1 // Copyright 2012-2013 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.
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.
11 //! The `Clone` trait for types that cannot be 'implicitly copied'
13 //! In Rust, some simple types are "implicitly copyable" and when you
14 //! assign them or pass them as arguments, the receiver will get a copy,
15 //! leaving the original value in place. These types do not require
16 //! allocation to copy and do not have finalizers (i.e. they do not
17 //! contain owned boxes or implement `Drop`), so the compiler considers
18 //! them cheap and safe to copy. For other types copies must be made
19 //! explicitly, by convention implementing the `Clone` trait and calling
20 //! the `clone` method.
26 /// A common trait for cloning an object.
28 pub trait Clone : Sized {
29 /// Returns a copy of the value.
31 fn clone(&self) -> Self;
33 /// Perform copy-assignment from `source`.
35 /// `a.clone_from(&b)` is equivalent to `a = b.clone()` in functionality,
36 /// but can be overridden to reuse the resources of `a` to avoid unnecessary
39 #[unstable = "this function is rarely used"]
40 fn clone_from(&mut self, source: &Self) {
41 *self = source.clone()
46 impl<'a, T: ?Sized> Clone for &'a T {
47 /// Return a shallow copy of the reference.
49 fn clone(&self) -> &'a T { *self }
52 macro_rules! clone_impl {
56 /// Return a deep copy of the value.
58 fn clone(&self) -> $t { *self }
82 macro_rules! extern_fn_clone {
84 #[experimental = "this may not be sufficient for fns with region parameters"]
85 impl<$($A,)* ReturnType> Clone for extern "Rust" fn($($A),*) -> ReturnType {
86 /// Return a copy of a function pointer
88 fn clone(&self) -> extern "Rust" fn($($A),*) -> ReturnType { *self }
94 extern_fn_clone! { A }
95 extern_fn_clone! { A, B }
96 extern_fn_clone! { A, B, C }
97 extern_fn_clone! { A, B, C, D }
98 extern_fn_clone! { A, B, C, D, E }
99 extern_fn_clone! { A, B, C, D, E, F }
100 extern_fn_clone! { A, B, C, D, E, F, G }
101 extern_fn_clone! { A, B, C, D, E, F, G, H }