[GHC] #13227: Loss of full laziness in mapFB

[GHC]

#13227: Loss of full laziness in mapFB
-------------------------------------+-------------------------------------
        Reporter:  simonpj           |                Owner:  nomeata
            Type:  bug               |               Status:  closed
        Priority:  normal            |            Milestone:
       Component:  Compiler          |              Version:  8.0.1
      Resolution:  fixed             |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
                                     |  Unknown/Multiple
 Type of failure:  None/Unknown      |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):  Phab:D3067
       Wiki Page:                    |
-------------------------------------+-------------------------------------

Comment (by nomeata):

 In fact, I tried doing that right when you posted comment:9. I tried  to
 modify so that unwanted floating would be detectable in the output by some
 carefully placed `trace`, but I did not manage that. (I dislike tests that
 grep in `-ddump-simpl`, they are too fragile.)

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13227#comment:20>
GHC <http://www.haskell.org/ghc/>
The Glasgow Haskell Compiler