[GHC] #13083: Constraint solving failure with Coercible + type family + newtype

[GHC]

#13083: Constraint solving failure with Coercible + type family + newtype
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        Reporter:  conal             |                Owner:
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:
       Component:  Compiler (Type    |              Version:  8.0.1
  checker)                           |
      Resolution:                    |             Keywords:  Coercible
Operating System:  MacOS X           |         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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Comment (by goldfire):

 I'm afraid I don't see how comment:1 applies. The type of `foo` seems to
 be a straightforward specialization of the type of `bar`. So it seems this
 should work.

 Confirmed reproducible in a fairly recent HEAD.

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13083#comment:2>
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