[GHC] #14191: Implement Semigroup as a superclass of Monoid Proposal (Phase 2)

[GHC]

#14191: Implement Semigroup as a superclass of Monoid Proposal (Phase 2)
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        Reporter:  hvr               |                Owner:  hvr
            Type:  task              |               Status:  new
        Priority:  normal            |            Milestone:  8.4.1
       Component:  libraries/base    |              Version:  8.2.1
      Resolution:                    |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
                                     |  Unknown/Multiple
 Type of failure:  None/Unknown      |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:  #10365            |  Differential Rev(s):  phab:D3927
       Wiki Page:                    |
  prime:Libraries/Proposals/SemigroupMonoid|
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Comment (by Herbert Valerio Riedel <hvr@…>):

 In [changeset:"10ca8018900364579123bf3912202176d338d3c6/ghc" 10ca801/ghc]:
 {{{
 #!CommitTicketReference repository="ghc"
 revision="10ca8018900364579123bf3912202176d338d3c6"
 Generalise constraint on `instance Monoid (Maybe a)` to Semigroup

 This now becomes possible due to the introduction of the
 Semigroup=>Monoid superclass relation (see #14191).

 Reviewers: ekmett, RyanGlScott, austin, bgamari

 Reviewed By: ekmett, RyanGlScott, bgamari

 Subscribers: rwbarton, thomie

 Differential Revision: https://phabricator.haskell.org/D3972
 }}}

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14191#comment:11>
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