[GHC] #10027: Importing constructor of associated data type fails

[GHC]

#10027: Importing constructor of associated data type fails
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        Reporter:  lspitzner         |                   Owner:
            Type:  bug               |                  Status:  new
        Priority:  normal            |               Milestone:
       Component:  Compiler          |                 Version:  7.8.4
      Resolution:                    |                Keywords:
Operating System:  Unknown/Multiple  |  constructor import associated data
 Type of failure:  None/Unknown      |  type
      Blocked By:                    |            Architecture:
 Related Tickets:                    |  Unknown/Multiple
                                     |               Test Case:
                                     |                Blocking:
                                     |  Differential Revisions:
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Comment (by goldfire):

 Don't we already have a herald for data constructors? I thought it was
 spelled `pattern`. I'm not being cheeky -- I seem to recall a proposal
 (current status/location unknown to me -- do you know?) to allow direct
 export/import of data constructors without their types via the `pattern`
 herald. That would seem to cover this case nicely, and this could be a
 motivating example for that proposal.

 With the `pattern` proposal implemented, I have only mild support for
 Simon's suggestion of exporting the data family along with any data
 instances. Would this carry over to type families too (I vote: no)? What
 if a module declares a constructor-less data instance? Does that by itself
 provoke re-export of the data family?

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10027#comment:2>
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