[GHC] #10792: Bounded Enums [minBound..maxBound] produces runtime error

[GHC]

#10792: Bounded Enums [minBound..maxBound] produces runtime error
-------------------------------------+-------------------------------------
              Reporter:              |             Owner:  ekmett
  AlexanderThiemann                  |
                  Type:  bug         |            Status:  new
              Priority:  normal      |         Milestone:
             Component:  Core        |           Version:  7.10.2
  Libraries                          |
              Keywords:              |  Operating System:  Linux
          Architecture:              |   Type of failure:  Runtime crash
  Unknown/Multiple                   |
             Test Case:              |        Blocked By:
              Blocking:              |   Related Tickets:
Differential Revisions:              |
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 Consider this code:

 {{{#!hs
 data MultiHeader
    = MultiHeaderCacheControl
    | MultiHeaderConnection
    | MultiHeaderContentEncoding
    -- ...
      deriving (Show, Eq, Enum, Bounded, Generic)

 instance Hashable MultiHeader

 multiHeaderCI :: MultiHeader -> CI.CI BS.ByteString
 multiHeaderCI mh =
     case mh of
       MultiHeaderCacheControl -> "Cache-Control"
       MultiHeaderConnection -> "Connection"
       MultiHeaderContentEncoding -> "Content-Encoding"
       -- ...

 multiHeaderMap :: HM.HashMap (CI.CI BS.ByteString) MultiHeader
 multiHeaderMap =
     HM.fromList $ flip map [minBound..maxBound] $ \mh ->
     (multiHeaderCI mh, mh)
 }}}

 (derived from
 https://github.com/agrafix/Spock/blob/9c19c0159d99783aabf896d2742e231a5e85e0a5/src/Web/Spock/Internal/Wire.hs#L83-L121
 )

 When the multiHeaderMap accessed, a runtime error on GHC7.10.2 running on
 *some* [0] [1] Linux architectures is thrown. It does not occur on Mac or
 the travis build infrastructure [2].

 {{{
 uncaught exception: ErrorCall (toEnum{MultiHeader}: tag (-12565) is
 outside of enumeration's range (0,12))
 }}}

 I've marked the bug with 'core libraries', but I am not certain that
 that's the origin of it.

 [0]: https://github.com/agrafix/Spock/issues/44 (Hydra / NixOS?)
 [1]: We've also seen it happen when used in docker with ubuntu:14.04 base
 image
 [2]: https://travis-ci.org/agrafix/Spock/builds/76877783

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10792>
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