From 536ef736dfc1568670d44072abfb4f16c84bcdb8 Mon Sep 17 00:00:00 2001
From: "simonpj@microsoft.com" <unknown>
Date: Mon, 11 Dec 2006 16:05:17 +0000
Subject: [PATCH] Suggests -fglasgow-exts for contexts-differ-in-length error

---
 compiler/typecheck/TcUnify.lhs |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/compiler/typecheck/TcUnify.lhs b/compiler/typecheck/TcUnify.lhs
index 5fcaea6..169cf7b 100644
--- a/compiler/typecheck/TcUnify.lhs
+++ b/compiler/typecheck/TcUnify.lhs
@@ -841,7 +841,8 @@ unifyTheta :: TcThetaType -> TcThetaType -> TcM ()
 -- Acutal and expected types
 unifyTheta theta1 theta2
   = do	{ checkTc (equalLength theta1 theta2)
-		  (ptext SLIT("Contexts differ in length"))
+		  (vcat [ptext SLIT("Contexts differ in length"),
+			 nest 2 $ parens $ ptext SLIT("Use -fglasgow-exts to allow this")])
 	; uList unifyPred theta1 theta2 }
 
 ---------------
-- 
1.7.10.4