[GHC] #14218: GHC.Stack.HasCallStack not compatible with constraint synonyms

[GHC]

#14218: GHC.Stack.HasCallStack not compatible with constraint synonyms
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        Reporter:  ntc2              |                Owner:  (none)
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:
       Component:  Compiler          |              Version:  8.2.1
      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 bgamari):

 > Ben's explanation sounds plausible to me, though I didn't realize
 constraint synonyms worked this way.

 I actually didn't realize it either until I looked at the tc-trace output.
 I also don't know whether there is a good reason (other than efficiency)
 why they *must* be implemented this way.

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14218#comment:3>
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