diff options
| -rw-r--r-- | compiler/typecheck/TcUnify.lhs | 3 |
1 files changed, 2 insertions, 1 deletions
diff --git a/compiler/typecheck/TcUnify.lhs b/compiler/typecheck/TcUnify.lhs index 5fcaea6cf1..169cf7b5c4 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 } --------------- |