[GHC] #11642: Heterogeneous type equality evidence ignored

[GHC]

#11642: Heterogeneous type equality evidence ignored
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        Reporter:  bgamari           |                Owner:
            Type:  bug               |               Status:  new
        Priority:  highest           |            Milestone:  8.0.1
       Component:  Compiler (Type    |              Version:  7.10.3
  checker)                           |
      Resolution:                    |             Keywords:  TypeInType
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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Changes (by simonpj):

 * keywords:   => TypeInType


Comment:

 Richard I think this needs your loving care.  I had a look but ran out of
 time in a maze of twisty little casts, all alike.

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11642#comment:8>
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