return (mkAppTys fun_ty arg_tys)
ds_var_app :: Name -> [Type] -> TcM Type
-ds_var_app name arg_tys
- = tcLookup name `thenM` \ thing ->
+ds_var_app name arg_tys = do
+ thing <- tcLookup name
case thing of
- ATyVar _ ty -> returnM (mkAppTys ty arg_tys)
- AGlobal (ATyCon tc) -> returnM (mkTyConApp tc arg_tys)
- other -> wrongThingErr "type" thing name
+ ATyVar _ ty -> return (mkAppTys ty arg_tys)
+ AGlobal (ATyCon tc) -> return (mkTyConApp tc arg_tys)
+ _ -> wrongThingErr "type" thing name
\end{code}
dsHsLPred :: LHsPred Name -> TcM PredType
dsHsLPred pred = dsHsPred (unLoc pred)
-dsHsPred pred@(HsClassP class_name tys)
- = dsHsTypes tys `thenM` \ arg_tys ->
- tcLookupClass class_name `thenM` \ clas ->
- returnM (ClassP clas arg_tys)
-
+dsHsPred :: HsPred Name -> TcM PredType
+dsHsPred (HsClassP class_name tys)
+ = do { arg_tys <- dsHsTypes tys
+ ; clas <- tcLookupClass class_name
+ ; return (ClassP clas arg_tys)
+ }
+dsHsPred (HsEqualP ty1 ty2)
+ = do { arg_ty1 <- dsHsType ty1
+ ; arg_ty2 <- dsHsType ty2
+ ; return (EqPred arg_ty1 arg_ty2)
+ }
dsHsPred (HsIParam name ty)
- = dsHsType ty `thenM` \ arg_ty ->
- returnM (IParam name arg_ty)
+ = do { arg_ty <- dsHsType ty
+ ; return (IParam name arg_ty)
+ }
\end{code}
-GADT constructor signatures
-
\begin{code}
-tcLHsConResTy :: LHsType Name -> TcM (TyCon, [TcType])
-tcLHsConResTy res_ty
- = addErrCtxt (gadtResCtxt res_ty) $
- case get_largs 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')
- other -> failWithTc (badGadtDecl res_ty) }
- other -> 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_largs (L _ ty) args = get_args ty args
- get_args (HsAppTy fun arg) args = get_largs fun (arg:args)
- get_args (HsParTy ty) args = get_largs ty args
- get_args (HsOpTy ty1 (L span tc) ty2) args = (HsTyVar tc, ty1:ty2:args)
- get_args ty args = (ty, args)
-
-gadtResCtxt ty
- = hang (ptext SLIT("In the result type of a data constructor:"))
- 2 (ppr ty)
-badGadtDecl ty
- = hang (ptext SLIT("Malformed constructor result type:"))
- 2 (ppr ty)
-
-typeCtxt ty = ptext SLIT("In the type") <+> quotes (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)
\end{code}
%************************************************************************
-> ([LHsTyVarBndr Name] -> TcM r) -- These binders are kind-annotated
-- They scope over the thing inside
-> TcM r
-kcHsTyVars tvs thing_inside
- = mappM (wrapLocM kcHsTyVar) tvs `thenM` \ bndrs ->
- 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) = newKindVar `thenM` \ kind ->
- returnM (KindedTyVar name kind)
-kcHsTyVar (KindedTyVar name kind) = returnM (KindedTyVar name kind)
+kcHsTyVar (UserTyVar name _) = UserTyVar name <$> newKindVar
+kcHsTyVar tv@(KindedTyVar {}) = return tv
------------------
tcTyVarBndrs :: [LHsTyVarBndr Name] -- Kind-annotated binders, which need kind-zonking
-> TcM r
-- Used when type-checking types/classes/type-decls
-- Brings into scope immutable TyVars, not mutable ones that require later zonking
-tcTyVarBndrs bndrs thing_inside
- = mapM (zonk . unLoc) bndrs `thenM` \ tyvars ->
+tcTyVarBndrs bndrs thing_inside = do
+ 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) = pprTrace "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]
-- GADT decls can have a (perhaps partial) kind signature
-- e.g. data T :: * -> * -> * where ...
-- This function makes up suitable (kinded) type variables for
--- the argument kinds, and checks that the result kind is indeed *
+-- the argument kinds, and checks that the result kind is indeed *.
+-- We use it also to make up argument type variables for for data instances.
tcDataKindSig Nothing = return []
tcDataKindSig (Just kind)
= do { checkTc (isLiftedTypeKind res_kind) (badKindSig kind)
; span <- getSrcSpanM
; us <- newUniqueSupply
- ; let loc = srcSpanStart span
- uniqs = uniqsFromSupply us
- ; return [ mk_tv loc uniq str kind
- | ((kind, str), uniq) <- arg_kinds `zip` names `zip` uniqs ] }
+ ; let uniqs = uniqsFromSupply us
+ ; return [ mk_tv span uniq str kind
+ | ((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
badKindSig kind
- = hang (ptext SLIT("Kind signature on data type declaration has non-* return kind"))
+ = hang (ptext (sLit "Kind signature on data type declaration has non-* return kind"))
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) ]
-
- -- Behave very like type-checking (HsForAllTy sig_tvs hs_ty),
- -- except that we want to keep the tvs separate
- ; (kinded_tvs, kinded_ty) <- kcHsTyVars sig_tvs $ \ kinded_tvs -> do
- { kinded_ty <- kcTypeType hs_ty
- ; return (kinded_tvs, kinded_ty) }
- ; tcTyVarBndrs kinded_tvs $ \ tyvars -> do
- { sig_ty <- dsHsType kinded_ty
+ 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
; return (tyvars, sig_ty)
- } }
+ }
tcPatSig :: UserTypeCtxt
-> LHsType Name
- -> BoxySigmaType
+ -> TcSigmaType
-> TcM (TcType, -- The type to use for "inside" the signature
- [(Name,TcType)]) -- The new bit of type environment, binding
+ [(Name, TcType)], -- The new bit of type environment, binding
-- the scoped type variables
+ HsWrapper) -- Coercion due to unification with actual ty
+ -- Of shape: res_ty ~ sig_ty
tcPatSig ctxt sig res_ty
= do { (sig_tvs, sig_ty) <- tcHsPatSigType ctxt sig
+ -- sig_tvs are the type variables free in 'sig',
+ -- and not already in scope. These are the ones
+ -- that should be brought into scope
; if null sig_tvs then do {
-- The type signature binds no type variables,
-- and hence is rigid, so use it to zap the res_ty
- boxyUnify sig_ty res_ty
- ; return (sig_ty, [])
-
- } else do {
+ wrap <- tcSubType PatSigOrigin ctxt res_ty sig_ty
+ ; return (sig_ty, [], wrap)
+ } else do {
-- Type signature binds at least one scoped type variable
-- A pattern binding cannot bind scoped type variables
-- So we just have an ASSERT here
; let in_pat_bind = case ctxt of
BindPatSigCtxt -> True
- other -> False
+ _ -> False
; ASSERT( not in_pat_bind || null sig_tvs ) return ()
- -- Check that pat_ty is rigid
- ; checkTc (isRigidTy res_ty) (wobblyPatSig sig_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,
- -- unifying, and reading out the results.
- -- This is a strictly local operation.
- ; box_tvs <- mapM tcInstBoxyTyVar sig_tvs
- ; boxyUnify (substTyWith sig_tvs (mkTyVarTys box_tvs) sig_ty) res_ty
- ; sig_tv_tys <- mapM readFilledBox box_tvs
-
- -- Check that each is bound to a distinct type variable,
- -- and one that is not already in scope
- ; let tv_binds = map tyVarName sig_tvs `zip` sig_tv_tys
- ; binds_in_scope <- getScopedTyVarBinds
+ -- 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 do a subsumption check of the pattern signature against res_ty
+ ; sig_tvs' <- tcInstSigTyVars sig_tvs
+ ; let sig_ty' = substTyWith sig_tvs sig_tv_tys' sig_ty
+ sig_tv_tys' = mkTyVarTys sig_tvs'
+ ; wrap <- tcSubType PatSigOrigin ctxt res_ty sig_ty'
+
+ -- Check that each is bound to a distinct type variable,
+ -- and one that is not already in scope
+ ; binds_in_scope <- getScopedTyVarBinds
+ ; let tv_binds = map tyVarName sig_tvs `zip` sig_tv_tys'
; check binds_in_scope tv_binds
- -- Phew!
- ; return (res_ty, tv_binds)
- } }
+ -- Phew!
+ ; return (sig_ty', tv_binds, wrap)
+ } }
where
- check in_scope [] = return ()
+ check _ [] = return ()
check in_scope ((n,ty):rest) = do { check_one in_scope n ty
; check ((n,ty):in_scope) rest }
check_one in_scope n ty
- = do { checkTc (tcIsTyVarTy ty) (scopedNonVar n ty)
- -- Must bind to a type variable
-
- ; checkTc (null dups) (dupInScope n (head dups) ty)
+ = checkTc (null dups) (dupInScope n (head dups) ty)
-- Must not bind to the same type variable
-- as some other in-scope type variable
-
- ; return () }
where
- dups = [n' | (n',ty') <- in_scope, tcEqType ty' ty]
+ dups = [n' | (n',ty') <- in_scope, eqType ty' ty]
\end{code}
%************************************************************************
+%* *
+ 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
pp_sig (ConArgCtxt n) = pp_n_colon n
pp_sig (ForSigCtxt n) = pp_n_colon n
- pp_sig (RuleSigCtxt n) = pp_n_colon n
- pp_sig other = ppr (unLoc hs_ty)
+ pp_sig _ = ppr (unLoc hs_ty)
pp_n_colon n = ppr n <+> dcolon <+> ppr (unLoc hs_ty)
-
-wobblyPatSig sig_tvs
- = hang (ptext SLIT("A pattern type signature cannot bind scoped type variables")
- <+> pprQuotedList sig_tvs)
- 2 (ptext SLIT("unless the pattern has a rigid type context"))
-
-scopedNonVar n ty
- = vcat [sep [ptext SLIT("The scoped type variable") <+> quotes (ppr n),
- nest 2 (ptext SLIT("is bound to the type") <+> quotes (ppr ty))],
- nest 2 (ptext SLIT("You can only bind scoped type variables to type variables"))]
-
-dupInScope n n' ty
- = hang (ptext SLIT("The scoped type variables") <+> quotes (ppr n) <+> ptext SLIT("and") <+> quotes (ppr n'))
- 2 (vcat [ptext SLIT("are bound to the same type (variable)"),
- ptext SLIT("Distinct scoped type variables must be distinct")])
+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]") ]
+
+dupInScope :: Name -> Name -> Type -> SDoc
+dupInScope n n' _
+ = hang (ptext (sLit "The scoped type variables") <+> quotes (ppr n) <+> ptext (sLit "and") <+> quotes (ppr n'))
+ 2 (vcat [ptext (sLit "are bound to the same type (variable)"),
+ ptext (sLit "Distinct scoped type variables must be distinct")])
+
+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