src/test/run-pass/cell-does-not-clone.rs

   1 // Copyright 2014 The Rust Project Developers. See the COPYRIGHT
   2 // file at the top-level directory of this distribution and at
   3 // http://rust-lang.org/COPYRIGHT.
   4 //
   5 // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
   6 // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
   7 // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
   8 // option. This file may not be copied, modified, or distributed
   9 // except according to those terms.
  10
  11
  12 use std::cell::Cell;
  13
  14 #[derive(Copy)]
  15 struct Foo {
  16     x: isize
  17 }
  18
  19 impl Clone for Foo {
  20     fn clone(&self) -> Foo {
  21         // Using Cell in any way should never cause clone() to be
  22         // invoked -- after all, that would permit evil user code to
  23         // abuse `Cell` and trigger crashes.
  24
  25         panic!();
  26     }
  27 }
  28
  29 pub fn main() {
  30     let x = Cell::new(Foo { x: 22 });
  31     let _y = x.get();
  32     let _z = x.clone();
  33 }