[GHC] #13772: Cannot put HasCallStack on instances

[GHC]

#13772: Cannot put HasCallStack on instances
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        Reporter:  augustss          |                Owner:  (none)
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:
       Component:  Compiler          |              Version:  8.0.1
      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 augustss):

 So can you explain where I should put my HasCallstack constraint in my
 Monoid instance?
 I'd like to get a call stack when mempty is used and it calls error.

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13772#comment:3>
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