[GHC] #9838: PatternSynonyms and ConstraintKinds should not be required at the use site.

[GHC]

#9838: PatternSynonyms and ConstraintKinds should not be required at the use site.
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              Reporter:  ekmett      |            Owner:
                  Type:  feature     |           Status:  new
  request                            |        Milestone:
              Priority:  normal      |          Version:  7.8.3
             Component:  Compiler    |         Keywords:
            Resolution:              |     Architecture:  Unknown/Multiple
      Operating System:              |       Difficulty:  Unknown
  Unknown/Multiple                   |       Blocked By:
       Type of failure:              |  Related Tickets:
  None/Unknown                       |
             Test Case:              |
              Blocking:              |
Differential Revisions:              |
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Changes (by simonpj):

 * cc: cactus, goldfire (added)


Comment:

 I agree 100%.  Requiring a language extension flag at the definition but
 not the use is definitely GHC's standard policy.  (Eg overlapping
 instances.)

 I understand about pattern synonyms.  Gergo, could you look at this?

 I don't understand about constraint kinds. Can you give a concrete
 example?

 Simon

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9838#comment:1>
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