[GHC] #15347: QuantifiedConstraints: Implication constraints with type families don't work

[GHC]

#15347: QuantifiedConstraints: Implication constraints with type families don't
work
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        Reporter:  aaronvargo        |                Owner:  (none)
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:
       Component:  Compiler (Type    |              Version:  8.5
  checker)                           |             Keywords:
      Resolution:                    |  QuantifiedConstraints
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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Comment (by aaronvargo):

 Replying to [comment:16 simonpj]:

 I thought I'd once seen a ticket for this, and I've managed to find it:
 see #3490, where you write:

 > The easiest way forward is to re-express your program using type
 functions

 Also, on second thought, what I said in comment:18 won't work.

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/15347#comment:19>
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