Feature request: sticky matching without relying on slicing, so that `Match` range corresponds to unsliced string

[jedwards1211]

Describe your feature request

I want to be able to do find_at, captures_at etc, but without searching beyond the start index.

The reason I'm not happy with &Regex::new(r"^bar").find(&str[index..]) is the match range starts at 0, not at index. I want a Match whose range corresponds to the original string, not a slice.

I'm new to Rust, so maybe there's a smarter way to do this, but I'm trying to adapt a parsing approach I've used in other languages like

pub struct ParseState {
  str: String,
  idx: usize,
}

pub trait Parser {
  fn peek<'h>(&'h self, regex: &Regex) -> Option<Match<'h>>;
  fn find<'h>(&'h mut self, regex: &Regex) -> Option<Match<'h>>;
}

Where peek returns a Match if it exists at the current idx, and find does the same, but also advances the idx if found.

I've been able to use a sticky flag for this purpose in other languages. I wish I could just shift the Match range myself but Match::new is private. This is feeling pretty inconvenient. Seems like I'm going to have to go to the trouble to make some wrapper structs and implementations that apply the offset.