[GHC] #15546: Display coaxiom branch incompatibilities in GHCi

[GHC]

#15546: Display coaxiom branch incompatibilities in GHCi
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        Reporter:  mniip             |                Owner:  (none)
            Type:  feature request   |               Status:  new
        Priority:  normal            |            Milestone:  8.6.1
       Component:  GHCi              |              Version:  8.4.3
      Resolution:                    |             Keywords:  TypeFamilies,
                                     |  GHCi
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 simonpj):

 I'm sorry I'm lost.  What does "that type family compatibility checks do
 not reduce the LHS and expect the equality to trivially hold" mean?  What
 is "this restriction"?  What is illustrated by the example?  Is it a bug?
 Thanks

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/15546#comment:5>
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