file!, line! and col! (and possibly module!) do the Wrong Thing.

[paulstansifer]

In the following code, the error message refers to the location of the macro calls at HERE, not NOTHERE. I think this (a) isn't what happens in C, etc., and (b) is never useful.

Fixing this should be a simple mater of getting the syntax backtrace from cx in source_util.rs and finding the topmost span, and ignoring the span that's temptingly passed in as an argument. Except that the results won't be any different until #3065 is fixed.

macro_rules! my_complex_macro {
    { } => {
        fmt!("You invoked the macro wrong! (%s:%u:%u)",
             file!(), line!(), col!()) //HERE
    }
}

fn main() {
    io::println(my_complex_macro!()); //NOT HERE
}

[paulstansifer]

Add the following to the last list of syntax extensions in the syntax extensions section in rust.md when this bug is fixed:

* `line!`, `col!`, `file!`, `module_path!` : produce a string containing the
given source location information, relative to the starting location of
expansion

[catamorphism]

Blocked by #3065, de-milestoning

[catamorphism]

Nominating for milestone 5, production-ready

[graydon]

accepted for production-ready milestone

[graydon]

I'm confused, I think #4888 fixed this. I don't understand the statement above that #3065 blocks this. Why?

[catamorphism]

@graydon -- in the original issue, @paulstansifer said "the results won't be any different until #3065 is fixed." Maybe he will see this and explain why.

[paulstansifer]

#3065 is about making sure the syntactic backtrace (in expn_info) is correctly populated in the case of new-style macros. Perhaps that has gotten fixed somewhere along the line? Unfortunately, I don't have time right now to test the relevant examples. But if the example in the body of the bug report does work, I am comfortable declaring this bug fixed, because I can't imagine it being fixed only halfway.

[pnkfelix]

I just ran the example from reported in this bug, and the emitted message points to the line with "NOT HERE":

% /tmp/ldemo
You invoked the macro wrong! (/tmp/ldemo.rs:9:12)

So I'm closing this bug.