Auto merge of #89219 - nickkuk:str_split_once_get_unchecked, r=Mark-Simulacrum

Use get_unchecked in str::[r]split_once

This PR removes indices checking in `str::split_once` and `str::rsplit_once` methods.
This commit is contained in:
bors 2021-10-10 12:29:48 +00:00
commit 0c87288f92

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@ -1536,7 +1536,8 @@ impl str {
#[inline]
pub fn split_once<'a, P: Pattern<'a>>(&'a self, delimiter: P) -> Option<(&'a str, &'a str)> {
let (start, end) = delimiter.into_searcher(self).next_match()?;
Some((&self[..start], &self[end..]))
// SAFETY: `Searcher` is known to return valid indices.
unsafe { Some((self.get_unchecked(..start), self.get_unchecked(end..))) }
}
/// Splits the string on the last occurrence of the specified delimiter and
@ -1556,7 +1557,8 @@ impl str {
P: Pattern<'a, Searcher: ReverseSearcher<'a>>,
{
let (start, end) = delimiter.into_searcher(self).next_match_back()?;
Some((&self[..start], &self[end..]))
// SAFETY: `Searcher` is known to return valid indices.
unsafe { Some((self.get_unchecked(..start), self.get_unchecked(end..))) }
}
/// An iterator over the disjoint matches of a pattern within the given string