[GHC] #14111: strange error when using data families with levity polymorphism and unboxed sums and data families

[GHC]

#14111: strange error when using data families with levity polymorphism and unboxed
sums and data families
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        Reporter:  carter            |                Owner:  (none)
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:
       Component:  Compiler          |              Version:  8.2.1
      Resolution:                    |             Keywords:  TypeFamilies
Operating System:  Unknown/Multiple  |         Architecture:
                                     |  Unknown/Multiple
 Type of failure:  None/Unknown      |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
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Comment (by goldfire):

 I seem to recall this behavior being a deliberate design decision -- GADT
 constructor types stand alone. There was a long ticket with commentary and
 deliberations. Sadly, I can't find it, and 10 minutes of `git
 blame`-chasing in the area of code that should have been affected didn't
 find anything either. Perhaps SPJ remembers more.

 This kind of problem should always succumb to a kind annotation somewhere,
 but I agree that it's unfortunate and repetitive to put the annotation in.

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14111#comment:4>
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