Re: #16365: Inconsistency in quantified constraint solving

"GHC" <[email protected]> Wed, 06 Mar 2019 20:21:23 -0000

Newsgroups	gmane.comp.lang.haskell.glasgow.bugs
Message-ID	<[email protected]>

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#16365: Inconsistency in quantified constraint solving
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        Reporter:  RyanGlScott       |                Owner:  (none)
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:
       Component:  Compiler          |              Version:  8.6.3
      Resolution:                    |             Keywords:
                                     |  QuantifiedConstraints
Operating System:  Unknown/Multiple  |         Architecture:
 Type of failure:  GHC rejects       |  Unknown/Multiple
  valid program                      |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
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Comment (by RyanGlScott):

 Note that this is quite annoying in practice for the `singletons` library,
 as the existence of this bug prevents it from using `deriving` to generate
 its `Show` instances, instead forcing it to laboriously generate `Show`
 instances with Template Haskell.

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/16365#comment:1>