[GHC] #5719: Empty tuple doesn't have kind Constraint

[GHC]

#5719: Empty tuple doesn't have kind Constraint
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    Reporter:  simonpj           |       Owner:                  
        Type:  bug               |      Status:  new             
    Priority:  normal            |   Milestone:                  
   Component:  Compiler          |     Version:  7.3             
    Keywords:                    |          Os:  Unknown/Multiple
Architecture:  Unknown/Multiple  |     Failure:  None/Unknown    
  Difficulty:  Unknown           |    Testcase:                  
   Blockedby:                    |    Blocking:                  
     Related:                    |  
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Changes (by dreixel):

 * cc: jpm@… (added)


Comment:

 I thought this was right. His example was different, he had:
 {{{
 class Functor f where
     type C f :: * -> Constraint
     type C f = ()
 }}}
 which correctly reports the kind error message you show.

 The class declaration you give compiles fine. And we are converting the
 singleton tuple from an `HsTyVar` into an `HsTupleTy` in
 [https://github.com/ghc/ghc/blob/master/compiler/typecheck/TcHsType.lhs#L345
 TcHsType]. What am I missing here?

-- 
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/5719#comment:2>
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