[GHC] #14265: kinded holes

[GHC]

#14265: kinded holes
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        Reporter:  lspitzner         |                Owner:  (none)
            Type:  feature request   |               Status:  new
        Priority:  normal            |            Milestone:
       Component:  Compiler (Type    |              Version:  8.2.1
  checker)                           |             Keywords:
      Resolution:                    |  PartialTypeSignatures
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 lspitzner):

 That is exactly what I meant. Polykinded was not even in my mind; it would
 not hurt to have the same in simpler (non-polykind) cases too, like

 {{{#!hs
 foo :: StateT _ _ (); foo = undefined
 }}}

 could produce

 {{{
 <interactive>:7:15: error:
     • Found type wildcard ‘_’ standing for ‘w’ (of kind ‘*’)
       Where: ‘w’ is a rigid type variable bound by
                the inferred type of foo :: StateT w w1 () at
 <interactive>:7:23-37
       To use the inferred type, enable PartialTypeSignatures
     • In the type signature: foo :: StateT _ _ ()

 <interactive>:7:17: error:
     • Found type wildcard ‘_’ standing for ‘w1’ (of kind ‘* -> *’)
 …
 }}}

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14265#comment:2>
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