[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:  new
        Priority:  highest           |            Milestone:  8.0.1
       Component:  Compiler (Type    |              Version:  8.0.1-rc2
  checker)                           |
      Resolution:                    |             Keywords:
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 simonpj):

 NB: the `isTcTyVar` could conceivably cause extra ASSERT failures when
 DEBUG is on.  I didn't see any, but keep your eyes open.

 However, ignoring them (ie no `-DDEBUG`) is simply what happens today and
 is fine. So things will not be worse.

 Simon

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11608#comment:11>
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