Implement strip_circumfix lib feature

library/core/src/slice/mod.rs

@@ -2725,6 +2725,38 @@ impl<T> [T] {
         None
     }
 
+    /// Returns a subslice with the prefix and suffix removed.
+    ///
+    /// If the slice starts with `prefix` and ends with `suffix`, returns the subslice after the
+    /// prefix and before the suffix, wrapped in `Some`.
+    ///
+    /// If the slice does not start with `prefix` or does not end with `suffix`, returns `None`.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// #![feature(strip_circumfix)]
+    ///
+    /// let v = &[10, 50, 40, 30];
+    /// assert_eq!(v.strip_circumfix(&[10], &[30]), Some(&[50, 40][..]));
+    /// assert_eq!(v.strip_circumfix(&[10], &[40, 30]), Some(&[50][..]));
+    /// assert_eq!(v.strip_circumfix(&[10, 50], &[40, 30]), Some(&[][..]));
+    /// assert_eq!(v.strip_circumfix(&[50], &[30]), None);
+    /// assert_eq!(v.strip_circumfix(&[10], &[40]), None);
+    /// assert_eq!(v.strip_circumfix(&[], &[40, 30]), Some(&[10, 50][..]));
+    /// assert_eq!(v.strip_circumfix(&[10, 50], &[]), Some(&[40, 30][..]));
+    /// ```
+    #[must_use = "returns the subslice without modifying the original"]
+    #[unstable(feature = "strip_circumfix", issue = "147946")]
+    pub fn strip_circumfix<S, P>(&self, prefix: &P, suffix: &S) -> Option<&[T]>
+    where
+        T: PartialEq,
+        S: SlicePattern<Item = T> + ?Sized,
+        P: SlicePattern<Item = T> + ?Sized,
+    {
+        self.strip_prefix(prefix)?.strip_suffix(suffix)
+    }
+
     /// Returns a subslice with the optional prefix removed.
     ///
     /// If the slice starts with `prefix`, returns the subslice after the prefix.  If `prefix`

library/core/src/str/mod.rs

@@ -2447,6 +2447,42 @@ impl str {
         suffix.strip_suffix_of(self)
     }
 
+    /// Returns a string slice with the prefix and suffix removed.
+    ///
+    /// If the string starts with the pattern `prefix` and ends with the pattern `suffix`, returns
+    /// the substring after the prefix and before the suffix, wrapped in `Some`.
+    /// Unlike [`trim_start_matches`] and [`trim_end_matches`], this method removes both the prefix
+    /// and suffix exactly once.
+    ///
+    /// If the string does not start with `prefix` or does not end with `suffix`, returns `None`.
+    ///
+    /// Each [pattern] can be a `&str`, [`char`], a slice of [`char`]s, or a
+    /// function or closure that determines if a character matches.
+    ///
+    /// [`char`]: prim@char
+    /// [pattern]: self::pattern
+    /// [`trim_start_matches`]: Self::trim_start_matches
+    /// [`trim_end_matches`]: Self::trim_end_matches
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// #![feature(strip_circumfix)]
+    ///
+    /// assert_eq!("bar:hello:foo".strip_circumfix("bar:", ":foo"), Some("hello"));
+    /// assert_eq!("bar:foo".strip_circumfix("foo", "foo"), None);
+    /// assert_eq!("foo:bar;".strip_circumfix("foo:", ';'), Some("bar"));
+    /// ```
+    #[must_use = "this returns the remaining substring as a new slice, \
+                  without modifying the original"]
+    #[unstable(feature = "strip_circumfix", issue = "147946")]
+    pub fn strip_circumfix<P: Pattern, S: Pattern>(&self, prefix: P, suffix: S) -> Option<&str>
+    where
+        for<'a> S::Searcher<'a>: ReverseSearcher<'a>,
+    {
+        self.strip_prefix(prefix)?.strip_suffix(suffix)
+    }
+
     /// Returns a string slice with the optional prefix removed.
     ///
     /// If the string starts with the pattern `prefix`, returns the substring after the prefix.