[GHC] #13353: foldr/nil rule not applied consistently

[GHC]

#13353: foldr/nil rule not applied consistently
-------------------------------------+-------------------------------------
        Reporter:  nomeata           |                Owner:  (none)
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:
       Component:  Compiler          |              Version:  8.1
      Resolution:                    |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
 Type of failure:  Compile-time      |  Unknown/Multiple
  performance bug                    |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
-------------------------------------+-------------------------------------

Comment (by simonpj):

 > Also, in all cases, map id remains, which should not be the case.

 I think we are missing
 {{{
 {-# RULES
 "mapFB/id"     forall c. mapFB c (\x->x) = c
   #-}
 }}}
 Want to try adding that?

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13353#comment:4>
GHC <http://www.haskell.org/ghc/>
The Glasgow Haskell Compiler