Undesired reformatting of comments applying to array elements.

[anforowicz]

REPRO:

$ cat fmt-comment-trouble.rs
const RLIB_CRATE_TYPES: [&str; 2] = [
    // https://doc.rust-lang.org/nightly/reference/linkage.html#r-link.lib
    // says:
    //
    //     > The purpose of this generic lib option is to generate
    //     > the “compiler recommended” style of library.
    //
    // For us this means `Rlib`.
    "lib",
    // Naturally "rlib" maps to `LibType::Rlib`.
    "rlib",
];


lukasza2 in /usr/local/google/home/lukasza/scratch
$ rustfmt --version
rustfmt 1.8.0-nightly (3ea711f17e 2025-03-09)

lukasza2 in /usr/local/google/home/lukasza/scratch
$ rustfmt fmt-comment-trouble.rs
Warning: the `fn_args_layout` option is deprecated. Use `fn_params_layout`. instead
Warning: the `version` option is deprecated. Use `style_edition` instead.

lukasza2 in /usr/local/google/home/lukasza/scratch
$ cat fmt-comment-trouble.rs
const RLIB_CRATE_TYPES: [&str; 2] = [
    // https://doc.rust-lang.org/nightly/reference/linkage.html#r-link.lib
    // says:
    //
    //     > The purpose of this generic lib option is to generate
    //     > the “compiler recommended” style of library.
    //
    // For us this means `Rlib`.
    "lib", // Naturally "rlib" maps to `LibType::Rlib`.
    "rlib",
];

EXPECTED BEHAVIOR: // Naturally "rlib" maps to LibType::Rlib. stays below "lib" and above "rlibs".

ACTUAL BEHAVIOR: The comment is no longer on a separate line - the comment got transformed into a trailing comment that seems to apply to "lib" rather than to "rlib".

[ytmimi]

Thanks for the report. I'm fairly certain this is a duplicate, but I can't find the issue right now