Rollup merge of rust-lang#113512 - vallentin:lines-doc, r=workingjubilee

Updated lines doc to include trailing carriage return note

Updated `str::lines` doc to include explicit info about (trailing) carriage returns.

Reference: rust-lang#100311

Author: fee1-dead

library/core/src/str/mod.rs

@@ -952,6 +952,10 @@ impl str {
     ///
     /// Line terminators are not included in the lines returned by the iterator.
     ///
+    /// Note that any carriage return (`\r`) not immediately followed by a
+    /// line feed (`\n`) does not split a line. These carriage returns are
+    /// thereby included in the produced lines.
+    ///
     /// The final line ending is optional. A string that ends with a final line
     /// ending will return the same lines as an otherwise identical string
     /// without a final line ending.
@@ -961,18 +965,19 @@ impl str {
     /// Basic usage:
     ///
     /// ```
-    /// let text = "foo\r\nbar\n\nbaz\n";
+    /// let text = "foo\r\nbar\n\nbaz\r";
     /// let mut lines = text.lines();
     ///
     /// assert_eq!(Some("foo"), lines.next());
     /// assert_eq!(Some("bar"), lines.next());
     /// assert_eq!(Some(""), lines.next());
-    /// assert_eq!(Some("baz"), lines.next());
+    /// // Trailing carriage return is included in the last line
+    /// assert_eq!(Some("baz\r"), lines.next());
     ///
     /// assert_eq!(None, lines.next());
     /// ```
     ///
-    /// The final line ending isn't required:
+    /// The final line does not require any ending:
     ///
     /// ```
     /// let text = "foo\nbar\n\r\nbaz";