[GHC] #14773: MultiWayIf makes it easy to write partial programs that are not catched by -Wall

[GHC]

#14773: MultiWayIf makes it easy to write partial programs that are not catched by
-Wall
-------------------------------------+-------------------------------------
        Reporter:  SimonHengel       |                Owner:  sighingnow
            Type:  bug               |               Status:  patch
        Priority:  normal            |            Milestone:
       Component:  Compiler          |              Version:  8.2.2
      Resolution:                    |             Keywords:
                                     |  PatternMatchWarnings
Operating System:  Unknown/Multiple  |         Architecture:
                                     |  Unknown/Multiple
 Type of failure:  None/Unknown      |            Test Case:
                                     |  T14773a,T14773b
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):  Phab:D4400
       Wiki Page:                    |
-------------------------------------+-------------------------------------

Comment (by Ben Gamari <ben@…>):

 In [changeset:"e8e9f6a7a6d857efe6e3b2aec0c4964f9a8fa09a/ghc"
 e8e9f6a7/ghc]:
 {{{
 #!CommitTicketReference repository="ghc"
 revision="e8e9f6a7a6d857efe6e3b2aec0c4964f9a8fa09a"
 Improve exhaustive checking for guards in pattern bindings and MultiIf.

 Previously we didn't do exhaustive checking on MultiIf expressions
 and guards in pattern bindings.

 We can construct the `LMatch` directly from GRHSs or [LHsExpr]
 (MultiIf's alts) then feed it to checkMatches, without construct the
 MatchGroup and using function `matchWrapper`.

 Signed-off-by: HE, Tao <sighingnow at gmail.com>

 Test Plan: make test TEST="T14773a T14773b"

 Reviewers: bgamari, RyanGlScott, simonpj

 Reviewed By: bgamari, simonpj

 Subscribers: rwbarton, thomie, carter

 GHC Trac Issues: #14773

 Differential Revision: https://phabricator.haskell.org/D4400
 }}}

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14773#comment:13>
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