Certain match expressions are unnecessarily indented and placed on next line

[taylordotfish]

Summary

I tried to format this code:

fn main() {
    let x = match y {
        z => Some(z.checked_add(1).expect(
            "1234567890123456789012345678901234567890123456789012345678901234567890123",
        )),
    };
}

Expected behavior

I expected the code to stay the same, because none of the lines exceed the length limit of 100.

Actual behavior

Instead, Rustfmt formats the code like this:

fn main() {
    let x =
        match y {
            z => Some(z.checked_add(1).expect(
                "1234567890123456789012345678901234567890123456789012345678901234567890123",
            )),
        };
}

The only difference compared to the input is that the match expression has been indented and placed on the next line. I think this is clearly worse than the input.

Configuration

Default configuration (blank rustfmt.toml).

Reproduction Steps

Run rustfmt on the sample code with default options.

Meta

rustfmt --version:

rustfmt 1.9.0-nightly (e8e4541ff1 2026-04-15)

[jieyouxu]

Triage: probably falls under the general class of #3863