[GHC] #15135: Overlapping typeclass instance selection depends on the optimisation level

[GHC]

#15135: Overlapping typeclass instance selection depends on the optimisation level
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        Reporter:  nicuveo           |                Owner:  (none)
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:  8.8.1
       Component:  Compiler          |              Version:  8.4.2
      Resolution:                    |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
                                     |  Unknown/Multiple
 Type of failure:  None/Unknown      |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
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Comment (by baramoglo):

 Replying to [comment:4 AntC]:
 > BTW what happens if you change all the pragmas to `OVERLAPS`?

 Then it works correctly.

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/15135#comment:5>
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