[GHC] #8581: Pattern synonym used in an expression context could have different constraints to pattern used in a pattern context

GHC ghc-devs at haskell.org
Sat Dec 19 18:11:18 UTC 2015


#8581: Pattern synonym used in an expression context could have different
constraints to pattern used in a pattern context
-------------------------------------+-------------------------------------
        Reporter:  cactus            |                Owner:
            Type:  feature request   |               Status:  new
        Priority:  normal            |            Milestone:  8.0.1
       Component:  Compiler          |              Version:
      Resolution:                    |             Keywords:
                                     |  PatternSynonyms
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 mpickering):

 This plan runs into problems as we can't given the matcher and builder
 different `Name`s as they are both in the same namespace so there is no
 way to disambiguate which one we should choose. As a result, the
 dependency analysis is still too coarse, all occurrences point to the same
 thing which is not what we want.

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/8581#comment:33>
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