[GHC] #9117: Coercible constraint solver misses one

[GHC]

#9117: Coercible constraint solver misses one
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              Reporter:  goldfire    |            Owner:
                  Type:  bug         |           Status:  new
              Priority:  normal      |        Milestone:
             Component:  Compiler    |          Version:  7.8.2
            Resolution:              |         Keywords:
      Operating System:              |     Architecture:  Unknown/Multiple
  Unknown/Multiple                   |       Difficulty:  Unknown
       Type of failure:              |       Blocked By:
  None/Unknown                       |  Related Tickets:
             Test Case:              |
              Blocking:              |
Differential Revisions:              |
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Changes (by nomeata):

 * owner:  nomeata =>


Comment:

 This ticket started with `eta :: Coercible f g => Coercion (f a) (g a)`
 and then discussed the order of our existing solving steps (which was then
 changed). But nothing happened about `eta :: Coercible f g => Coercion (f
 a) (g a)`.

 Is there a real use case for this? Do we have an idea how to integrate
 that?

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9117#comment:31>
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