From: simonpj@microsoft.com <unknown>
Date: Thu, 27 Jul 2006 15:50:09 +0000 (+0000)
Subject: Lazy patterns are like wild-cards for overlap warnings
X-Git-Url: http://git.megacz.com/?p=ghc-hetmet.git;a=commitdiff_plain;h=9ebd6baeb3955a9f3daa9b57a3d1b8f3b328893d

Lazy patterns are like wild-cards for overlap warnings

	MERGE TO STABLE

Fixes Trac #827
Test is should_compiler/ds058
---

diff --git a/compiler/deSugar/Check.lhs b/compiler/deSugar/Check.lhs
index 9aac5ce..097a008 100644
--- a/compiler/deSugar/Check.lhs
+++ b/compiler/deSugar/Check.lhs
@@ -623,7 +623,8 @@ simplify_pat pat@(WildPat gt) = pat
 simplify_pat (VarPat id)      = WildPat (idType id) 
 simplify_pat (VarPatOut id _) = WildPat (idType id) 	-- Ignore the bindings
 simplify_pat (ParPat p)       = unLoc (simplify_lpat p)
-simplify_pat (LazyPat p)      = unLoc (simplify_lpat p)
+simplify_pat (LazyPat p)      = WildPat (hsPatType p)	-- For overlap and exhaustiveness checking
+							-- purposes, a ~pat is like a wildcard
 simplify_pat (BangPat p)      = unLoc (simplify_lpat p)
 simplify_pat (AsPat id p)     = unLoc (simplify_lpat p)
 simplify_pat (SigPatOut p _)  = unLoc (simplify_lpat p)	-- I'm not sure this is right