core: move Pattern et al to core::pattern module (RFC 2295)

Pattern is no longer str-specific, so move it from core::str::pattern
module to a new core::pattern module.  This introduces no changes in
behaviour or implementation.  Just moves stuff around and adjusts
documentation.

Issue: rust-lang#49802

library/alloc/src/str.rs

@@ -11,7 +11,7 @@ use core::borrow::{Borrow, BorrowMut};
 use core::iter::FusedIterator;
 use core::mem;
 use core::ptr;
-use core::str::pattern::{DoubleEndedSearcher, Pattern, ReverseSearcher, Searcher};
+use core::pattern::{DoubleEndedSearcher, Pattern, ReverseSearcher, Searcher};
 use core::unicode::conversions;
 
 use crate::borrow::ToOwned;
@@ -20,8 +20,6 @@ use crate::slice::{Concat, Join, SliceIndex};
 use crate::string::String;
 use crate::vec::Vec;
 
-#[stable(feature = "rust1", since = "1.0.0")]
-pub use core::str::pattern;
 #[stable(feature = "encode_utf16", since = "1.8.0")]
 pub use core::str::EncodeUtf16;
 #[stable(feature = "split_ascii_whitespace", since = "1.34.0")]

library/alloc/src/string.rs

@@ -57,7 +57,7 @@ use core::ops::Bound::{Excluded, Included, Unbounded};
 use core::ops::{self, Index, IndexMut, Range, RangeBounds};
 use core::ptr;
 use core::slice;
-use core::str::pattern::Pattern;
+use core::pattern::Pattern;
 #[cfg(not(no_global_oom_handling))]
 use core::str::Utf8Chunks;
 
@@ -1373,7 +1373,7 @@ impl String {
     where
         P: for<'x> Pattern<&'x str>,
     {
-        use core::str::pattern::Searcher;
+        use core::pattern::Searcher;
 
         let rejections = {
             let mut searcher = pat.into_searcher(self);

library/alloc/tests/str.rs

@@ -1856,14 +1856,14 @@ fn test_repeat() {
 }
 
 mod pattern {
-    use std::str::pattern::SearchStep::{self, Done, Match, Reject};
-    use std::str::pattern::{Pattern, ReverseSearcher, Searcher};
+    use core::pattern::SearchStep::{self, Done, Match, Reject};
+    use core::pattern::{Pattern, ReverseSearcher, Searcher};
 
     macro_rules! make_test {
         ($name:ident, $p:expr, $h:expr, [$($e:expr,)*]) => {
             #[allow(unused_imports)]
             mod $name {
-                use std::str::pattern::SearchStep::{Match, Reject};
+                use core::pattern::SearchStep::{Match, Reject};
                 use super::{cmp_search_to_vec};
                 #[test]
                 fn fwd() {
@@ -2139,7 +2139,7 @@ generate_iterator_test! {
 
 #[test]
 fn different_str_pattern_forwarding_lifetimes() {
-    use std::str::pattern::Pattern;
+    use core::pattern::Pattern;
 
     fn foo<'a, P>(p: P)
     where

library/core/src/lib.rs

@@ -357,6 +357,7 @@ pub mod sync;
 
 pub mod fmt;
 pub mod hash;
+pub mod pattern;
 pub mod slice;
 pub mod str;
 pub mod time;