Function promotes_to_month_end 

fn promotes_to_month_end(maturity: NaiveDate, end_of_month: bool) -> bool

Advance date by months, clamping into a short month.

Panics

If the date’s month or the shifted remainder does not fit — neither can happen for a NaiveDate. Whether a grid anchored on maturity promotes its boundaries to the calendar month end: the flag is set and the maturity is the last day of its month. Evaluated once, from the maturity, never from an interior date.