Bounded Enums [minBound..maxBound] produces runtime error

Consider this code:

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

Trac metadata

Trac field	Value
Version	7.10.2
Type	Bug
TypeOfFailure	OtherFailure
Priority	normal
Resolution	Unresolved
Component	Core Libraries
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