stringify! on a ty macro value produces "an interpolated type"

[chris-morgan]

Minimal test case:

macro_rules! sty(
    ($t:ty)=>(stringify!($t))
)
fn main() {
    println(sty!(~str));
}

Expected output:

~str

Actual output:

an interpolated type

[pnkfelix]

I think something similar happens for path macro values, where it then prints "an interpolated path" post-stringify.