[GHC] #15624: defer-type-errors and equality constraints

10 Sep 2018

      #15624: defer-type-errors and equality constraints
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           Reporter:  monoidal       |             Owner:  (none)
               Type:  bug            |            Status:  new
           Priority:  low            |         Milestone:  8.8.1
          Component:  Compiler       |           Version:  8.4.3
  (Type checker)                     |
           Keywords:                 |  Operating System:  Unknown/Multiple
       Architecture:                 |   Type of failure:  None/Unknown
  Unknown/Multiple                   |
          Test Case:                 |        Blocked By:
           Blocking:                 |   Related Tickets:
Differential Rev(s):                 |         Wiki Page:
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 Consider

 {{{
 {-# OPTIONS_GHC -fdefer-type-errors #-}
 x = const True ('a' + 'a')
 y = const True (not 'a')
 }}}

 Currently `x` is True, but `y` is undefined. I think it would make sense
 for both to be True.

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Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/15624
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