[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:"8ae263ceb3566a7c82336400b09cb8f381217405/ghc" 8ae263c/ghc]:
 {{{
 #!CommitTicketReference repository="ghc"
 revision="8ae263ceb3566a7c82336400b09cb8f381217405"
 Make Semigroup a superclass of Monoid (re #14191)

 Unfortunately, this requires introducing a couple of .hs-boot files to
 break up import cycles (mostly to provide class & typenames in order to
 be able to write type signatures).

 This does not yet re-export `(<>)` from Prelude (while the class-name
 `Semigroup` is reexported); that will happen in a future commit.

 Test Plan: local ./validate passed

 Reviewers: ekmett, austin, bgamari, erikd, RyanGlScott

 Reviewed By: ekmett, RyanGlScott

 GHC Trac Issues: #14191

 Differential Revision: https://phabricator.haskell.org/D3927
 }}}

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14191#comment:4>
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