Quasiquoter raises unused import warnings

[sfackler]

#![feature(quote)]

extern crate syntax;

use syntax::ext::base::ExtCtxt;

#[allow(dead_code)]
fn f(cx: &mut ExtCtxt) {
    let idx = 10i;
    let _ = quote_expr!(cx, $idx);
}

fn main() {}

test.rs:10:13: 10:35 warning: unused import, #[warn(unused_imports)] on by default
test.rs:10     let _ = quote_expr!(cx, $idx);
                       ^~~~~~~~~~~~~~~~~~~~~~
note: in expansion of quote_expr!
test.rs:10:13: 10:35 note: expansion site
test.rs:10:13: 10:35 warning: unused import, #[warn(unused_imports)] on by default
test.rs:10     let _ = quote_expr!(cx, $idx);
                       ^~~~~~~~~~~~~~~~~~~~~~
note: in expansion of quote_expr!
test.rs:10:13: 10:35 note: expansion site

[sfackler]

cc @klutzy