[GHC] #8695: Arithmetic overflow from (minBound :: Int) `quot` (-1)

[GHC]

#8695: Arithmetic overflow from (minBound :: Int) `quot` (-1)
-------------------------------------+-------------------------------------
       Reporter:  rleslie            |             Owner:
           Type:  bug                |            Status:  new
       Priority:  normal             |         Milestone:
      Component:                     |           Version:  7.6.3
  libraries/haskell2010              |  Operating System:  Unknown/Multiple
       Keywords:                     |   Type of failure:  Incorrect result
   Architecture:  Unknown/Multiple   |  at runtime
     Difficulty:  Unknown            |         Test Case:
     Blocked By:                     |          Blocking:
Related Tickets:                     |
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 According to the documentation for Data.Int, “All arithmetic is performed
 modulo 2!^n, where n is the number of bits in the type.”

 However, this promise is broken by the following exception:

 {{{
 Prelude> (minBound :: Int) `quot` (-1)
 *** Exception: arithmetic overflow
 }}}

 (This also occurs with Int8, Int16, Int32, and Int64, and likewise for
 `div`.)

 If all arithmetic is performed modulo 2!^n, I would rather expect the
 above to evaluate to `minBound`, since after all `minBound * (-1) ==
 minBound`. The fact that an exception is raised adds an unnecessary burden
 in pure code to ensure `quot` (or `div`) is never called with these
 specific arguments.

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/8695>
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