Core Lint error with LiberalTypeSynonyms

See main ticket #22063

{-# LANGUAGE DataKinds #-}
{-# LANGUAGE LiberalTypeSynonyms #-}
{-# LANGUAGE PolyKinds #-}
{-# OPTIONS_GHC -dcore-lint #-}
module Bug where

import Data.Kind

type KindOf (a :: k) = k

wat :: KindOf (forall (a :: ()). a)
wat = ()

$ /opt/ghc/8.6.2/bin/ghc Bug.hs
[1 of 1] Compiling Bug              ( Bug.hs, Bug.o )
*** Core Lint errors : in result of Desugar (before optimization) ***
<no location info>: warning:
    In the type ‘KindOf (forall (a :: ()). a)’
    Non-*-like kind when *-like expected: ()
    when checking the body of forall: forall (a :: ()). a
*** Offending Program ***
Rec {
$trModule :: Module
[LclIdX]
$trModule = Module (TrNameS "main"#) (TrNameS "Bug"#)

wat :: KindOf (forall (a :: ()). a)
[LclIdX]
wat = ()
end Rec }

*** End of Offense ***


<no location info>: error: 
Compilation had errors

Trac metadata

Trac field	Value
Version	8.6.2
Type	Bug
TypeOfFailure	OtherFailure
Priority	normal
Resolution	Unresolved
Component	Compiler
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