[GHC] #15740: Type family with higher-rank result is too accepting

[GHC]

#15740: Type family with higher-rank result is too accepting
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        Reporter:  goldfire          |                Owner:  (none)
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:
       Component:  Compiler          |              Version:  8.6.1
      Resolution:                    |             Keywords:  TypeFamilies,
                                     |  TypeInType
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):

 As noted in comment:16:ticket:11719, this behavior is a regression from
 GHC 8.2, which rejects those instances. The first commit to demonstrate
 this behavior is 4239238306e911803bf61fdda3ad356fd0b42e05 (Fix #12369 by
 being more flexible with data insts).

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/15740#comment:2>
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