[GHC] #13644: overloaded name used in record pattern matching leads to panic! (the 'impossible' happened) in ghc

[GHC]

#13644: overloaded name used in record pattern matching leads to panic!  (the
'impossible' happened) in ghc
-------------------------------------+-------------------------------------
        Reporter:  pjljvdlaar        |                Owner:  (none)
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:  8.4.1
       Component:  Compiler          |              Version:  8.0.2
      Resolution:                    |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
 Type of failure:  Compile-time      |  Unknown/Multiple
  crash or panic                     |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:  #13840, #13973,   |  Differential Rev(s):
  #14087                             |
       Wiki Page:                    |
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Comment (by adamgundry):

 @simonpj thanks for pointing me to this ticket.

 > The problem is in TcPat.find_field_ty but I can't see how to cleanly fix
 it.

 @mpickering part of the fix is surely to compare the selector names (which
 we have available). I've implemented this in
 52110a7966848538583acb65f6e064aadc751260 and it fixes the original test
 case.

 However, the related bug #13847 remains: this patch is too liberal as it
 accepts examples where the field label is in scope only qualified, but it
 is used unqualified, and `DisambiguateRecordFields` is not enabled.
 Several of the other related bugs demonstrate this, so my patch causes
 them to be accepted (without a panic, but without an error either).

 I'm out of time to investigate further for now, unfortunately.

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13644#comment:16>
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