[GHC] #14880: GHC panic: updateRole

[GHC]

#14880: GHC panic: updateRole
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        Reporter:  RyanGlScott       |                Owner:  goldfire
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:  8.8.1
       Component:  Compiler (Type    |              Version:  8.2.2
  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:  #15076            |  Differential Rev(s):  Phab:D4769
       Wiki Page:                    |
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Comment (by tdammers):

 I'm not done merging yet, unfortunately. I have rebased your patch onto
 the pre-patch master branch, but I still have to combine that with the
 rest of the #14880 patch, which is a bit tricky because both perform
 similar refactorings (factor out a private worker function for
 `tyCoVarsOf`...), but for different reasons. I'm afraid the easiest way is
 going to be to take the patch as is, and then manually re-engineer the
 `-accum` change from there.

 Richard did add some test cases though, and we have the existing tests
 that highlighted the regression in the first place (one of them is what
 we've been using throughout here).

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14880#comment:102>
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