[GHC] #14065: Type inference

[GHC]

#14065: Type inference
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        Reporter:  zaoqi             |                Owner:  (none)
            Type:  bug               |               Status:  closed
        Priority:  normal            |            Milestone:
       Component:  Compiler (Type    |              Version:  8.0.2
  checker)                           |
      Resolution:  invalid           |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
                                     |  Unknown/Multiple
 Type of failure:  None/Unknown      |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
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Comment (by bgamari):

 To clarify, I've confirmed with Simon that this is indeed the expected
 behavior. The typechecker is conservative in inferring underneath pattern
 matches on equalities. See Chapter 6 of the
 [[http://research.microsoft.com/en-us/um/people/simonpj/papers/constraints
 /jfp-outsidein.pdf|OutsideIn paper]] to see the complications that arise
 when you try to infer under such matches.

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14065#comment:3>
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