[GHC] #9586: Implement Traversable/Foldable-Burning-Bridges Proposal

[GHC]

#9586: Implement Traversable/Foldable-Burning-Bridges Proposal
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              Reporter:  hvr         |            Owner:  hvr
                  Type:  task        |           Status:  new
              Priority:  normal      |        Milestone:  7.10.1
             Component:              |          Version:
  libraries/base                     |         Keywords:
            Resolution:              |     Architecture:  Unknown/Multiple
      Operating System:              |       Difficulty:  Difficult (2-5
  Unknown/Multiple                   |  days)
       Type of failure:              |       Blocked By:
  None/Unknown                       |  Related Tickets:
             Test Case:              |
              Blocking:              |
Differential Revisions:  Phab:D209   |
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Comment (by Herbert Valerio Riedel <hvr@…>):

 In [changeset:"c0fa383d9109800a4e46a81b418f1794030ba1bd/ghc"]:
 {{{
 #!CommitTicketReference repository="ghc"
 revision="c0fa383d9109800a4e46a81b418f1794030ba1bd"
 Export `Traversable()` and `Foldable()` from Prelude

 This exposes *only* the type-classes w/o any of their methods.
 This is the very first step for implementing BPP (see #9586), which
 already requires breaking up several import-cycles leading back to
 `Prelude`.

 Ideally, importing `Prelude` should be avoided in most `base` modules,
 as `Prelude` does not define any entities, but rather re-exports
 existing ones.

 Test Plan: validate passes

 Reviewers: ekmett, austin

 Reviewed By: ekmett, austin

 Subscribers: simonmar, ezyang, carter

 Differential Revision: https://phabricator.haskell.org/D209

 GHC Trac Issues: #9586
 }}}

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9586#comment:2>
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