Unclear error message when using . in format string

[Alon0709]

I tried this code:

    let x = (1, 2, 3);
    println!("{x.0}",);

I expected to see this happen: printing of the value 1.

Instead, this happened: it gave the following error:

invalid format string: expected '}', found '.'
if you intended to print {, you can escape it using {{rustcClick for full compiler diagnostic

Meta

rustc --version --verbose:

1.76.0

[Noratrieb]

Only printing an identifer is supported, arbitrary expressions are not: https://rust-lang.github.io/rfcs/2795-format-args-implicit-identifiers.html

[Noratrieb]

There's more discussion about this in https://internals.rust-lang.org/t/how-to-allow-arbitrary-expressions-in-format-strings/15812 or in many other places, it's a thing that keeps coming up.

[Noratrieb]

The error message could be nicer, so I'll convert it into a diagnostics issue.