rustfmt forcefully moves trailing comments to irrelevant code above (and not idempotent either)

[msrd0]

I sometimes write enums with a comment at the end saying something like "I should add foo in the future". Like

enum MyEnum {
    Bar,

    // I should add Foo
}

Unfortunately, rustfmt thinks it would be wise to reformat this into

enum MyEnum {
    Bar,
    // I should add Foo
}

Even worse, when enabling trailing_comma = "Never", I get the non-idempotent output where first it looks like above without the trailing comma, and then gets moved even further up:

enum MyEnum {
    Bar // I should add Foo
}

That formatting is very far from my original intention when writing code, and actively hinders readability as one might now ask why the comment should be related to that last enum variant. I think the behaviour should be changed so that rustfmt leaves the trailing comment with an empty newline as it is.

[ytmimi]

@msrd0 thanks for the report.

What version of rustfmt are you using?

[msrd0]

For the version with no parameters, I used play.rust-lang.org which claims to use 1.7.1-stable (2024-09-04 eeb90cd).

For the version with trailing_comma = "Never", I used rustfmt 1.7.1-nightly (5aea140 2024-08-20).

[ytmimi]

I believe this is related to https://github.com/rust-lang/rustfmt/issues/4757