Improve error message in TcHsType

[ghc-hetmet.git] / compiler / typecheck / TcHsType.lhs

diff --git a/compiler/typecheck/TcHsType.lhs b/compiler/typecheck/TcHsType.lhs
index e4b1267..31cf70e 100644 (file)
--- a/compiler/typecheck/TcHsType.lhs
+++ b/compiler/typecheck/TcHsType.lhs
@@ -191,8 +191,7 @@ kcHsSigType ty           = kcTypeType ty
 kcHsLiftedSigType 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.]
@@ -242,15 +241,23 @@ kcCheckHsType (L span ty) exp_kind
                -- because checkExpectedKind already mentions
                -- 'ty' by name in any error message
 
-       ; checkExpectedKind ty act_kind exp_kind
+       ; checkExpectedKind (strip ty) act_kind exp_kind
        ; return (L span 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
+       -- 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 _ []) (L _ ty)) thing = add_ctxt ty 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
@@ -561,8 +568,8 @@ tcLHsConResTy res_ty
     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 = get_args (HsTyVar tc) (ty1:ty2:args)
-    get_args ty                          args = (ty, reverse 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:"))
@@ -613,7 +620,7 @@ tcTyVarBndrs bndrs thing_inside
 
 -----------------------------------
 tcDataKindSig :: Maybe Kind -> TcM [TyVar]
--- GADT decls can have a (perhpas partial) kind signature
+-- 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 *