I have a question about {-# RULES #-} pragmas. Here is a very simple attempt to use them: module Simplest where {-# RULES "simplestRule" forall x. id (id x) = x #-} myDefn = id (id 42) I want to verify whether ghc-6.4.1 does actually fire this rule, but have so far been unable to do so. According to the manual (section 7.10.5), the flag -ddump-rules should list "simplestRule" if it has been parsed correctly, and -ddump-simpl-stats should list the number of times it has fired. But it does not appear in either listing. Reasoning that I have the syntax wrong, I have tried numerous variations on the indentation, added type signatures, etc., all to no avail. So what am I doing wrong? And is there any way to ask the compiler to give a warning if the RULES pragma contains errors? Regards, Malcolm