[GHC] #10653: PatternSynonyms should be imported/exported as part of the wildcard notation

[GHC]

#10653: PatternSynonyms should be imported/exported as part of the wildcard
notation
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        Reporter:  gridaphobe        |                   Owner:  mpickering
            Type:  feature request   |                  Status:  new
        Priority:  high              |               Milestone:  8.0.1
       Component:  Compiler          |                 Version:  7.11
      Resolution:                    |                Keywords:
                                     |  PatternSynonyms, pattern synonyms
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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Comment (by goldfire):

 Your examples agree with my understanding of this proposal.

 > A possible restriction might be that you can only add `P` to an export
 of a data type `T` if `P`'s type has form `... -> T t1 ..tn`.

 This has been suggested. I think it's a good idea. My guess is that it was
 removed because of concerns that the whole thing has to be resolved by the
 renamer. But I actually don't think this is problematic at all. The whole
 thing //is// resolved by the renamer. It's just that the typechecker does
 an extra validity check.

 One reason I like this restriction is that it agrees with our guiding
 principle: a library should be able to refactor what was previously a
 concrete type into an abstract one with pattern synonyms.

 Are there other opinions out there?

 And has anyone gone beyond Trac to solicit support? I've come around to
 thinking this is a good idea, but it would be nice to know that others do,
 too. Apologies if the answer to this is above -- only so many things can
 fit in my brain at once!

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10653#comment:31>
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