diff --git a/library/core/src/mem/maybe_uninit.rs b/library/core/src/mem/maybe_uninit.rs index b64abf68c5e..e826ec0a5e3 100644 --- a/library/core/src/mem/maybe_uninit.rs +++ b/library/core/src/mem/maybe_uninit.rs @@ -2,6 +2,7 @@ use crate::any::type_name; use crate::fmt; use crate::intrinsics; use crate::mem::ManuallyDrop; +use crate::ptr; /// A wrapper type to construct uninitialized instances of `T`. /// @@ -573,6 +574,28 @@ impl MaybeUninit { } } + /// Drops the contained value in place. + /// + /// If you have ownership of the `MaybeUninit`, it is preferable to use + /// [`assume_init`] instead, which prevents duplicating the content. + /// + /// # Safety + /// + /// Calling this when the content is not yet fully initialized causes undefined + /// behavior: it is up to the caller to guarantee that the `MaybeUninit` really + /// is in an initialized state. + /// + /// This function runs the destructor of the contained value in place. + /// Afterwards, the memory is considered uninitialized again, but remains unmodified. + /// + /// [`assume_init`]: MaybeUninit::assume_init + #[unstable(feature = "maybe_uninit_extra", issue = "63567")] + pub unsafe fn drop(&mut self) { + // SAFETY: the caller must guarantee that `self` is initialized. + // Dropping the value in place is safe if that is the case. + unsafe { ptr::drop_in_place(self.as_mut_ptr()) } + } + /// Gets a shared reference to the contained value. /// /// This can be useful when we want to access a `MaybeUninit` that has been