Inconsistent treatment of overlap between type and kind variables in type families

The following code compiles on 7.7.20121031:

type family Foo (x :: *) (y :: x)
type instance Foo Bool Int = Int

After some poking around, I discovered that GHC is treating the type variable x and the kind variable x as distinct. In core, Foo has three arguments.

The following code does not compile:

type family Bar (x :: *) :: x

The error is

    Type variable `x' used in a kind
    In the kind `x'

I can see arguments in favor of either of the above treatments (separate namespaces for type and kind variables vs. unified namespace), but the current implementation seems inconsistent to me.

Trac metadata

Trac field	Value
Version	7.7
Type	Bug
TypeOfFailure	OtherFailure
Priority	normal
Resolution	Unresolved
Component	Compiler (Type checker)
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