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also add examples to MaybeUninit::into_initialized

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RalfJung committed Feb 22, 2019
1 parent 13ffbee commit dc570fb3f26b45d101440bb4fe57121ca06884d3
Showing with 28 additions and 1 deletion.
  1. +28 −1 src/libcore/mem.rs
@@ -1178,6 +1178,31 @@ impl<T> MaybeUninit<T> {
/// It is up to the caller to guarantee that the `MaybeUninit` really is in an initialized
/// state. Calling this when the content is not yet fully initialized causes undefined
/// behavior.
///
/// # Examples
///
/// Correct usage of this method:
///
/// ```rust
/// #![feature(maybe_uninit)]
/// use std::mem::MaybeUninit;
///
/// let mut x = MaybeUninit::<bool>::uninitialized();
/// x.set(true);
/// let x_init = unsafe { x.into_initialized() };
/// assert_eq!(x_init, true);
/// ```
///
/// *Incorrect* usage of this method:
///
/// ```rust,no_run
/// #![feature(maybe_uninit)]
/// use std::mem::MaybeUninit;
///
/// let x = MaybeUninit::<Vec<u32>>::uninitialized();
/// let x_init = unsafe { x.into_initialized() };
/// // `x` had not been initialized yet, so this last line causes undefined behavior.
/// ```
#[unstable(feature = "maybe_uninit", issue = "53491")]
#[inline(always)]
pub unsafe fn into_initialized(self) -> T {
@@ -1212,15 +1237,17 @@ impl<T> MaybeUninit<T> {
/// let x1 = unsafe { x.read_initialized() };
/// // `u32` is `Copy`, so we may read multiple times.
/// let x2 = unsafe { x.read_initialized() };
/// assert_eq!(x1, x2);
///
/// let mut x = MaybeUninit::<Option<Vec<u32>>>::uninitialized();
/// x.set(None);
/// let x1 = unsafe { x.read_initialized() };
/// // Duplicating a `None` value is okay, so we may read multiple times.
/// let x2 = unsafe { x.read_initialized() };
/// assert_eq!(x1, x2);
/// ```
///
/// *Incorrect* usafe of this method:
/// *Incorrect* usage of this method:
///
/// ```rust,no_run
/// #![feature(maybe_uninit)]

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