An unused output of some macros in std (e.g., format!()) should produce a unused_must_use warning.

[theemathas]

Code

fn main() {
    format!("{}", 1);
}

Current output

No errors or warnings

Desired output

warning: unused return value of `format!()` that must be used

Rationale and extra context

The format!() macro could probably expand to code containing std::hint::must_use.

List of macros with similar issues:

• cfg!()
• column!(), line!(), file!(), module_path!()
• concat!(), stringify!()
• env!(), option_env!()
• format!(), format_args!()
• include_bytes!(), include_str!()
• matches!()
• vec!()
• pin::pin!()

Other cases

No response

Rust Version

Nightly rust on playground: 1.81.0-nightly (2024-06-13 f1586001ace26df7cafe)

Anything else?

No response