[project @ 2004-11-11 08:58:23 by simonpj]

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

diff --git a/ghc/compiler/typecheck/TcMType.lhs b/ghc/compiler/typecheck/TcMType.lhs
index 45ab32e..09bbc26 100644 (file)
--- 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 
@@ -486,9 +486,6 @@ zonkType unbound_var_fn rflag ty
     go (TyConApp tycon tys)      = mappM go tys        `thenM` \ tys' ->
                                    returnM (TyConApp tycon tys')
 
-    go (NewTcApp tycon tys)      = mappM go tys        `thenM` \ tys' ->
-                                   returnM (NewTcApp tycon tys')
-
     go (NoteTy (SynNote ty1) ty2) = go ty1             `thenM` \ ty1' ->
                                    go ty2              `thenM` \ ty2' ->
                                    returnM (NoteTy (SynNote ty1') ty2')
@@ -525,9 +522,8 @@ zonkTyVar :: (TcTyVar -> TcM Type)          -- What to do for an unbound mutable variabl
           -> Bool                               -- Consult the type refinement?
          -> TcTyVar -> TcM TcType
 zonkTyVar unbound_var_fn rflag tyvar 
-  | not (isTcTyVar tyvar)      -- This can happen when
-                               -- zonking a forall type, when the bound type variable
-                               -- needn't be mutable
+  | not (isTcTyVar tyvar)      -- When zonking (forall a.  ...a...), the occurrences of 
+                               -- the quantified variable a are TyVars not TcTyVars
   = returnM (TyVarTy tyvar)
 
   | otherwise
@@ -765,9 +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_`
@@ -802,9 +806,6 @@ check_tau_type rank ubx_tup (NoteTy (SynNote syn) ty)
 check_tau_type rank ubx_tup (NoteTy other_note ty)
   = check_tau_type rank ubx_tup ty
 
-check_tau_type rank ubx_tup (NewTcApp tc tys)
-  = mappM_ check_arg_type tys
-
 check_tau_type rank ubx_tup ty@(TyConApp tc tys)
   | isSynTyCon tc      
   =    -- NB: Type.mkSynTy builds a TyConApp (not a NoteTy) for an unsaturated
@@ -838,7 +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