[GHC] #11608: Possible type-checker regression in GHC 8.0 when compiling `microlens`

[GHC]

#11608: Possible type-checker regression in GHC 8.0 when compiling `microlens`
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        Reporter:  hvr               |                Owner:  simonpj
            Type:  bug               |               Status:  closed
        Priority:  highest           |            Milestone:  8.0.1
       Component:  Compiler (Type    |              Version:  8.0.1-rc2
  checker)                           |
      Resolution:  fixed             |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
                                     |  Unknown/Multiple
 Type of failure:  GHC rejects       |            Test Case:
  valid program                      |  typecheck/should_compile/T11608
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
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Comment (by simonpj):

 Jolly good.

 * The `polykinds` ones are discussed in #11648
 * `TcCoercibleFail` is really supposed to fail with `-DDEBUG` (exponential
 sized types)
 * I have a patch coming for the other three.

 So this is good news really.

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11608#comment:17>
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