Add boxed_str.as_str()

Author: kornelski

library/alloc/src/boxed.rs

@@ -647,6 +647,15 @@ impl<T, A: Allocator> Box<T, A> {
     }
 }
 
+impl<A: Allocator> Box<str, A> {
+    #[stable(feature = "box_as_str", since = "CURRENT_RUSTC_VERSION")]
+    #[inline]
+    /// Extracts a string slice containing the entire `Box<str>`.
+    pub fn as_str(&self) -> &str {
+        &*self
+    }
+}
+
 impl<T> Box<[T]> {
     /// Constructs a new boxed slice with uninitialized contents.
     ///

library/alloc/src/rc/tests.rs

@@ -448,6 +448,7 @@ fn test_from_box_str() {
     use std::string::String;
 
     let s = String::from("foo").into_boxed_str();
+    assert_eq!((&&&s).as_str(), "foo");
     let r: Rc<str> = Rc::from(s);
 
     assert_eq!(&r[..], "foo");