[project @ 2000-07-17 07:47:04 by simonpj]

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diff --git a/ghc/compiler/typecheck/TcTyDecls.lhs b/ghc/compiler/typecheck/TcTyDecls.lhs
index 226918e..acb1558 100644 (file)
--- a/ghc/compiler/typecheck/TcTyDecls.lhs
+++ b/ghc/compiler/typecheck/TcTyDecls.lhs
@@ -67,10 +67,18 @@ tcTyDecl1 (TySynonym tycon_name tyvar_names rhs src_loc)
   = tcLookupTy tycon_name                      `thenNF_Tc` \ (ATyCon tycon) ->
     tcExtendTyVarEnv (tyConTyVars tycon)       $
     tcHsType rhs                               `thenTc` \ rhs_ty ->
+       -- Note tcHsType not tcHsSigType; we allow type synonyms
+       -- that aren't types; e.g.  type List = []
+       --
        -- If the RHS mentions tyvars that aren't in scope, we'll 
-       -- quantify over them.  With gla-exts that's right, but for H98
-       -- we should complain. We can now do that here without falling into
+       -- quantify over them:
+       --      e.g.    type T = a->a
+       -- will become  type T = forall a. a->a
+       --
+       -- With gla-exts that's right, but for H98 we should complain. 
+       -- We can now do that here without falling into
        -- a black hole, we still do it in rnDecl (TySynonym case)
+
     returnTc (tycon_name, SynTyDetails rhs_ty)
 
 tcTyDecl1 (TyData _ context tycon_name _ con_decls _ derivings _  src_loc)