[GHC] #15696: Derived Ord instance for enumerations with more than 8 elements seems to be incorrect

GHC ghc-devs at haskell.org
Sat Oct 13 21:59:04 UTC 2018


#15696: Derived Ord instance for enumerations with more than 8 elements seems to be
incorrect
-------------------------------------+-------------------------------------
        Reporter:  mrkkrp            |                Owner:  osa1
            Type:  bug               |               Status:  patch
        Priority:  highest           |            Milestone:  8.6.2
       Component:  Compiler          |              Version:  8.6.1
      Resolution:                    |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
 Type of failure:  Incorrect result  |  Unknown/Multiple
  at runtime                         |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:  #14677, #15155    |  Differential Rev(s):  Phab:D5196,
       Wiki Page:                    |  Phab:D5201, Phab:D5226
-------------------------------------+-------------------------------------
Changes (by bgamari):

 * differential:  Phab:D5196, Phab:D5201 => Phab:D5196, Phab:D5201,
                   Phab:D5226


Comment:

 I gave Secondly from comment:77 a try while waiting for GHC 8.4.4 builds.
 The result is Phab:D5226.

 However, the approach presented does seem a bit odd since the demand
 resulting from demand analysis is still conservative; we merely make up
 for this conservatism in worker-wrapper. However, this doesn't help other
 (hypothetical) consumers of demand analysis. Perhaps it would be good to
 open a ticket to ensure we don't forget about this limitation.

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/15696#comment:80>
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