Errors inside a macro invocation don't report the full location of the error

[erickt]

It seems the debug! code isn't properly pushing a span onto the macro expansion span stack. This code:

fn main() {
    let a = ~"";
    debug!("foo: %s %s", a);
}

Only reports the error inside the macro, but not where that macro is getting used:

<core-macros>:33:24: 33:42 error: not enough arguments to fmt! for the given format string
<core-macros>:33             __log(4u32, fmt!( $($arg),+ ))
                                         ^~~~~~~~~~~~~~~~~~

[alexcrichton]

Nominating for production-ready

[huonw]

Triage visit: still valid, but this isn't at all specific to debug! or even the built-in macros (adjusting the title):

macro_rules! my_fmt {
    ($s:expr, $($e:expr),*) => {
        fmt!($s, $($e),*)
    }
}

fn main() {
    let a = ~"";
    my_fmt!("foo: %s %s", a);
}

5794.rs:3:8: 3:25 error: not enough arguments to fmt! for the given format string
5794.rs:3         fmt!($s, $($e),*)
                  ^~~~~~~~~~~~~~~~~

It's hard to see how this would be resolved in general, since some of the time the errors will be caused by something internal to the macro (e.g. => fmt!("%s %s", $e) in a macro body); possibly putting a note on the invocation of any macros that have errors, e.g.:

macro_rules! my_fmt {
    ($s:expr, $($e:expr),*) => {
        fmt!($s, $($e),*) // error: not enough arguments to fmt! ...
    }
}

fn main() {
    let a = ~"";
    my_fmt!("foo: %s %s", a); // note: macro invoked here
}

[graydon]

accepted for production-ready milestone

[alexcrichton]

@jbclements, you were working in macros recently, do you have any idea what this would entail to fix? Right now @huonw and I are thinking that this should block #9153 because the error spans are so terrible.

[jbclements]

duplicating comment from IRC, I think it might help a lot just to include the arguments to the macro that failed.