From: simonpj@microsoft.com <unknown>
Date: Thu, 25 Nov 2010 17:21:38 +0000 (+0000)
Subject: Make SpecConstr "look through" identity coercions
X-Git-Url: http://git.megacz.com/?a=commitdiff_plain;h=45a61df30f95b22d4818b6e3e3622707911bde03;p=ghc-hetmet.git

Make SpecConstr "look through" identity coercions
---

diff --git a/compiler/specialise/SpecConstr.lhs b/compiler/specialise/SpecConstr.lhs
index cbe1c0b..0b61a57 100644
--- a/compiler/specialise/SpecConstr.lhs
+++ b/compiler/specialise/SpecConstr.lhs
@@ -1549,6 +1549,9 @@ argToPat env in_scope val_env (Case scrut _ _ [(_, _, rhs)]) arg_occ
 -}
 
 argToPat env in_scope val_env (Cast arg co) arg_occ
+  | isIdentityCoercion co     -- Substitution in the SpecConstr itself
+                              -- can lead to identity coercions
+  = argToPat env in_scope val_env arg arg_occ
   | not (ignoreType env ty2)
   = do	{ (interesting, arg') <- argToPat env in_scope val_env arg arg_occ
 	; if not interesting then