[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):

 OK, so; replacing the `delNDFV` function with an implementation that
 doesn't touch the `in_scope` set at all, and instead removes items from
 the `acc` set, we get practically identical performance as with `NDFV` in
 its previous incarnation. Which means that 2. is not the culprit; the
 `in_scope` set seems to not make a difference, suggesting that we aren't
 really deleting a substantial number of elements from the set here.

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14880#comment:86>
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