librustc: Don't allow use after move of implicitly coerced object. Fixes #11481.

src/test/compile-fail/use-after-move-implicity-coerced-object.rs

@@ -0,0 +1,37 @@
+// Copyright 2014 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.
+
+struct Number {
+    n: i64
+}
+
+impl ToStr for Number {
+    fn to_str(&self) -> ~str {
+        self.n.to_str()
+    }
+}
+
+struct List {
+    list: ~[~ToStr]
+}
+
+impl List {
+    fn push(&mut self, n: ~ToStr) {
+        self.list.push(n);
+    }
+}
+
+fn main() {
+    let n = ~Number { n: 42 };
+    let mut l = ~List { list: ~[] };
+    l.push(n);
+    //^~ NOTE: `n` moved here because it has type `~Number`, which is non-copyable (perhaps you meant to use clone()?)
+    let x = n.to_str(); //~ ERROR: use of moved value: `n`
+}