// option. This file may not be copied, modified, or distributed
// except according to those terms.
-//! The `Clone` trait for types that cannot be 'implicitly copied'
+//! The `Clone` trait for types that cannot be 'implicitly copied'.
//!
//! In Rust, some simple types are "implicitly copyable" and when you
//! assign them or pass them as arguments, the receiver will get a copy,
//! leaving the original value in place. These types do not require
//! allocation to copy and do not have finalizers (i.e. they do not
-//! contain owned boxes or implement `Drop`), so the compiler considers
+//! contain owned boxes or implement [`Drop`]), so the compiler considers
//! them cheap and safe to copy. For other types copies must be made
-//! explicitly, by convention implementing the `Clone` trait and calling
-//! the `clone` method.
-
-#![stable]
+//! explicitly, by convention implementing the [`Clone`] trait and calling
+//! the [`clone`][clone] method.
+//!
+//! [`Clone`]: trait.Clone.html
+//! [clone]: trait.Clone.html#tymethod.clone
+//! [`Drop`]: ../../std/ops/trait.Drop.html
+//!
+//! Basic usage example:
+//!
+//! ```
+//! let s = String::new(); // String type implements Clone
+//! let copy = s.clone(); // so we can clone it
+//! ```
+//!
+//! To easily implement the Clone trait, you can also use
+//! `#[derive(Clone)]`. Example:
+//!
+//! ```
+//! #[derive(Clone)] // we add the Clone trait to Morpheus struct
+//! struct Morpheus {
+//! blue_pill: f32,
+//! red_pill: i64,
+//! }
+//!
+//! fn main() {
+//! let f = Morpheus { blue_pill: 0.0, red_pill: 0 };
+//! let copy = f.clone(); // and now we can clone it!
+//! }
+//! ```
-use marker::Sized;
+#![stable(feature = "rust1", since = "1.0.0")]
-/// A common trait for cloning an object.
-#[stable]
+/// A common trait for the ability to explicitly duplicate an object.
+///
+/// Differs from [`Copy`] in that [`Copy`] is implicit and extremely inexpensive, while
+/// `Clone` is always explicit and may or may not be expensive. In order to enforce
+/// these characteristics, Rust does not allow you to reimplement [`Copy`], but you
+/// may reimplement `Clone` and run arbitrary code.
+///
+/// Since `Clone` is more general than [`Copy`], you can automatically make anything
+/// [`Copy`] be `Clone` as well.
+///
+/// ## Derivable
+///
+/// This trait can be used with `#[derive]` if all fields are `Clone`. The `derive`d
+/// implementation of [`clone()`] calls [`clone()`] on each field.
+///
+/// ## How can I implement `Clone`?
+///
+/// Types that are [`Copy`] should have a trivial implementation of `Clone`. More formally:
+/// if `T: Copy`, `x: T`, and `y: &T`, then `let x = y.clone();` is equivalent to `let x = *y;`.
+/// Manual implementations should be careful to uphold this invariant; however, unsafe code
+/// must not rely on it to ensure memory safety.
+///
+/// An example is an array holding more than 32 elements of a type that is `Clone`; the standard
+/// library only implements `Clone` up until arrays of size 32. In this case, the implementation of
+/// `Clone` cannot be `derive`d, but can be implemented as:
+///
+/// [`Copy`]: ../../std/marker/trait.Copy.html
+/// [`clone()`]: trait.Clone.html#tymethod.clone
+///
+/// ```
+/// #[derive(Copy)]
+/// struct Stats {
+/// frequencies: [i32; 100],
+/// }
+///
+/// impl Clone for Stats {
+/// fn clone(&self) -> Stats { *self }
+/// }
+/// ```
+#[stable(feature = "rust1", since = "1.0.0")]
pub trait Clone : Sized {
/// Returns a copy of the value.
- #[stable]
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// let hello = "Hello"; // &str implements Clone
+ ///
+ /// assert_eq!("Hello", hello.clone());
+ /// ```
+ #[stable(feature = "rust1", since = "1.0.0")]
fn clone(&self) -> Self;
- /// Perform copy-assignment from `source`.
+ /// Performs copy-assignment from `source`.
///
/// `a.clone_from(&b)` is equivalent to `a = b.clone()` in functionality,
/// but can be overridden to reuse the resources of `a` to avoid unnecessary
/// allocations.
#[inline(always)]
- #[unstable = "this function is rarely used"]
+ #[stable(feature = "rust1", since = "1.0.0")]
fn clone_from(&mut self, source: &Self) {
*self = source.clone()
}
}
-#[stable]
+// FIXME(aburka): these structs are used solely by #[derive] to
+// assert that every component of a type implements Clone or Copy.
+//
+// These structs should never appear in user code.
+#[doc(hidden)]
+#[allow(missing_debug_implementations)]
+#[unstable(feature = "derive_clone_copy",
+ reason = "deriving hack, should not be public",
+ issue = "0")]
+pub struct AssertParamIsClone<T: Clone + ?Sized> { _field: ::marker::PhantomData<T> }
+#[doc(hidden)]
+#[allow(missing_debug_implementations)]
+#[unstable(feature = "derive_clone_copy",
+ reason = "deriving hack, should not be public",
+ issue = "0")]
+pub struct AssertParamIsCopy<T: Copy + ?Sized> { _field: ::marker::PhantomData<T> }
+
+#[stable(feature = "rust1", since = "1.0.0")]
impl<'a, T: ?Sized> Clone for &'a T {
- /// Return a shallow copy of the reference.
+ /// Returns a shallow copy of the reference.
#[inline]
fn clone(&self) -> &'a T { *self }
}
macro_rules! clone_impl {
($t:ty) => {
- #[stable]
+ #[stable(feature = "rust1", since = "1.0.0")]
impl Clone for $t {
- /// Return a deep copy of the value.
+ /// Returns a deep copy of the value.
#[inline]
fn clone(&self) -> $t { *self }
}
}
}
-clone_impl! { int }
+clone_impl! { isize }
clone_impl! { i8 }
clone_impl! { i16 }
clone_impl! { i32 }
clone_impl! { i64 }
+clone_impl! { i128 }
-clone_impl! { uint }
+clone_impl! { usize }
clone_impl! { u8 }
clone_impl! { u16 }
clone_impl! { u32 }
clone_impl! { u64 }
+clone_impl! { u128 }
clone_impl! { f32 }
clone_impl! { f64 }
clone_impl! { () }
clone_impl! { bool }
clone_impl! { char }
-
-macro_rules! extern_fn_clone {
- ($($A:ident),*) => (
- #[unstable = "this may not be sufficient for fns with region parameters"]
- impl<$($A,)* ReturnType> Clone for extern "Rust" fn($($A),*) -> ReturnType {
- /// Return a copy of a function pointer
- #[inline]
- fn clone(&self) -> extern "Rust" fn($($A),*) -> ReturnType { *self }
- }
- )
-}
-
-extern_fn_clone! {}
-extern_fn_clone! { A }
-extern_fn_clone! { A, B }
-extern_fn_clone! { A, B, C }
-extern_fn_clone! { A, B, C, D }
-extern_fn_clone! { A, B, C, D, E }
-extern_fn_clone! { A, B, C, D, E, F }
-extern_fn_clone! { A, B, C, D, E, F, G }
-extern_fn_clone! { A, B, C, D, E, F, G, H }
projects / rustc.git / blobdiff