Regression error: Kind variables don't work inside of kind constructors in type families

Many thanks for the quick bug fixes around kind variables recently.

With the newest build (7.5.20120425), the following code fails:

{-# LANGUAGE PolyKinds, DataKinds, TypeFamilies, KindSignatures #-}

type family Foo (a :: k) :: Maybe k
type instance Foo a = Just a

The error is:

    Kind mis-match
    The first argument of `Just' should have kind `k0',
    but `a' has kind `k'
    In the type `Just a'
    In the type instance declaration for `Foo'

The above code compiles without error on, e.g., 7.5.20120329.

I think it's worth noting that the following compiles fine, which surprised me given the error above:

type family Id (a :: k) :: k
type instance Id a = a

Trac metadata

Trac field	Value
Version	7.5
Type	Bug
TypeOfFailure	OtherFailure
Priority	normal
Resolution	Unresolved
Component	Compiler (Type checker)
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