Function write_extra 

fn write_extra<'tcx>(
    tcx: TyCtxt<'tcx>,
    write: &mut dyn Write,
    visit_op: &dyn Fn(&mut ExtraComments<'tcx>),
    options: PrettyPrintMirOptions,
) -> Result<()>

After we print the main statement, we sometimes dump extra information. There’s often a lot of little things “nuzzled up” in a statement.