From: simonpj@microsoft.com <unknown>
Date: Fri, 2 Oct 2009 11:15:49 +0000 (+0000)
Subject: Fix pretty-printing precedence for equality constraints
X-Git-Url: http://git.megacz.com/?p=ghc-hetmet.git;a=commitdiff_plain;h=24c13c1369c2ed21123c0c6eba7a7d7ab0313b86

Fix pretty-printing precedence for equality constraints
---

diff --git a/compiler/types/TypeRep.lhs b/compiler/types/TypeRep.lhs
index c3bd746..5c29087 100644
--- a/compiler/types/TypeRep.lhs
+++ b/compiler/types/TypeRep.lhs
@@ -431,7 +431,13 @@ pprTypeApp tc tys = ppr_type_app TopPrec (getName tc) tys
 pprPred :: PredType -> SDoc
 pprPred (ClassP cls tys) = pprClassPred cls tys
 pprPred (IParam ip ty)   = ppr ip <> dcolon <> pprType ty
-pprPred (EqPred ty1 ty2) = sep [ppr ty1, nest 2 (ptext (sLit "~")), ppr ty2]
+pprPred (EqPred ty1 ty2) = sep [ ppr_type FunPrec ty1
+                               , nest 2 (ptext (sLit "~"))
+                               , ppr_type FunPrec ty2]
+			       -- Precedence looks like (->) so that we get
+			       --    Maybe a ~ Bool
+			       --    (a->a) ~ Bool
+			       -- Note parens on the latter!
 
 pprClassPred :: Class -> [Type] -> SDoc
 pprClassPred clas tys = ppr_type_app TopPrec (getName clas) tys