GHC confused about type synonym kind with QuantifiedConstraints

{-# LANGUAGE KindSignatures, RankNTypes, ConstraintKinds, QuantifiedConstraints #-}
module Bug where
import Data.Constraint

type E (c :: * -> Constraint) = forall (a :: *). Eq a => c a

Bug.hs:5:58: error:
    • Expected a type, but ‘c a’ has kind ‘Constraint’
    • In the type ‘forall (a :: *). Eq a => c a’
      In the type declaration for ‘E’
  |
5 | type E (c :: * -> Constraint) = forall (a :: *). Eq a => c a
  |                                                          ^^^

Note that GHC accepts the program when the Eq a constraint is removed.

Trac metadata

Trac field	Value
Version	8.6.3
Type	Bug
TypeOfFailure	OtherFailure
Priority	normal
Resolution	Unresolved
Component	Compiler
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