[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 PeterTrsko):

 Seems that `fail` is "integral part" of the `Q` monad and `fail` is part
 of its contract with the user. The same goes for `Quasy` type class. See
 e.g. `qReport` and `qRecover`.

 In my opinion, the only way to correctly preserve the same semantics,
 under `MonadFailDesugaring`, is to put `MonadFail` as a superclass of
 `Quasy`.

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11661#comment:7>
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