X-Git-Url: http://git.megacz.com/?p=ghc-hetmet.git;a=blobdiff_plain;f=compiler%2Fspecialise%2FRules.lhs;h=6a4dff08088203cc634894cc394be1558a2737be;hp=65975f81cb537372135332c1b567c558775ff8a7;hb=7ecf87b26ca50c1b6def186c32f4dfa0e9cedb97;hpb=c0fe534fbf3d3e30a6f35b355da86e6f18601348

diff --git a/compiler/specialise/Rules.lhs b/compiler/specialise/Rules.lhs
index 65975f8..6a4dff0 100644
--- a/compiler/specialise/Rules.lhs
+++ b/compiler/specialise/Rules.lhs
@@ -123,11 +123,13 @@ ruleCantMatch :: [Maybe Name] -> [Maybe Name] -> Bool
 -- It's only a one-way match; unlike instance matching we 
 -- don't consider unification
 -- 
--- Notice that there is no case
---	ruleCantMatch (Just n1 : ts) (Nothing : as) = True
--- Reason: a local variable 'v' in the actuals might 
--- 	   have an unfolding which is a global.
---	   This quite often happens with case scrutinees.
+-- Notice that [_$_]
+--	ruleCantMatch [Nothing] [Just n2] = False
+--      Reason: a template variable can be instantiated by a constant
+-- Also:
+--	ruleCantMatch [Just n1] [Nothing] = False
+--      Reason: a local variable 'v' in the actuals might [_$_]
+
 ruleCantMatch (Just n1 : ts) (Just n2 : as) = n1 /= n2 || ruleCantMatch ts as
 ruleCantMatch (t       : ts) (a       : as) = ruleCantMatch ts as
 ruleCantMatch ts	     as		    = False