X-Git-Url: http://git.megacz.com/?p=ghc-hetmet.git;a=blobdiff_plain;f=compiler%2Ftypecheck%2FTcUnify.lhs;h=169cf7b5c46b5d78dbf1f41b1d8267353d90971f;hp=5fcaea6cf1bc25d61f67f2ea3c50d3096a72ee25;hb=536ef736dfc1568670d44072abfb4f16c84bcdb8;hpb=4e5faff9152918cd00dcdad9068b0f1eba1fcd68

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 }
 
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