diff options
| -rw-r--r-- | src/libcore/mem.rs | 29 |
1 files changed, 28 insertions, 1 deletions
diff --git a/src/libcore/mem.rs b/src/libcore/mem.rs index 3955839ac36..42f30c1dd6d 100644 --- a/src/libcore/mem.rs +++ b/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)] |