Double quotes in specific positions cause string formatting errors

[waruto210]

If we set max_width = 100, and a double quote in the string appears at Col 100 during the formatting process, this double quote will be moved to the next line, causing a syntax error.

fn main() {
    let value = 1;

    let ret = format!("a.string.have.double.quote.paddinggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggg\"{}\"", value);
}

After formatting, the code becomes:

fn main() {
    let value = 1;

    let ret = format!(
        "a.string.have.double.quote.\
         paddinggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggg\\
         "{}\"",
        value
    );
}

[waruto210]

@ytmimi PTAL

[ytmimi]

PTAL?

[waruto210]

PTAL?

I mean that can you please take a look？

[ytmimi]

@waruto210 what version of rustfmt are you using, and what configuration options are you setting?

[waruto210]

@waruto210 what version of rustfmt are you using, and what configuration options are you setting?

To reproduce:
rust-toolchain.toml

channel = "nightly-2024-08-25"

rust-fmttoml

max_width = 100
format_strings = true

I have also changed the toolchain to some earlier versions，such as nightly-2024-06-25, but got the same error.

[ytmimi]

You shouldn't need to update the toolchain version. rustfmt is pinned to specific nightly toolchain. The issue is most likely a bug with format_strings There's been a similar issue about not properly handling escapes posted before. I'll try to look for it later and see if they're related or if this is a duplicate.

[ytmimi]

Did some digging. This is a duplicate of #5138