quote_expr! causes compile error when invoked twice on an ident nested in a macro invocation

[lambda-fairy]

Sorry about the long title. I couldn't find a better way to express the issue :)

Given the following syntax extension:

#![crate_type = "dylib"]
#![allow(unstable)]
#![feature(plugin_registrar, quote)]

extern crate syntax;
extern crate rustc;

use syntax::ast::TokenTree;
use syntax::codemap::Span;
use syntax::ext::base::{DummyResult, ExtCtxt, MacExpr, MacResult};
use rustc::plugin::Registry;

fn expand<'cx>(cx: &'cx mut ExtCtxt, sp: Span, args: &[TokenTree]) -> Box<MacResult + 'cx> {
    match args {
        [ref tt, ..] => {
            let e = quote_expr!(cx, println!("{}", $tt));
            MacExpr::new(quote_expr!(cx, $e))
        },
        _ => DummyResult::any(sp),
    }
}

#[plugin_registrar]
pub fn plugin_registrar(reg: &mut Registry) {
    reg.register_macro("macro_test", expand);
}

and this test file:

#![feature(plugin)]

#[plugin] #[no_link] extern crate quote_fail;

#[test]
fn it_works() {
    let a = "hello";
    macro_test!(a);
}

The latter fails to compile with the following error:

<quote expansion>:1:27: 1:28 error: unresolved name `a`
<quote expansion>:1 name_228,ctxt_0!("{}" , a)
                                              ^
note: in expansion of format_args!
<std macros>:2:42: 2:75 note: expansion site
<std macros>:1:1: 2:77 note: in expansion of println!
<quote expansion>:1:1: 1:29 note: expansion site
/home/chris/dev/quote_fail/tests/tests.rs:1:1: 9:1 note: in expansion of macro_test!
/home/chris/dev/quote_fail/tests/tests.rs:8:5: 8:20 note: expansion site
error: aborting due to previous error
Could not compile `quote_fail`.

This error goes away if I do either of these things:

• Remove the println! call, i.e. replace println!("{}", $tt) with $tt
• Call quote_expr! only once instead of twice, i.e. MacExpr::new(e)

I'm using rustc commit 8903c21 built 2015-01-16 on Ubuntu 14.10 x86_64.

[lambda-fairy]

This looks like a duplicate of #16617, so I'm closing this in favor of that.