From 1683eefd522552901d2b49b3c6619d07dcc5d467 Mon Sep 17 00:00:00 2001
From: simonpj <unknown>
Date: Mon, 17 Jul 2000 07:47:04 +0000
Subject: [PATCH] [project @ 2000-07-17 07:47:04 by simonpj] Add comments
---
ghc/compiler/typecheck/TcTyDecls.lhs | 12 ++++++++++--
1 file changed, 10 insertions(+), 2 deletions(-)
diff --git a/ghc/compiler/typecheck/TcTyDecls.lhs b/ghc/compiler/typecheck/TcTyDecls.lhs
index 226918e4bb2d..acb15586e8c6 100644
--- 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)
--
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