Union nom::lib::std::mem::ManuallyDrop 1.20.0[−][src]
pub union ManuallyDrop<T> { // some fields omitted }
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`. } }
Methods
impl<T> ManuallyDrop<T>
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impl<T> ManuallyDrop<T>
pub fn new(value: T) -> ManuallyDrop<T>
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pub fn new(value: T) -> ManuallyDrop<T>
Wrap a value to be manually dropped.
Examples
use std::mem::ManuallyDrop; ManuallyDrop::new(Box::new(()));
pub fn into_inner(slot: ManuallyDrop<T>) -> T
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pub fn into_inner(slot: ManuallyDrop<T>) -> T
Extract the value from the ManuallyDrop container.
Examples
use std::mem::ManuallyDrop; let x = ManuallyDrop::new(Box::new(())); let _: Box<()> = ManuallyDrop::into_inner(x);
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.
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> Clone for ManuallyDrop<T> where
T: Clone,
1.22.0[src]
impl<T> Clone for ManuallyDrop<T> where
T: Clone,
fn clone(&self) -> ManuallyDrop<T>
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fn clone(&self) -> ManuallyDrop<T>
Returns a copy of the value. Read more
fn clone_from(&mut self, source: &ManuallyDrop<T>)
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fn clone_from(&mut self, source: &ManuallyDrop<T>)
Performs copy-assignment from source
. Read more
impl<T> PartialOrd<ManuallyDrop<T>> for ManuallyDrop<T> where
T: PartialOrd<T>,
1.22.0[src]
impl<T> PartialOrd<ManuallyDrop<T>> for ManuallyDrop<T> where
T: PartialOrd<T>,
fn partial_cmp(&self, other: &ManuallyDrop<T>) -> Option<Ordering>
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fn partial_cmp(&self, other: &ManuallyDrop<T>) -> Option<Ordering>
This method returns an ordering between self
and other
values if one exists. Read more
fn lt(&self, other: &ManuallyDrop<T>) -> bool
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fn lt(&self, other: &ManuallyDrop<T>) -> bool
This method tests less than (for self
and other
) and is used by the <
operator. Read more
fn le(&self, other: &ManuallyDrop<T>) -> bool
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fn le(&self, other: &ManuallyDrop<T>) -> bool
This method tests less than or equal to (for self
and other
) and is used by the <=
operator. Read more
fn gt(&self, other: &ManuallyDrop<T>) -> bool
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fn gt(&self, other: &ManuallyDrop<T>) -> bool
This method tests greater than (for self
and other
) and is used by the >
operator. Read more
fn ge(&self, other: &ManuallyDrop<T>) -> bool
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fn ge(&self, other: &ManuallyDrop<T>) -> bool
This method tests greater than or equal to (for self
and other
) and is used by the >=
operator. Read more
impl<T> Ord for ManuallyDrop<T> where
T: Ord,
1.22.0[src]
impl<T> Ord for ManuallyDrop<T> where
T: Ord,
fn cmp(&self, other: &ManuallyDrop<T>) -> Ordering
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fn cmp(&self, other: &ManuallyDrop<T>) -> Ordering
This method returns an Ordering
between self
and other
. Read more
fn max(self, other: Self) -> Self
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fn max(self, other: Self) -> Self
Compares and returns the maximum of two values. Read more
fn min(self, other: Self) -> Self
1.21.0[src]
fn min(self, other: Self) -> Self
Compares and returns the minimum of two values. Read more
impl<T> Hash for ManuallyDrop<T> where
T: Hash,
1.22.0[src]
impl<T> Hash for ManuallyDrop<T> where
T: Hash,
fn hash<H>(&self, state: &mut H) where
H: Hasher,
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fn hash<H>(&self, state: &mut H) where
H: Hasher,
Feeds this value into the given [Hasher
]. Read more
fn hash_slice<H>(data: &[Self], state: &mut H) where
H: Hasher,
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fn hash_slice<H>(data: &[Self], state: &mut H) where
H: Hasher,
Feeds a slice of this type into the given [Hasher
]. Read more
impl<T> Copy for ManuallyDrop<T> where
T: Copy,
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impl<T> Copy for ManuallyDrop<T> where
T: Copy,
impl<T> Eq for ManuallyDrop<T> where
T: Eq,
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impl<T> Eq for ManuallyDrop<T> where
T: Eq,
impl<T> PartialEq<ManuallyDrop<T>> for ManuallyDrop<T> where
T: PartialEq<T>,
1.22.0[src]
impl<T> PartialEq<ManuallyDrop<T>> for ManuallyDrop<T> where
T: PartialEq<T>,
fn eq(&self, other: &ManuallyDrop<T>) -> bool
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fn eq(&self, other: &ManuallyDrop<T>) -> bool
This method tests for self
and other
values to be equal, and is used by ==
. Read more
fn ne(&self, other: &ManuallyDrop<T>) -> bool
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fn ne(&self, other: &ManuallyDrop<T>) -> bool
This method tests for !=
.
impl<T> DerefMut for ManuallyDrop<T>
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impl<T> DerefMut for ManuallyDrop<T>
fn deref_mut(&mut self) -> &mut <ManuallyDrop<T> as Deref>::Target
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fn deref_mut(&mut self) -> &mut <ManuallyDrop<T> as Deref>::Target
Mutably dereferences the value.
impl<T> Deref for ManuallyDrop<T>
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impl<T> Deref for ManuallyDrop<T>
type Target = T
The resulting type after dereferencing.
fn deref(&self) -> &<ManuallyDrop<T> as Deref>::Target
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fn deref(&self) -> &<ManuallyDrop<T> as Deref>::Target
Dereferences the value.
impl<T> Default for ManuallyDrop<T> where
T: Default,
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impl<T> Default for ManuallyDrop<T> where
T: Default,
fn default() -> ManuallyDrop<T>
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fn default() -> ManuallyDrop<T>
Returns the "default value" for a type. Read more
impl<T> Debug for ManuallyDrop<T> where
T: Debug,
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impl<T> Debug for ManuallyDrop<T> where
T: Debug,
Auto Trait Implementations
impl<T> Send for ManuallyDrop<T> where
T: Send,
impl<T> Send for ManuallyDrop<T> where
T: Send,
impl<T> Sync for ManuallyDrop<T> where
T: Sync,
impl<T> Sync for ManuallyDrop<T> where
T: Sync,