writeln! and println! (and builtin macros’?) diagnostics are terrible

[nagisa]

<std macros>:4:19: 4:46 error: invalid reference to argument `1` (there is 1 argument)
<std macros>:4 write ! ( $ dst , concat ! ( $ fmt , "\n" ) , $ ( $ arg ) * ) ) ;
                                 ^~~~~~~~~~~~~~~~~~~~~~~~~~~

<std macros>:3:11: 3:38 error: invalid reference to argument `2` (there are 2 arguments)
<std macros>:3 print ! ( concat ! ( $ fmt , "\n" ) , $ ( $ arg ) * ) ) ;
                         ^~~~~~~~~~~~~~~~~~~~~~~~~~~

I’d expect it to at least emit an in expansion of writeln! and in expansion of println! hints which it doesn’t currently.

[jakerr]

It also doesn't even say where the invocation is. With cargo build --verbose -j 1 I can see which file was being compiled when a macro invocation broke but I have no real idea which line it was. When there are many similar invocations in the file it can be quite painful to track down.

Here's a minimal reproduction

use std::fs::File;
use std::path::Path;
// use std::io::Write;

fn main() {
    let mut file = File::create("hello.txt").unwrap();
    write!(&mut file, "Hello, {}", "world!").unwrap();
}

Because use std::io::Write is missing we get an error message like:

<std macros>:2:20: 2:66 error: type `&mut std::fs::File` does not implement any method in scope named `write_fmt`
<std macros>:2 ( & mut * $ dst ) . write_fmt ( format_args ! ( $ ( $ arg ) * ) ) )
                                  ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
<std macros>:2:66: 2:66 help: methods from traits can only be called if the trait is in scope; the following trait is implemented but not in scope, perhaps add a `use` for it:
<std macros>:2:66: 2:66 help: candidate #1: use `std::io::Write`

Notice that it doesn't mention the file or line number of the invocation, in this case: src/main.rs:8, which means it's hard to find and breaks tools like vim's error list.

[kornelski]

👍

println!("{} {}", 1);

:3 print ! ( concat ! ( $ fmt , "\n" ) , $ ( $ arg ) * ) ) ;

[tamird]

This should have been closed by #24003 I believe