Incorrect error message when compiling with PolyKinds and a type family

When trying to compile

{-# LANGUAGE TypeFamilies,
             PolyKinds,
             ScopedTypeVariables
 #-}

convert :: a -> b
convert = undefined

type family Foo a

bar :: forall b a. b -> (Foo a)
bar f = (convert f :: (Foo a))

I get the following error message:

Sandbox.hs:12:10:
    Couldn't match type `Foo k a' with `Foo * b'
    NB: `Foo' is a type function, and may not be injective
    In the expression: (convert f :: Foo a)
    In an equation for `bar': bar f = (convert f :: Foo a)

However, this compiles just fine without PolyKinds.

Trac metadata

Trac field	Value
Version	7.4.1-rc1
Type	Bug
TypeOfFailure	OtherFailure
Priority	normal
Resolution	Unresolved
Component	Compiler (Type checker)
Test case
Differential revisions
BlockedBy
Related
Blocking
CC
Operating system
Architecture