Enabling PolyKinds makes some type errors weird

Consider this program:

{-# LANGUAGE DataKinds #-}
{-# LANGUAGE PolyKinds #-}

module Existential where

data Any (f :: k -> *)

data X a
data Y (a :: *)
data Z (a :: Bool)

x :: Any X -> ()
x 'c' = ()

y :: Any Y -> ()
y 'c' = ()

z :: Any Z -> ()
z 'c' = ()

x, y and z are all ill-typed, but the shapes of the type errors are different in each case. They are respectively:

    Couldn't match expected type `Any k (X k)' with actual type `Char'
    Couldn't match expected type `Any * Y' with actual type `Char'
    Couldn't match expected type `Any Bool Z' with actual type `Char'

Aren't they supposed to say just 'Any X', 'Any Y' and 'Any Z'?

Trac metadata

Trac field	Value
Version	7.6.3
Type	Bug
TypeOfFailure	OtherFailure
Priority	normal
Resolution	Unresolved
Component	Compiler (Type checker)
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