[GHC] #8556: Invalid constructor names are accepted in data declarations

[GHC]

#8556: Invalid constructor names are accepted in data declarations
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        Reporter:  dolio             |            Owner:
            Type:  bug               |           Status:  new
        Priority:  normal            |        Milestone:
       Component:  Compiler          |          Version:  7.6.3
      Resolution:                    |         Keywords:
Operating System:  Unknown/Multiple  |     Architecture:  Unknown/Multiple
 Type of failure:  None/Unknown      |       Difficulty:  Unknown
       Test Case:                    |       Blocked By:
        Blocking:                    |  Related Tickets:
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Comment (by monoidal):

 Here's a simple fix for 7.7 discussed on IRC:

 Writing a data declaration which contains at least one operator not
 starting with : should require -XDataKinds. So if you write `data A a =
 (&) a a` you have to enable DataKinds, since the `(&)` is available only
 in the promoted form. After KindsWithoutData get merged we will forbid it
 completely by changing the test to unconditional error.

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/8556#comment:2>
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