X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=ghc%2Fcompiler%2FcoreSyn%2FCorePrep.lhs;h=298e599ef2a6d1e68c26deec9c1d357733d3970f;hb=3b9d7c8181f6edd130fb93768e4f1e32977a738c;hp=5a4b636896ee5cb501e9f411ebd5c4224258cc01;hpb=93436263afc077d487937c45a12f38ad841dc9f0;p=ghc-hetmet.git

diff --git a/ghc/compiler/coreSyn/CorePrep.lhs b/ghc/compiler/coreSyn/CorePrep.lhs
index 5a4b636..298e599 100644
--- a/ghc/compiler/coreSyn/CorePrep.lhs
+++ b/ghc/compiler/coreSyn/CorePrep.lhs
@@ -427,6 +427,12 @@ mkLocalNonRec bndr dem floats rhs
 	--     code compiled without -O.  The case in point is data constructor
 	--     wrappers.
 	--
+	-- NB2: we have to be careful that the result of etaExpand doesn't
+	--    invalidate any of the assumptions that CorePrep is attempting
+	--    to establish.  One possible cause is eta expanding inside of
+	--    an SCC note - we're now careful in etaExpand to make sure the
+	--    SCC is pushed inside any new lambdas that are generated.
+	--
     getUniquesUs		`thenUs` \ us ->
     let
 	rhs' = etaExpand (exprArity rhs) us rhs bndr_ty