Semantic highlighting for format macros

[digama0]

The {} in println!("{}", 1) is highlighted specially, which is a very nice feature. However, it only works for some of the format-like macros:

• asm!
• assert!
• assert_eq!
• assert_ne!
• debug_assert!
• debug_assert_eq!
• debug_assert_ne!
• eprint!
• eprintln!
• format!
• format_args!
• format_args_nl!
• panic! *
• print!
• println!
• todo! *
• unimplemented! *
• unreachable!
• write!
• writeln!

Arguably, support for asm is more complicated, but it seems close enough to format_args style input in the first argument that I think that applying the usual syntax highlighting will work well enough. Here's a rust snippet containing all the macros for quick testing:

fn main() {
    asm!("mov {}, 0", out(reg) _);
    assert!(true, "{}", 1);
    assert_eq!(1, 2, "{}", 1);
    assert_ne!(1, 2, "{}", 1);
    debug_assert!(true, "{}", 1);
    debug_assert_eq!(1, 2, "{}", 1);
    debug_assert_ne!(1, 2, "{}", 1);
    eprint!("{}", 1);
    eprintln!("{}", 1);
    format!("{}", 1);
    format_args!("{}", 1);
    format_args_nl!("{}", 1);
    panic!("{}", 1);
    print!("{}", 1);
    println!("{}", 1);
    todo!("{}", 1);
    unimplemented!("{}", 1);
    unreachable!("{}", 1);
    write!((), "{}", 1);
    writeln!((), "{}", 1);
}

Tested on rust-analyzer v0.2.760 on VSCode with rustc 1.57.0-nightly (11491938f 2021-09-29). The macros marked with * are recent regressions, which work on stable but not on the latest nightly, presumably due to a change in the implementation of panic! relating to rust 2021.

[jonas-schievink]

#10397 fixes panic!, assert! and debug_assert!

[jonas-schievink]

todo! and unimplemented! both expand to

$crate::panic!("not (yet) implemented: {}", $crate::format_args!($($arg)+))

which we should already handle, so there's another bug in there.

unreachable! on the other hand expands to

$crate::panic!($crate::concat!("internal error: entered unreachable code: ", $fmt), $($arg)*)

which is hard to handle correctly, since the actual format string passed to (const_)format_args! differs from the one the user sees

[jonas-schievink]

#10412 highlights asm! as a format string (note that there's also #6031 for actual assembly syntax highlighting)