[GHC] #10715: Possible regression in Coercible a (X a) between 7.8 and 7.10

[GHC]

#10715: Possible regression in Coercible a (X a) between 7.8 and 7.10
-------------------------------------+-------------------------------------
        Reporter:  inaki             |                   Owner:  goldfire
            Type:  bug               |                  Status:  merge
        Priority:  normal            |               Milestone:  7.10.3
       Component:  Compiler          |                 Version:  7.10.1
      Resolution:                    |                Keywords:
Operating System:  Unknown/Multiple  |            Architecture:
                                     |  Unknown/Multiple
 Type of failure:  GHC rejects       |               Test Case:
  valid program                      |  typecheck/should_fail/T10715{,b}
      Blocked By:                    |                Blocking:
 Related Tickets:                    |  Differential Revisions:  Phab:D1263
-------------------------------------+-------------------------------------
Changes (by goldfire):

 * testcase:   => typecheck/should_fail/T10715{,b}
 * status:  patch => merge
 * milestone:   => 7.10.3


Comment:

 Merge only if convenient -- this does nothing but improve error messages.

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10715#comment:16>
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