[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):

 NonDetFV (`NDFV`) speed / allocations test still running.

 While writing the code for `NDFV`, one thing caught my eye however: the
 `delFV` / `delFVs` functions, rather than actually remove anything from
 the `have` list and the `haveSet`, *add* to the `in_scope` set; naturally,
 rewriting this in terms of `VarSet`, where the `delVarSet` function
 actually removes the var from the set, will change performance
 characteristics, one way or the other, depending on the situation.

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14880#comment:81>
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