tests/source/issue-3508.rs

fn foo<F>(foo2: F)
where
    F: Fn(
          // this comment is deleted
),
{
}

fn foo_block<F>(foo2: F)
where
    F: Fn(
        /* this comment is deleted */
  ),
{
}

fn bar(
    bar2: impl Fn(
          // this comment is deleted
    ),
) {
}

fn bar_block(
    bar2: impl Fn(
        /* this comment is deleted */
    ),
) {
}