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-rw-r--r--src/libcore/str/mod.rs28
1 files changed, 20 insertions, 8 deletions
diff --git a/src/libcore/str/mod.rs b/src/libcore/str/mod.rs
index ac920185636..3cb39360380 100644
--- a/src/libcore/str/mod.rs
+++ b/src/libcore/str/mod.rs
@@ -3489,6 +3489,8 @@ impl str {
     ///
     /// assert_eq!("Hello\tworld", s.trim());
     /// ```
+    #[must_use = "this returns the trimmed string as a slice, \
+                  without modifying the original"]
     #[stable(feature = "rust1", since = "1.0.0")]
     pub fn trim(&self) -> &str {
         self.trim_matches(|c: char| c.is_whitespace())
@@ -3524,6 +3526,8 @@ impl str {
     /// let s = "  עברית  ";
     /// assert!(Some('ע') == s.trim_start().chars().next());
     /// ```
+    #[must_use = "this returns the trimmed string as a new slice, \
+                  without modifying the original"]
     #[stable(feature = "trim_direction", since = "1.30.0")]
     pub fn trim_start(&self) -> &str {
         self.trim_start_matches(|c: char| c.is_whitespace())
@@ -3559,6 +3563,8 @@ impl str {
     /// let s = "  עברית  ";
     /// assert!(Some('ת') == s.trim_end().chars().rev().next());
     /// ```
+    #[must_use = "this returns the trimmed string as a new slice, \
+                  without modifying the original"]
     #[stable(feature = "trim_direction", since = "1.30.0")]
     pub fn trim_end(&self) -> &str {
         self.trim_end_matches(|c: char| c.is_whitespace())
@@ -3661,6 +3667,8 @@ impl str {
     /// ```
     /// assert_eq!("1foo1barXX".trim_matches(|c| c == '1' || c == 'X'), "foo1bar");
     /// ```
+    #[must_use = "this returns the trimmed string as a new slice, \
+                  without modifying the original"]
     #[stable(feature = "rust1", since = "1.0.0")]
     pub fn trim_matches<'a, P: Pattern<'a>>(&'a self, pat: P) -> &'a str
         where P::Searcher: DoubleEndedSearcher<'a>
@@ -3706,6 +3714,8 @@ impl str {
     /// let x: &[_] = &['1', '2'];
     /// assert_eq!("12foo1bar12".trim_start_matches(x), "foo1bar12");
     /// ```
+    #[must_use = "this returns the trimmed string as a new slice, \
+                  without modifying the original"]
     #[stable(feature = "trim_direction", since = "1.30.0")]
     pub fn trim_start_matches<'a, P: Pattern<'a>>(&'a self, pat: P) -> &'a str {
         let mut i = self.len();
@@ -3749,6 +3759,8 @@ impl str {
     /// ```
     /// assert_eq!("1fooX".trim_end_matches(|c| c == '1' || c == 'X'), "1foo");
     /// ```
+    #[must_use = "this returns the trimmed string as a new slice, \
+                  without modifying the original"]
     #[stable(feature = "trim_direction", since = "1.30.0")]
     pub fn trim_end_matches<'a, P: Pattern<'a>>(&'a self, pat: P) -> &'a str
         where P::Searcher: ReverseSearcher<'a>
@@ -3774,10 +3786,10 @@ impl str {
     ///
     /// # Text directionality
     ///
-    /// A string is a sequence of bytes. 'Left' in this context means the first
-    /// position of that byte string; for a language like Arabic or Hebrew
-    /// which are 'right to left' rather than 'left to right', this will be
-    /// the _right_ side, not the left.
+    /// A string is a sequence of bytes. `start` in this context means the first
+    /// position of that byte string; for a left-to-right language like English or
+    /// Russian, this will be left side; and for right-to-left languages like
+    /// like Arabic or Hebrew, this will be the right side.
     ///
     /// # Examples
     ///
@@ -3806,10 +3818,10 @@ impl str {
     ///
     /// # Text directionality
     ///
-    /// A string is a sequence of bytes. 'Right' in this context means the last
-    /// position of that byte string; for a language like Arabic or Hebrew
-    /// which are 'right to left' rather than 'left to right', this will be
-    /// the _left_ side, not the right.
+    /// A string is a sequence of bytes. `end` in this context means the last
+    /// position of that byte string; for a left-to-right language like English or
+    /// Russian, this will be right side; and for right-to-left languages like
+    /// like Arabic or Hebrew, this will be the left side.
     ///
     /// # Examples
     ///