From: simonpj@microsoft.com <unknown>
Date: Wed, 14 Mar 2007 12:14:10 +0000 (+0000)
Subject: Improve typechecker error messages; see Trac #1221
X-Git-Url: http://git.megacz.com/?p=ghc-hetmet.git;a=commitdiff_plain;h=b03781ed8049e2037a5b573918d46dcdcd4baeb1

Improve typechecker error messages; see Trac #1221
---

diff --git a/compiler/typecheck/TcUnify.lhs b/compiler/typecheck/TcUnify.lhs
index 99cd7b9..8de9f6c 100644
--- a/compiler/typecheck/TcUnify.lhs
+++ b/compiler/typecheck/TcUnify.lhs
@@ -721,8 +721,12 @@ tc_sub1 sub_ctxt act_sty actual_ty exp_ib exp_sty expected_ty
 -----------------------------------
 defer_to_boxy_matching sub_ctxt act_sty actual_ty exp_ib exp_sty expected_ty
   = do	{ addSubCtxt sub_ctxt act_sty exp_sty $
-	  u_tys True False act_sty actual_ty exp_ib exp_sty expected_ty
+	  u_tys outer False act_sty actual_ty exp_ib exp_sty expected_ty
 	; return idHsWrapper }
+  where
+    outer = case sub_ctxt of		-- Ugh
+		SubDone -> False
+		other	-> True
 
 -----------------------------------
 tc_sub_funs act_arg act_res exp_ib exp_arg exp_res