[GHC] #15419: GHC 8.6.1 regression (buildKindCoercion)

[GHC]

#15419: GHC 8.6.1 regression (buildKindCoercion)
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        Reporter:  RyanGlScott       |                Owner:  (none)
            Type:  bug               |               Status:  new
        Priority:  highest           |            Milestone:  8.6.1
       Component:  Compiler (Type    |              Version:  8.5
  checker)                           |
      Resolution:                    |             Keywords:  TypeInType
Operating System:  Unknown/Multiple  |         Architecture:
 Type of failure:  Compile-time      |  Unknown/Multiple
  crash or panic                     |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
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Changes (by RyanGlScott):

 * cc: goldfire (added)


Comment:

 Commit 3eaa55dcbcd860a035dfe2cae96866e96b008f67 (`Apply Note [EtaAppCo] in
 OptCoercion to another case`) is responsible for this regression.

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/15419#comment:1>
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