Syntactic context discarded when quoting a macro invocation

[kmcallister]

#15750 is fixed now, but a variant of the same issue occurs when quoting a macro invocation.

Using plugin.rs from #15750 and this test.rs:

#![feature(phase)]

#[phase(plugin)]
extern crate plugin;

fn main() {
    let x = true;
    println!("{}", mymacro!(assert!(x)));
}

I get this result:

$ rustc -v
rustc 0.12.0-pre (3f5d0b5b6 2014-08-19 16:35:51 +0000)

$ rustc plugin.rs

$ rustc -L. test.rs
<quote expansion>:1:20: 1:21 error: unresolved name `x`.
<quote expansion>:1 name_64,ctxt_11!(x)
                                       ^
<std macros>:1:1: 12:2 note: in expansion of assert!
<quote expansion>:1:1: 1:22 note: expansion site
test.rs:1:1: 9:1 note: in expansion of mymacro!
test.rs:8:20: 8:40 note: expansion site
note: in expansion of format_args!
<std macros>:2:23: 2:77 note: expansion site
<std macros>:1:1: 3:2 note: in expansion of println!
test.rs:8:5: 8:42 note: expansion site
error: aborting due to previous error

Also the NULL characters used to delimit the magic identifier string appear in the error output, which causes the error caret to appear in the wrong place.

See also #15962.

CC @pnkfelix. This is still a huge improvement from before and I think I can work around the remaining issues in html5ever. Thank you for fixing #15750 :)

[huonw]

I have a feeling this may be a dupe of #8063, but (as stated there), I don't really understand exactly what #8063 means.

[tomjakubowski]

cc moi

[pnkfelix]

I'm actually one-quarter happy to see that the hack didn't solve everything, because it gives us a motivation to fix quote_expr! the right way: #16472 . (Although if I understand the description on #8063 correctly, #16472 on its own would not suffice.)

[lambda-fairy]

I encountered this bug in a project of mine. The code that triggered it was something like quote_expr!(cx, write!($output, "{}", $expr)), which failed when expr contained an identifier.

I worked around it by factoring out the write! call, but the issue did leave me stumped for a while.