[GHC] #13876: Check 'pure' method of 'Applicative (WrappedMonad m)'

[GHC]

#13876: Check 'pure' method of 'Applicative (WrappedMonad m)'
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        Reporter:  Iceland_jack      |                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 RyanGlScott):

 I think I agree with bgamari here. Although we haven't removed `return`
 from `Monad` entirely, we've already taken the important step of
 refactoring just about all of `base` to define things first and foremost
 in terms of `pure`, and defining `return = pure` elsewhere. At this point,
 making another change to the semantics of `WrapMonad`'s `return` instance
 just for this use case feels pointless in the long run since, as others
 have noted, `return` really should work the same as `pure` from here on
 out in anticipation of `return`'s eventual removal from the `Monad` class.

 As for a solution to your problem, I'd suggest your idea of having another
 wrapper `newtype` that uses `Pointed` and `Monad` to retrofit
 `Applicative` instances.

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13876#comment:5>
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