1.20.0[−][src]Struct std::mem::ManuallyDrop
A wrapper to inhibit compiler from automatically calling T
’s destructor.
This wrapper is 0-cost.
Examples
This wrapper helps with explicitly documenting the drop order dependencies between fields of the type:
use std::mem::ManuallyDrop; struct Peach; struct Banana; struct Melon; struct FruitBox { // Immediately clear there’s something non-trivial going on with these fields. peach: ManuallyDrop<Peach>, melon: Melon, // Field that’s independent of the other two. banana: ManuallyDrop<Banana>, } impl Drop for FruitBox { fn drop(&mut self) { unsafe { // Explicit ordering in which field destructors are run specified in the intuitive // location – the destructor of the structure containing the fields. // Moreover, one can now reorder fields within the struct however much they want. ManuallyDrop::drop(&mut self.peach); ManuallyDrop::drop(&mut self.banana); } // After destructor for `FruitBox` runs (this function), the destructor for Melon gets // invoked in the usual manner, as it is not wrapped in `ManuallyDrop`. } }Run
Methods
impl<T> ManuallyDrop<T>
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impl<T> ManuallyDrop<T>
pub const fn new(value: T) -> ManuallyDrop<T>
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pub const fn new(value: T) -> ManuallyDrop<T>
Wrap a value to be manually dropped.
Examples
use std::mem::ManuallyDrop; ManuallyDrop::new(Box::new(()));Run
pub fn into_inner(slot: ManuallyDrop<T>) -> T
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pub fn into_inner(slot: ManuallyDrop<T>) -> T
impl<T> ManuallyDrop<T> where
T: ?Sized,
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impl<T> ManuallyDrop<T> where
T: ?Sized,
pub unsafe fn drop(slot: &mut ManuallyDrop<T>)
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pub unsafe fn drop(slot: &mut ManuallyDrop<T>)
Manually drops the contained value.
If you have ownership of the value, you can use ManuallyDrop::into_inner
instead.
Safety
This function runs the destructor of the contained value and thus the wrapped value now represents uninitialized data. It is up to the user of this method to ensure the uninitialized data is not actually used.
Trait Implementations
impl<T> DerefMut for ManuallyDrop<T> where
T: ?Sized,
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impl<T> DerefMut for ManuallyDrop<T> where
T: ?Sized,
impl<T> Default for ManuallyDrop<T> where
T: Default + ?Sized,
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impl<T> Default for ManuallyDrop<T> where
T: Default + ?Sized,
impl<T> Hash for ManuallyDrop<T> where
T: Hash + ?Sized,
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impl<T> Hash for ManuallyDrop<T> where
T: Hash + ?Sized,
impl<T> Deref for ManuallyDrop<T> where
T: ?Sized,
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impl<T> Deref for ManuallyDrop<T> where
T: ?Sized,
impl<T> Debug for ManuallyDrop<T> where
T: Debug + ?Sized,
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impl<T> Debug for ManuallyDrop<T> where
T: Debug + ?Sized,
impl<T> Clone for ManuallyDrop<T> where
T: Clone + ?Sized,
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impl<T> Clone for ManuallyDrop<T> where
T: Clone + ?Sized,
impl<T> PartialOrd<ManuallyDrop<T>> for ManuallyDrop<T> where
T: PartialOrd<T> + ?Sized,
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impl<T> PartialOrd<ManuallyDrop<T>> for ManuallyDrop<T> where
T: PartialOrd<T> + ?Sized,
impl<T> Ord for ManuallyDrop<T> where
T: Ord + ?Sized,
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impl<T> Ord for ManuallyDrop<T> where
T: Ord + ?Sized,
impl<T> Eq for ManuallyDrop<T> where
T: Eq + ?Sized,
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impl<T> Eq for ManuallyDrop<T> where
T: Eq + ?Sized,
impl<T> PartialEq<ManuallyDrop<T>> for ManuallyDrop<T> where
T: PartialEq<T> + ?Sized,
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impl<T> PartialEq<ManuallyDrop<T>> for ManuallyDrop<T> where
T: PartialEq<T> + ?Sized,
impl<T> Copy for ManuallyDrop<T> where
T: Copy + ?Sized,
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impl<T> Copy for ManuallyDrop<T> where
T: Copy + ?Sized,
Auto Trait Implementations
impl<T: ?Sized> Send for ManuallyDrop<T> where
T: Send,
impl<T: ?Sized> Send for ManuallyDrop<T> where
T: Send,
impl<T: ?Sized> Sync for ManuallyDrop<T> where
T: Sync,
impl<T: ?Sized> Sync for ManuallyDrop<T> where
T: Sync,
Blanket Implementations
impl<T, U> TryFrom for T where
T: From<U>,
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impl<T, U> TryFrom for T where
T: From<U>,
type Error = !
The type returned in the event of a conversion error.
fn try_from(value: U) -> Result<T, <T as TryFrom<U>>::Error>
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fn try_from(value: U) -> Result<T, <T as TryFrom<U>>::Error>
Performs the conversion.
impl<T> From for T
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impl<T> From for T
impl<T, U> TryInto for T where
U: TryFrom<T>,
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impl<T, U> TryInto for T where
U: TryFrom<T>,
type Error = <U as TryFrom<T>>::Error
The type returned in the event of a conversion error.
fn try_into(self) -> Result<U, <U as TryFrom<T>>::Error>
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fn try_into(self) -> Result<U, <U as TryFrom<T>>::Error>
Performs the conversion.
impl<T, U> Into for T where
U: From<T>,
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impl<T, U> Into for T where
U: From<T>,
impl<T> Borrow for T where
T: ?Sized,
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impl<T> Borrow for T where
T: ?Sized,
ⓘImportant traits for &'a mut Ifn borrow(&self) -> &T
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fn borrow(&self) -> &T
Immutably borrows from an owned value. Read more
impl<T> BorrowMut for T where
T: ?Sized,
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impl<T> BorrowMut for T where
T: ?Sized,
ⓘImportant traits for &'a mut Ifn borrow_mut(&mut self) -> &mut T
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fn borrow_mut(&mut self) -> &mut T
Mutably borrows from an owned value. Read more
impl<T> Any for T where
T: 'static + ?Sized,
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impl<T> Any for T where
T: 'static + ?Sized,
fn get_type_id(&self) -> TypeId
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fn get_type_id(&self) -> TypeId
🔬 This is a nightly-only experimental API. (get_type_id
#27745)
this method will likely be replaced by an associated static
Gets the TypeId
of self
. Read more
impl<T> ToOwned for T where
T: Clone,
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impl<T> ToOwned for T where
T: Clone,
type Owned = T
fn to_owned(&self) -> T
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fn to_owned(&self) -> T
Creates owned data from borrowed data, usually by cloning. Read more
fn clone_into(&self, target: &mut T)
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fn clone_into(&self, target: &mut T)
🔬 This is a nightly-only experimental API. (toowned_clone_into
#41263)
recently added
Uses borrowed data to replace owned data, usually by cloning. Read more