[GHC] #15144: Type inference regression between GHC 8.0.2 and 8.2.2

[GHC]

#15144: Type inference regression between GHC 8.0.2 and 8.2.2
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        Reporter:  RyanGlScott       |                Owner:  (none)
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:  8.6.1
       Component:  Compiler (Type    |              Version:  8.2.2
  checker)                           |
      Resolution:                    |             Keywords:  TypeFamilies
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 RyanGlScott):

 What's odd is that things work out alright if I write an explicit type
 signature:

 {{{#!hs
 g :: Coercible (F a) b => Proxy a -> F a -> b
 g p x = f p x
 }}}

 It's only when the type is inferred that it becomes less general.

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/15144#comment:3>
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