[GHC] #10756: Allow users to indicate inaccessible patterns

[GHC]

#10756: Allow users to indicate inaccessible patterns
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        Reporter:  edsko             |                   Owner:
            Type:  feature request   |                  Status:  new
        Priority:  normal            |               Milestone:
       Component:  Compiler          |                 Version:  7.10.2
      Resolution:                    |                Keywords:
Operating System:  Unknown/Multiple  |            Architecture:
                                     |  Unknown/Multiple
 Type of failure:  None/Unknown      |               Test Case:
      Blocked By:                    |                Blocking:
 Related Tickets:                    |  Differential Revisions:
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Changes (by YitzGale):

 * cc: gale@… (added)


Comment:

 I propose a modification: that {{{impossible}}} not become a full-fledged
 keyword, but rather that it only be given special meaning in the context
 of a pattern expression.

 I leave as an open question how this should work in a pattern guard.

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10756#comment:6>
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