Macro handle_cycle_error

macro_rules! handle_cycle_error {
    ([]) => { ... };
    ([(fatal_cycle) $($rest:tt)*]) => { ... };
    ([(cycle_stash) $($rest:tt)*]) => { ... };
    ([(cycle_delay_bug) $($rest:tt)*]) => { ... };
    ([$other:tt $($modifiers:tt)*]) => { ... };
}