[GHC] #14265: kinded holes

[GHC]

#14265: kinded holes
-------------------------------------+-------------------------------------
        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:                    |
-------------------------------------+-------------------------------------
Changes (by RyanGlScott):

 * keywords:   => PartialTypeSignatures
 * component:  Compiler => Compiler (Type checker)


Comment:

 You didn't give a concrete example of what you'd like to see, so I'm
 forced to guess. My shot-in-the-dark attempt is this program:

 {{{#!hs
 {-# LANGUAGE PolyKinds #-}

 f :: proxy _ -> ()
 f _ = ()
 }}}
 {{{
 GHCi, version 8.2.1: http://www.haskell.org/ghc/  :? for help
 Loaded GHCi configuration from /home/rgscott/.ghci
 [1 of 1] Compiling Main             ( Bug.hs, interpreted )

 Bug.hs:3:12: error:
     • Found type wildcard ‘_’ standing for ‘w’
       Where: ‘w’ is a rigid type variable bound by
                the inferred type of f :: proxy w -> () at Bug.hs:4:1-8
              ‘k’ is a rigid type variable bound by
                the inferred type of f :: proxy w -> () at Bug.hs:4:1-8
       To use the inferred type, enable PartialTypeSignatures
     • In the type signature: f :: proxy _ -> ()
   |
 3 | f :: proxy _ -> ()
   |            ^
 }}}

 This output is indeed pretty skeevy-looking¸ since it points out a kind
 variable `k` in a `Where:` clause, but `k` isn't used anywhere else!
 Perhaps you wanted to see something like this instead?

 {{{
     • Found type wildcard ‘_’ standing for ‘w’ (of kind ‘k’)
       Where: ...
 }}}

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14265#comment:1>
GHC <http://www.haskell.org/ghc/>
The Glasgow Haskell Compiler