X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=ghc%2Fcompiler%2Ftypecheck%2FTcMType.lhs;h=09bbc26fbd3aeb721bbc7c946843b492072d6740;hb=8459e1aa09423e15bddccb97820bc1481c40a520;hp=570f2f566fd13fb23652dec75cf49e55505c8c85;hpb=32836fa7556e79a6f1f98c4019f7daf0400ad4fd;p=ghc-hetmet.git

diff --git a/ghc/compiler/typecheck/TcMType.lhs b/ghc/compiler/typecheck/TcMType.lhs
index 570f2f5..09bbc26 100644
--- a/ghc/compiler/typecheck/TcMType.lhs
+++ b/ghc/compiler/typecheck/TcMType.lhs
@@ -394,7 +394,7 @@ zonkTcPredType (IParam n t)
 \begin{code}
 zonkQuantifiedTyVar :: TcTyVar -> TcM TyVar
 -- zonkQuantifiedTyVar is applied to the a TcTyVar when quantifying over it.
--- It might be a meta TyVar, in which case we freeze it inot ano ordinary TyVar.
+-- It might be a meta TyVar, in which case we freeze it into an ordinary TyVar.
 -- When we do this, we also default the kind -- see notes with Kind.defaultKind
 -- The meta tyvar is updated to point to the new regular TyVar.  Now any 
 -- bound occurences of the original type variable will get zonked to 
@@ -761,9 +761,17 @@ check_tau_type :: Rank -> UbxTupFlag -> Type -> TcM ()
 -- Rank is allowed rank for function args
 -- No foralls otherwise
 
-check_tau_type rank ubx_tup ty@(ForAllTy _ _) = failWithTc (forAllTyErr ty)
-check_tau_type rank ubx_tup (PredTy sty)    = getDOpts		`thenM` \ dflags ->
-						check_source_ty dflags TypeCtxt sty
+check_tau_type rank ubx_tup ty@(ForAllTy _ _)       = failWithTc (forAllTyErr ty)
+check_tau_type rank ubx_tup ty@(FunTy (PredTy _) _) = failWithTc (forAllTyErr ty)
+	-- Reject e.g. (Maybe (?x::Int => Int)), with a decent error message
+
+-- Naked PredTys don't usually show up, but they can as a result of
+--	{-# SPECIALISE instance Ord Char #-}
+-- The Right Thing would be to fix the way that SPECIALISE instance pragmas
+-- are handled, but the quick thing is just to permit PredTys here.
+check_tau_type rank ubx_tup (PredTy sty) = getDOpts		`thenM` \ dflags ->
+					   check_source_ty dflags TypeCtxt sty
+
 check_tau_type rank ubx_tup (TyVarTy _)       = returnM ()
 check_tau_type rank ubx_tup ty@(FunTy arg_ty res_ty)
   = check_poly_type rank UT_NotOk arg_ty	`thenM_`
@@ -831,7 +839,7 @@ check_tau_type rank ubx_tup ty@(TyConApp tc tys)
     ubx_tup_msg = ubxArgTyErr ty
 
 ----------------------------------------
-forAllTyErr     ty = ptext SLIT("Illegal polymorphic type:") <+> ppr ty
+forAllTyErr     ty = ptext SLIT("Illegal polymorphic or qualified type:") <+> ppr ty
 unliftedArgErr  ty = ptext SLIT("Illegal unlifted type argument:") <+> ppr ty
 ubxArgTyErr     ty = ptext SLIT("Illegal unboxed tuple type as function argument:") <+> ppr ty
 kindErr kind       = ptext SLIT("Expecting an ordinary type, but found a type of kind") <+> ppr kind