Explicitly quantifying a kind variable causes a telescope to fail to kind-check

Consider the following program:

{-# LANGUAGE TypeFamilies #-}
{-# LANGUAGE TypeInType #-}
{-# LANGUAGE TypeOperators #-}
{-# OPTIONS_GHC -fprint-explicit-kinds #-}
module Bug where

import Data.Kind
import Data.Type.Equality

type family Foo1 (e :: (a :: k) :~: (a :: k)) :: Type where
  Foo1 (e :: a :~: a) = a :~: a

type family Foo2 (k :: Type) (e :: (a :: k) :~: (a :: k)) :: Type where
  Foo2 k (e :: a :~: a) = a :~: a

Foo2 is wholly equivalent to Foo1, except that in Foo2, the k kind variable is explicitly quantified. However, Foo1 typechecks, but Foo2 does not!

$ /opt/ghc/8.2.2/bin/ghci Bug.hs -fprint-explicit-kinds
GHCi, version 8.2.2: http://www.haskell.org/ghc/  :? for help
Loaded GHCi configuration from /home/ryanglscott/.ghci
[1 of 1] Compiling Bug              ( Bug.hs, interpreted )

Bug.hs:13:10: error:
    • Couldn't match kind ‘k’ with ‘k1’
      When matching the kind of ‘a’
      Expected kind ‘(:~:) k a a’, but ‘e’ has kind ‘(:~:) k a a’
    • In the second argument of ‘Foo2’, namely ‘(e :: a :~: a)’
      In the type family declaration for ‘Foo2’
   |
13 |   Foo2 k (e :: a :~: a) = a :~: a
   |          ^^^^^^^^^^^^^^

(Moreover, there seems to be a tidying bug, since GHC claims that (:~:) k a a is not the same kind as (:~:) k a a.)

Trac metadata

Trac field	Value
Version	8.2.2
Type	Bug
TypeOfFailure	OtherFailure
Priority	normal
Resolution	Unresolved
Component	Compiler (Type checker)
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