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

Optimize multi-char string patterns
Uses specialization for `[T]::contains` from #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<constN:usize>MultiCharEqfor[char;N]{
 #[inline]
 fnmatches(&mutself,c:char) -> bool{
-self.iter().any(|&m| m == c)
+self.contains(&c)
 }
 }
 
 impl<constN:usize>MultiCharEqfor&[char;N]{
 #[inline]
 fnmatches(&mutself,c:char) -> bool{
-self.iter().any(|&m| m == c)
+self.contains(&c)
 }
 }
 
 implMultiCharEqfor&[char]{
 #[inline]
 fnmatches(&mutself,c:char) -> bool{
-self.iter().any(|&m| m == c)
+self.contains(&c)
 }
 }