expected _, found () in format_args macro

[y21]

This code:

fn main() {
  format_args!(
      "{}",
      match "" {
          "" => 1,
          _ => panic!(""),
      },
  );
}

has r-a report the error "expected i32, found ()" (the i32 is the type in the match arm, changing the arm to e.g. "" changes the error to "expected &str, found ()"):

But it compiles just fine.

Possibly a duplicate of #15082? I don't know what that issue implies

rust-analyzer version: rust-analyzer version: 0.3.1591-standalone

rustc version: rustc 1.73.0-nightly (da6b55cc5 2023-07-17)

relevant settings: nothing particularly worthy of mention I think

[lowr]

This is a consequence of #15248. The gist of the problem is explained by this comment. Basically, panic! expands to $crate::panicking::panic_fmt() but we're now unable to resolve $crate, because our name resolver (or anything but eager expander) cannot see that the $crate originates from the panic! macro.

An obvious workaround is not to use any macro inside format_args! or any other macros that use it internally (e.g. println!). I'm thinking of introducing a hack so that the users won't need to deal with this themselves, but it may take a while (or forever -- it's fairly hard to get eager expansions right under our incremental architecture). Sorry for the inconvenience.