auto merge of #13904 : pcwalton/rust/box, r=alexcrichton

r? @alexcrichton

RFC#14 

Issue #13885.

src/test/run-pass/new-box.rs

@@ -0,0 +1,41 @@
+// Copyright 2012 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.
+
+use std::owned::Box;
+
+fn f(x: Box<int>) {
+    let y: &int = x;
+    println!("{}", *x);
+    println!("{}", *y);
+}
+
+trait Trait {
+    fn printme(&self);
+}
+
+struct Struct;
+
+impl Trait for Struct {
+    fn printme(&self) {
+        println!("hello world!");
+    }
+}
+
+fn g(x: Box<Trait>) {
+    x.printme();
+    let y: &Trait = x;
+    y.printme();
+}
+
+fn main() {
+    f(box 1234);
+    g(box Struct as Box<Trait>);
+}
+