[GHC] #9590: AMP breaks `haskell2010` package

[GHC]

#9590: AMP breaks `haskell2010` package
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              Reporter:  hvr         |            Owner:  ekmett
                  Type:  bug         |           Status:  new
              Priority:  high        |        Milestone:  7.10.1
             Component:  Core        |          Version:  7.9
  Libraries                          |         Keywords:  AMP
            Resolution:              |     Architecture:  Unknown/Multiple
      Operating System:              |       Difficulty:  Unknown
  Unknown/Multiple                   |       Blocked By:
       Type of failure:  GHC         |  Related Tickets:
  rejects valid program              |
             Test Case:              |
              Blocking:              |
Differential Revisions:              |
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Changes (by hvr):

 * cc: core-libraries-committee@… (added)


Comment:

 Replying to [comment:5 ekmett]:
 > Ack! Now I see what you mean.
 >
 > `Applicative` not even being in the package _is_ a problem.

 As a reminder this is still an issue, here's a suggestion together with a
 counter-argument:

 As a pragmatic solution, one could simply make available the `Applicative`
 typeclass in `haskell2010`. That way you can define `Monad` instance, iff
 you also define `Functor` **and** `Applicative` instances.

 However, now you end up with a "Haskell2010" program that works with GHC
 7.10 but not GHC 7.{0,2,4,8} (or any other strict-Haskell2010 mode
 compiler), as the program refers to a non-standard `Applicative` only
 available in GHC 7.10.

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9590#comment:11>
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