Auto merge of rust-lang#138537 - yotamofek:pr/lib/multi-char-pattern, r=jhpratt

Optimize multi-char string patterns

Uses specialization for `[T]::contains` from rust-lang#130991 to optimize multi-char patterns in string searches.
Requesting a perf run to see if this actually has an effect 🙏
(I think that adding `char` to the list of types for which the `SliceContains` is specialized is a good idea, even if it doesn't show up on perf - might be helpful for downstream users)

Author: bors

library/core/src/slice/cmp.rs

@@ -282,4 +282,4 @@ macro_rules! impl_slice_contains {
     };
 }
 
-impl_slice_contains!(u16, u32, u64, i16, i32, i64, f32, f64, usize, isize);
+impl_slice_contains!(u16, u32, u64, i16, i32, i64, f32, f64, usize, isize, char);

library/core/src/str/pattern.rs

@@ -644,21 +644,21 @@ where
 impl<const N: usize> MultiCharEq for [char; N] {
     #[inline]
     fn matches(&mut self, c: char) -> bool {
-        self.iter().any(|&m| m == c)
+        self.contains(&c)
     }
 }
 
 impl<const N: usize> MultiCharEq for &[char; N] {
     #[inline]
     fn matches(&mut self, c: char) -> bool {
-        self.iter().any(|&m| m == c)
+        self.contains(&c)
     }
 }
 
 impl MultiCharEq for &[char] {
     #[inline]
     fn matches(&mut self, c: char) -> bool {
-        self.iter().any(|&m| m == c)
+        self.contains(&c)
     }
 }