[GHC] #11661: Missing MonadFail instance for Q monad from TemplateHaskell

[GHC]

#11661: Missing MonadFail instance for Q monad from TemplateHaskell
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        Reporter:  PeterTrsko        |                Owner:
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:
       Component:  Template Haskell  |              Version:  8.0.1-rc2
      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 quchen):

 The question is, what do we gain? It would not be clear why Quasi has a
 MonadFail superclass, and I cannot imagine many functions might want to
 make use of Q's `fail`.

 Are we in danger of breaking any code because `fail` is removed from
 `Monad`, does TH rely on its existence? Maybe we should fix those cases
 instead.

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11661#comment:5>
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