Treat the (~) type constructor a bit specially

[ghc-hetmet.git] / compiler / coreSyn / CoreLint.lhs

diff --git a/compiler/coreSyn/CoreLint.lhs b/compiler/coreSyn/CoreLint.lhs
index 031fd61..869f276 100644 (file)
--- a/compiler/coreSyn/CoreLint.lhs
+++ b/compiler/coreSyn/CoreLint.lhs
@@ -717,6 +717,8 @@ lintType ty@(FunTy t1 t2)
   = lint_ty_app ty (tyConKind funTyCon) [t1,t2]
 
 lintType ty@(TyConApp tc tys)
+  | tc `hasKey` eqPredPrimTyConKey     -- See Note [The (~) TyCon] in TysPrim
+  = lint_eq_pred ty tys
   | tyConHasKind tc
   = lint_ty_app ty (tyConKind tc) tys
   | otherwise
@@ -745,7 +747,18 @@ lint_ty_app :: Type -> Kind -> [OutType] -> LintM Kind
 lint_ty_app ty k tys 
   = do { ks <- mapM lintType tys
        ; lint_kind_app (ptext (sLit "type") <+> quotes (ppr ty)) k ks }
-                      
+
+lint_eq_pred :: Type -> [OutType] -> LintM Kind
+lint_eq_pred ty arg_tys
+  | [ty1,ty2] <- arg_tys
+  = do { k1 <- lintType ty1
+       ; k2 <- lintType ty2
+       ; checkL (k1 `eqKind` k2) 
+                (ptext (sLit "Mismatched arg kinds:") <+> ppr ty)
+       ; return unliftedTypeKind }
+  | otherwise
+  = failWithL (ptext (sLit "Unsaturated (~) type") <+> ppr ty)
+
 ----------------
 check_co_app :: Coercion -> Kind -> [OutType] -> LintM ()
 check_co_app ty k tys