[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:  #14200            |  Differential Rev(s):
       Wiki Page:                    |
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Changes (by dfeuer):

 * cc: dfeuer (added)


Comment:

 In my opinion, there are two reasonable ways forward:

 1. Adopt `Monad` of no `return`, and deprecate and remove `WrappedMonad`
 altogether.

 2. Change the definition of `pure` for `WrappedMonad` back to using
 `return`, which will make it usable, among other things, for defining
 `Functor` and `Applicative` instances using `DerivingVia`.

 1 may happen (I personally hope so), but probably not this year. I don't
 personally see any serious downside to proceeding with 2 for the time
 being.

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13876#comment:9>
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