More methods for str boxes.

src/liballoc/str.rs

@@ -0,0 +1,21 @@
+// Copyright 2012-2017 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+//! Methods for dealing with boxed strings.
+use core::mem;
+
+use boxed::Box;
+
+/// Converts a boxed slice of bytes to a boxed string slice without checking
+/// that the string contains valid UTF-8.
+#[unstable(feature = "str_box_extras", issue = "41119")]
+pub unsafe fn from_boxed_utf8_unchecked(v: Box<[u8]>) -> Box<str> {
+    mem::transmute(v)
+}