Missing trailing comma in struct causes subsequent comment to be moved

Both in relation to defining and instantiating structs, if the last field does not have a trailing comma, then rustfmt inserts one. However, if a comment is subsequently present, then it is moved up as well.

If the comma was already present, then the comment is not moved.

Before:

struct Foo {
    bar: ()
    // Comment
}

struct Bar {
    baz: ()
    /*
    Comment
    */
}

struct Baz(
    ()
    // Comment
);

fn main() {
    let _ = Foo {
        bar: ()
        /*
        Comment
        */
    };

    let _ = Bar {
        baz: ()
        /*
        Comment
        */
    };

    let _ = Baz(
        ()
        // Comment
    );
}

After:

struct Foo {
    bar: (), // Comment
}

struct Bar {
    baz: (), /*
             Comment
             */
}

struct Baz(
    (), // Comment
);

fn main() {
    let _ = Foo {
        bar: (), /*
                 Comment
                 */
    };

    let _ = Bar {
        baz: (), /*
                 Comment
                 */
    };

    let _ = Baz(
        (), // Comment
    );
}

• rustfmt 1.4.25-stable (0f29ff6d 2020-11-11)
• Tested against master (d11fde864d2369623de35a951b8a2026b7652b20)

No source file or test is named. Start by reproducing the supplied struct-definition and struct-instantiation examples with rustfmt, then trace formatting and comment handling for missing trailing commas. Done means comments remain in their original relative position while the required commas are inserted.