Function split_wrapper_flags 

pub fn split_wrapper_flags(occurrences: &[WrapperOccurrence]) -> WrapperFlags

What: Split the wrapper occurrences of a parse whose flag list was built as “own escape hatch first, then the caller’s flags”. &[WrapperOccurrence] borrows the occurrence list of that parse. Why: Every command module builds its list that way, so the caller’s indexes are the tokenizer’s indexes minus one.

In TS you’d write (pseudocode):

const escape = wrapper.filter(w => w.flag === 0).map(w => w.token);
const other = wrapper.filter(w => w.flag > 0).map(w => ({ flag: w.flag - 1, token: w.token }));