[GHC] #8707: Kind inference fails in data instance definition

[GHC]

#8707: Kind inference fails in data instance definition
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        Reporter:  goldfire          |            Owner:  jstolarek
            Type:  bug               |           Status:  new
        Priority:  normal            |        Milestone:
       Component:  Compiler          |          Version:  7.7
      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 simonpj):

 I'm not sure of the problem here.  It's true that, even with `-fprint-
 explicit-kinds` a promoted tuple data constructor is printed without its
 kind arguments, hence
 {{{
   Data constructor ‛SFalse’ returns type ‛SingDF Bool k '('False, Ctor k)’
 }}}
 Is that bad?  When we pretty-print Core we print tuple terms without the
 type args, thus
 {{{
    ('x', True)
 rather than
    (,) Char Bool 'x' True
 }}}
 Richard, re (2) why do you say that the error message is unhelpful
 compared to 7.6?


 Jan, how did you manage to get GHC to produce this?
 {{{
   Data constructor `SFalse' returns type `SingDF
                                           Bool k ('(,) Bool (k -> *)
 'False (Ctor k))'
 }}}
 That does look wrong.  Can you explain how to reproduce it?

 Point (1) is another matter.

 Simon

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/8707#comment:4>
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