[GHC] #15816: Visible kind applications + data family: `U :: Type' said to be of kind `k0 -> k1` in error message

[GHC]

#15816: Visible kind applications + data family: `U :: Type' said to be of kind `k0
-> k1` in error message
-------------------------------------+-------------------------------------
           Reporter:  Iceland_jack   |             Owner:  (none)
               Type:  bug            |            Status:  new
           Priority:  normal         |         Milestone:
          Component:  Compiler       |           Version:  8.6.1
           Keywords:                 |  Operating System:  Unknown/Multiple
  TypeApplications                   |
       Architecture:                 |   Type of failure:  None/Unknown
  Unknown/Multiple                   |
          Test Case:                 |        Blocked By:
           Blocking:                 |   Related Tickets:
Differential Rev(s):                 |         Wiki Page:
-------------------------------------+-------------------------------------
 Using the [https://phabricator.haskell.org/D5229 visible kind applications
 (D5229)] (#12045) patch.

 GHC erroneously calls `U :: Type` a "function" of kind `k0 -> k1` if I
 understand this right,

 {{{
 $ ghci
 GHCi, version 8.7.20181017: http://www.haskell.org/ghc/  :? for help
 Prelude> :set prompt "> "
 > import Data.Kind (Type)
 >
 > :set -XTypeFamilies
 > :set -XTypeApplications
 >
 > data family   U      :: Type
 > data instance U @Int

 <interactive>:7:1: error:
     • Cannot apply function of kind ‘k0 -> k1’
       to visible kind argument ‘Int’
     • In the data instance declaration for ‘U’
 >
 }}}

 I expect something like "Cannot apply type `U` to visible kind argument
 `Int`" or

 {{{
 > data instance U Int = MkU

 <interactive>:7:1: error:
     • Expected kind ‘* -> *’, but ‘U’ has kind ‘*’
     • In the data instance declaration for ‘U’
 >
 }}}

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/15816>
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