[GHC] #14434: GHC 8.2.1 picks wrong instances with -O in a presence of an OVERLAPPABLE instance

[GHC]

#14434: GHC 8.2.1 picks wrong instances with -O in a presence of an OVERLAPPABLE
instance
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        Reporter:  dredozubov        |                Owner:  (none)
            Type:  bug               |               Status:  merge
        Priority:  high              |            Milestone:  8.2.3
       Component:  Compiler          |              Version:  8.2.1
      Resolution:                    |             Keywords:
Operating System:  Linux             |         Architecture:  x86_64
                                     |  (amd64)
 Type of failure:  Incorrect result  |            Test Case:
  at runtime                         |  typecheck/should_compile/T14434
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
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Comment (by dredozubov):

 Thanks for the fix! Unfortunately I was unable to build our application
 with ghc HEAD due to broken dependencies.

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14434#comment:7>
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