[GHC] #11650: Documentation does not mention that default definitions for Alternative(some, many) can easily blow up

[GHC]

#11650: Documentation does not mention that default definitions for
Alternative(some, many) can easily blow up
-------------------------------------+-------------------------------------
        Reporter:  bgamari           |                Owner:
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:
       Component:  Documentation     |              Version:  7.10.3
      Resolution:                    |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
                                     |  Unknown/Multiple
 Type of failure:  None/Unknown      |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
-------------------------------------+-------------------------------------

Comment (by Ben Gamari <ben@…>):

 In [changeset:"171d95df24dc2d9d0c1a3af9e75f021438a7da50/ghc"
 171d95df/ghc]:
 {{{
 #!CommitTicketReference repository="ghc"
 revision="171d95df24dc2d9d0c1a3af9e75f021438a7da50"
 Missing Proxy instances, make U1 instance more Proxy-like

 This accomplishes three things:

 * Adds missing `Alternative`, `MonadPlus`, and `MonadZip` instances for
   `Proxy`
 * Adds a missing `MonadPlus` instance for `U1`
 * Changes several existing `U1` instances to use lazy pattern-matching,
   exactly how `Proxy` does it (in case we ever replace `U1` with
   `Proxy`). This is technically a breaking change (albeit an extremely
   minor one).

 Test Plan: ./validate

 Reviewers: austin, ekmett, hvr, bgamari

 Reviewed By: bgamari

 Subscribers: thomie

 Differential Revision: https://phabricator.haskell.org/D1962

 GHC Trac Issues: #11650
 }}}

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11650#comment:12>
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