version Two no longer able to format code

fn f() {}

fn main() {
    f(0, 1,);        // f()
    //~^ error: this function takes 0 arguments but 2 arguments were supplied
}

with version = "Two"
it looks like rustfmt does no longer know that the comment on line 5 exists, it thus flags " " as

error[internal]: left behind trailing whitespace
 --> /tmp/im/a.rs:5:5:1
  |
5 |
  | ^^^^
  |

which it isnt because there is a comment after the indentation (unless it tries to remove the entire comment which is spooky as well)

Start by running rustfmt with version = "Two" on the Rust snippet in the issue and observe the reported trailing whitespace at the commented argument line. Trace how rustfmt handles that line and its comment; done means the code formats without falsely reporting indentation as trailing whitespace while preserving the comment.