Function parse_number 

pub fn parse_number(formatter: &dyn Formatter, text: &str) -> Option<f64>

Typed number text in the formatter’s own separators and digits (the reference NumberField’s parseLocaleNumber): the digits, group and decimal separator are read off formatter.number(…); group separators, spaces and bidi marks drop, the decimal becomes ., −/– become -. None when empty or unreadable.