Struct tract_nnef::internal::tract_downcast_rs::__alloc::sync::Weak 1.4.0[−][src]
pub struct Weak<T> where
T: ?Sized, { /* fields omitted */ }
Weak
is a version of Arc
that holds a non-owning reference to the
managed allocation. The allocation is accessed by calling upgrade
on the Weak
pointer, which returns an Option
<
Arc
<T>>
.
Since a Weak
reference does not count towards ownership, it will not
prevent the value stored in the allocation from being dropped, and Weak
itself makes no
guarantees about the value still being present. Thus it may return None
when upgrade
d. Note however that a Weak
reference does prevent the allocation
itself (the backing store) from being deallocated.
A Weak
pointer is useful for keeping a temporary reference to the allocation
managed by Arc
without preventing its inner value from being dropped. It is also used to
prevent circular references between Arc
pointers, since mutual owning references
would never allow either Arc
to be dropped. For example, a tree could
have strong Arc
pointers from parent nodes to children, and Weak
pointers from children back to their parents.
The typical way to obtain a Weak
pointer is to call Arc::downgrade
.
Implementations
impl<T> Weak<T>
[src]
impl<T> Weak<T> where
T: ?Sized,
[src]
T: ?Sized,
pub fn as_ptr(&self) -> *const T
1.45.0[src]
Returns a raw pointer to the object T
pointed to by this Weak<T>
.
The pointer is valid only if there are some strong references. The pointer may be dangling,
unaligned or even null
otherwise.
Examples
use std::sync::Arc; use std::ptr; let strong = Arc::new("hello".to_owned()); let weak = Arc::downgrade(&strong); // Both point to the same object assert!(ptr::eq(&*strong, weak.as_ptr())); // The strong here keeps it alive, so we can still access the object. assert_eq!("hello", unsafe { &*weak.as_ptr() }); drop(strong); // But not any more. We can do weak.as_ptr(), but accessing the pointer would lead to // undefined behaviour. // assert_eq!("hello", unsafe { &*weak.as_ptr() });
pub fn into_raw(self) -> *const T
1.45.0[src]
Consumes the Weak<T>
and turns it into a raw pointer.
This converts the weak pointer into a raw pointer, while still preserving the ownership of
one weak reference (the weak count is not modified by this operation). It can be turned
back into the Weak<T>
with from_raw
.
The same restrictions of accessing the target of the pointer as with
as_ptr
apply.
Examples
use std::sync::{Arc, Weak}; let strong = Arc::new("hello".to_owned()); let weak = Arc::downgrade(&strong); let raw = weak.into_raw(); assert_eq!(1, Arc::weak_count(&strong)); assert_eq!("hello", unsafe { &*raw }); drop(unsafe { Weak::from_raw(raw) }); assert_eq!(0, Arc::weak_count(&strong));
pub unsafe fn from_raw(ptr: *const T) -> Weak<T>
1.45.0[src]
Converts a raw pointer previously created by into_raw
back into Weak<T>
.
This can be used to safely get a strong reference (by calling upgrade
later) or to deallocate the weak count by dropping the Weak<T>
.
It takes ownership of one weak reference (with the exception of pointers created by new
,
as these don’t own anything; the method still works on them).
Safety
The pointer must have originated from the into_raw
and must still own its potential
weak reference.
It is allowed for the strong count to be 0 at the time of calling this. Nevertheless, this
takes ownership of one weak reference currently represented as a raw pointer (the weak
count is not modified by this operation) and therefore it must be paired with a previous
call to into_raw
.
Examples
use std::sync::{Arc, Weak}; let strong = Arc::new("hello".to_owned()); let raw_1 = Arc::downgrade(&strong).into_raw(); let raw_2 = Arc::downgrade(&strong).into_raw(); assert_eq!(2, Arc::weak_count(&strong)); assert_eq!("hello", &*unsafe { Weak::from_raw(raw_1) }.upgrade().unwrap()); assert_eq!(1, Arc::weak_count(&strong)); drop(strong); // Decrement the last weak count. assert!(unsafe { Weak::from_raw(raw_2) }.upgrade().is_none());
impl<T> Weak<T> where
T: ?Sized,
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T: ?Sized,
pub fn upgrade(&self) -> Option<Arc<T>>
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Attempts to upgrade the Weak
pointer to an Arc
, delaying
dropping of the inner value if successful.
Returns None
if the inner value has since been dropped.
Examples
use std::sync::Arc; let five = Arc::new(5); let weak_five = Arc::downgrade(&five); let strong_five: Option<Arc<_>> = weak_five.upgrade(); assert!(strong_five.is_some()); // Destroy all strong pointers. drop(strong_five); drop(five); assert!(weak_five.upgrade().is_none());
pub fn strong_count(&self) -> usize
1.41.0[src]
Gets the number of strong (Arc
) pointers pointing to this allocation.
If self
was created using Weak::new
, this will return 0.
pub fn weak_count(&self) -> usize
1.41.0[src]
Gets an approximation of the number of Weak
pointers pointing to this
allocation.
If self
was created using Weak::new
, or if there are no remaining
strong pointers, this will return 0.
Accuracy
Due to implementation details, the returned value can be off by 1 in
either direction when other threads are manipulating any Arc
s or
Weak
s pointing to the same allocation.
pub fn ptr_eq(&self, other: &Weak<T>) -> bool
1.39.0[src]
Returns true
if the two Weak
s point to the same allocation (similar to
ptr::eq
), or if both don’t point to any allocation
(because they were created with Weak::new()
).
Notes
Since this compares pointers it means that Weak::new()
will equal each
other, even though they don’t point to any allocation.
Examples
use std::sync::Arc; let first_rc = Arc::new(5); let first = Arc::downgrade(&first_rc); let second = Arc::downgrade(&first_rc); assert!(first.ptr_eq(&second)); let third_rc = Arc::new(5); let third = Arc::downgrade(&third_rc); assert!(!first.ptr_eq(&third));
Comparing Weak::new
.
use std::sync::{Arc, Weak}; let first = Weak::new(); let second = Weak::new(); assert!(first.ptr_eq(&second)); let third_rc = Arc::new(()); let third = Arc::downgrade(&third_rc); assert!(!first.ptr_eq(&third));
Trait Implementations
impl<T> Clone for Weak<T> where
T: ?Sized,
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T: ?Sized,
pub fn clone(&self) -> Weak<T>
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Makes a clone of the Weak
pointer that points to the same allocation.
Examples
use std::sync::{Arc, Weak}; let weak_five = Arc::downgrade(&Arc::new(5)); let _ = Weak::clone(&weak_five);
pub fn clone_from(&mut self, source: &Self)
1.0.0[src]
impl<T, U> CoerceUnsized<Weak<U>> for Weak<T> where
T: Unsize<U> + ?Sized,
U: ?Sized,
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T: Unsize<U> + ?Sized,
U: ?Sized,
impl<T> Debug for Weak<T> where
T: Debug + ?Sized,
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T: Debug + ?Sized,
impl<T> Default for Weak<T>
1.10.0[src]
impl<T, U> DispatchFromDyn<Weak<U>> for Weak<T> where
T: Unsize<U> + ?Sized,
U: ?Sized,
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T: Unsize<U> + ?Sized,
U: ?Sized,
impl<T> Drop for Weak<T> where
T: ?Sized,
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T: ?Sized,
pub fn drop(&mut self)
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Drops the Weak
pointer.
Examples
use std::sync::{Arc, Weak}; struct Foo; impl Drop for Foo { fn drop(&mut self) { println!("dropped!"); } } let foo = Arc::new(Foo); let weak_foo = Arc::downgrade(&foo); let other_weak_foo = Weak::clone(&weak_foo); drop(weak_foo); // Doesn't print anything drop(foo); // Prints "dropped!" assert!(other_weak_foo.upgrade().is_none());
impl<T> Send for Weak<T> where
T: Sync + Send + ?Sized,
[src]
T: Sync + Send + ?Sized,
impl<T> Sync for Weak<T> where
T: Sync + Send + ?Sized,
[src]
T: Sync + Send + ?Sized,
Auto Trait Implementations
impl<T: ?Sized> RefUnwindSafe for Weak<T> where
T: RefUnwindSafe,
T: RefUnwindSafe,
impl<T: ?Sized> Unpin for Weak<T>
impl<T: ?Sized> UnwindSafe for Weak<T> where
T: RefUnwindSafe,
T: RefUnwindSafe,
Blanket Implementations
impl<T> Any for T where
T: 'static + ?Sized,
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T: 'static + ?Sized,
impl<T> Borrow<T> for T where
T: ?Sized,
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T: ?Sized,
pub fn borrow(&self) -> &TⓘNotable traits for &'_ mut R
impl<'_, R> Read for &'_ mut R where
R: Read + ?Sized, impl<'_, W> Write for &'_ mut W where
W: Write + ?Sized, impl<'_, I> Iterator for &'_ mut I where
I: Iterator + ?Sized, type Item = <I as Iterator>::Item;impl<'_, F> Future for &'_ mut F where
F: Future + Unpin + ?Sized, type Output = <F as Future>::Output;
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Notable traits for &'_ mut R
impl<'_, R> Read for &'_ mut R where
R: Read + ?Sized, impl<'_, W> Write for &'_ mut W where
W: Write + ?Sized, impl<'_, I> Iterator for &'_ mut I where
I: Iterator + ?Sized, type Item = <I as Iterator>::Item;impl<'_, F> Future for &'_ mut F where
F: Future + Unpin + ?Sized, type Output = <F as Future>::Output;
impl<T> BorrowMut<T> for T where
T: ?Sized,
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T: ?Sized,
pub fn borrow_mut(&mut self) -> &mut TⓘNotable traits for &'_ mut R
impl<'_, R> Read for &'_ mut R where
R: Read + ?Sized, impl<'_, W> Write for &'_ mut W where
W: Write + ?Sized, impl<'_, I> Iterator for &'_ mut I where
I: Iterator + ?Sized, type Item = <I as Iterator>::Item;impl<'_, F> Future for &'_ mut F where
F: Future + Unpin + ?Sized, type Output = <F as Future>::Output;
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Notable traits for &'_ mut R
impl<'_, R> Read for &'_ mut R where
R: Read + ?Sized, impl<'_, W> Write for &'_ mut W where
W: Write + ?Sized, impl<'_, I> Iterator for &'_ mut I where
I: Iterator + ?Sized, type Item = <I as Iterator>::Item;impl<'_, F> Future for &'_ mut F where
F: Future + Unpin + ?Sized, type Output = <F as Future>::Output;
impl<T> Conv for T
impl<T> Conv for T
impl<T> Downcast for T where
T: Any,
T: Any,
pub fn into_any(self: Box<T, Global>) -> Box<dyn Any + 'static, Global>ⓘNotable traits for Box<R, Global>
impl<R> Read for Box<R, Global> where
R: Read + ?Sized, impl<W> Write for Box<W, Global> where
W: Write + ?Sized, impl<I, A> Iterator for Box<I, A> where
A: Allocator,
I: Iterator + ?Sized, type Item = <I as Iterator>::Item;impl<F, A> Future for Box<F, A> where
F: Future + Unpin + ?Sized,
A: Allocator + 'static, type Output = <F as Future>::Output;
Notable traits for Box<R, Global>
impl<R> Read for Box<R, Global> where
R: Read + ?Sized, impl<W> Write for Box<W, Global> where
W: Write + ?Sized, impl<I, A> Iterator for Box<I, A> where
A: Allocator,
I: Iterator + ?Sized, type Item = <I as Iterator>::Item;impl<F, A> Future for Box<F, A> where
F: Future + Unpin + ?Sized,
A: Allocator + 'static, type Output = <F as Future>::Output;
pub fn into_any_rc(self: Rc<T>) -> Rc<dyn Any + 'static>
pub fn as_any(&self) -> &(dyn Any + 'static)
pub fn as_any_mut(&mut self) -> &mut (dyn Any + 'static)
impl<T> DowncastSync for T where
T: Any + Send + Sync,
T: Any + Send + Sync,
impl<T> DynClone for T where
T: Clone,
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T: Clone,
pub fn __clone_box(&self, Private) -> *mut ()
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impl<T> FmtForward for T
pub fn fmt_binary(self) -> FmtBinary<Self> where
Self: Binary,
Self: Binary,
pub fn fmt_display(self) -> FmtDisplay<Self> where
Self: Display,
Self: Display,
pub fn fmt_lower_exp(self) -> FmtLowerExp<Self> where
Self: LowerExp,
Self: LowerExp,
pub fn fmt_lower_hex(self) -> FmtLowerHex<Self> where
Self: LowerHex,
Self: LowerHex,
pub fn fmt_octal(self) -> FmtOctal<Self> where
Self: Octal,
Self: Octal,
pub fn fmt_pointer(self) -> FmtPointer<Self> where
Self: Pointer,
Self: Pointer,
pub fn fmt_upper_exp(self) -> FmtUpperExp<Self> where
Self: UpperExp,
Self: UpperExp,
pub fn fmt_upper_hex(self) -> FmtUpperHex<Self> where
Self: UpperHex,
Self: UpperHex,
impl<T> From<T> for T
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impl<T, U> Into<U> for T where
U: From<T>,
[src]
U: From<T>,
impl<T> Pipe for T where
T: ?Sized,
T: ?Sized,
pub fn pipe<R>(self, func: impl FnOnce(Self) -> R) -> R
pub fn pipe_ref<'a, R>(&'a self, func: impl FnOnce(&'a Self) -> R) -> R where
R: 'a,
R: 'a,
pub fn pipe_ref_mut<'a, R>(
&'a mut self,
func: impl FnOnce(&'a mut Self) -> R
) -> R where
R: 'a,
&'a mut self,
func: impl FnOnce(&'a mut Self) -> R
) -> R where
R: 'a,
pub fn pipe_borrow<'a, B, R>(&'a self, func: impl FnOnce(&'a B) -> R) -> R where
Self: Borrow<B>,
R: 'a,
B: 'a + ?Sized,
Self: Borrow<B>,
R: 'a,
B: 'a + ?Sized,
pub fn pipe_borrow_mut<'a, B, R>(
&'a mut self,
func: impl FnOnce(&'a mut B) -> R
) -> R where
Self: BorrowMut<B>,
R: 'a,
B: 'a + ?Sized,
&'a mut self,
func: impl FnOnce(&'a mut B) -> R
) -> R where
Self: BorrowMut<B>,
R: 'a,
B: 'a + ?Sized,
pub fn pipe_as_ref<'a, U, R>(&'a self, func: impl FnOnce(&'a U) -> R) -> R where
Self: AsRef<U>,
R: 'a,
U: 'a + ?Sized,
Self: AsRef<U>,
R: 'a,
U: 'a + ?Sized,
pub fn pipe_as_mut<'a, U, R>(
&'a mut self,
func: impl FnOnce(&'a mut U) -> R
) -> R where
Self: AsMut<U>,
R: 'a,
U: 'a + ?Sized,
&'a mut self,
func: impl FnOnce(&'a mut U) -> R
) -> R where
Self: AsMut<U>,
R: 'a,
U: 'a + ?Sized,
pub fn pipe_deref<'a, T, R>(&'a self, func: impl FnOnce(&'a T) -> R) -> R where
Self: Deref<Target = T>,
T: 'a + ?Sized,
R: 'a,
Self: Deref<Target = T>,
T: 'a + ?Sized,
R: 'a,
pub fn pipe_deref_mut<'a, T, R>(
&'a mut self,
func: impl FnOnce(&'a mut T) -> R
) -> R where
Self: DerefMut<Target = T> + Deref,
T: 'a + ?Sized,
R: 'a,
&'a mut self,
func: impl FnOnce(&'a mut T) -> R
) -> R where
Self: DerefMut<Target = T> + Deref,
T: 'a + ?Sized,
R: 'a,
impl<T> Pipe for T
impl<T> PipeAsRef for T
pub fn pipe_as_ref<'a, T, R>(&'a self, func: impl FnOnce(&'a T) -> R) -> R where
Self: AsRef<T>,
T: 'a,
R: 'a,
Self: AsRef<T>,
T: 'a,
R: 'a,
pub fn pipe_as_mut<'a, T, R>(
&'a mut self,
func: impl FnOnce(&'a mut T) -> R
) -> R where
Self: AsMut<T>,
T: 'a,
R: 'a,
&'a mut self,
func: impl FnOnce(&'a mut T) -> R
) -> R where
Self: AsMut<T>,
T: 'a,
R: 'a,
impl<T> PipeBorrow for T
pub fn pipe_borrow<'a, T, R>(&'a self, func: impl FnOnce(&'a T) -> R) -> R where
Self: Borrow<T>,
T: 'a,
R: 'a,
Self: Borrow<T>,
T: 'a,
R: 'a,
pub fn pipe_borrow_mut<'a, T, R>(
&'a mut self,
func: impl FnOnce(&'a mut T) -> R
) -> R where
Self: BorrowMut<T>,
T: 'a,
R: 'a,
&'a mut self,
func: impl FnOnce(&'a mut T) -> R
) -> R where
Self: BorrowMut<T>,
T: 'a,
R: 'a,
impl<T> PipeDeref for T
pub fn pipe_deref<'a, R>(
&'a self,
func: impl FnOnce(&'a Self::Target) -> R
) -> R where
Self: Deref,
R: 'a,
&'a self,
func: impl FnOnce(&'a Self::Target) -> R
) -> R where
Self: Deref,
R: 'a,
pub fn pipe_deref_mut<'a, R>(
&'a mut self,
func: impl FnOnce(&'a mut Self::Target) -> R
) -> R where
Self: DerefMut,
R: 'a,
&'a mut self,
func: impl FnOnce(&'a mut Self::Target) -> R
) -> R where
Self: DerefMut,
R: 'a,
impl<T> PipeRef for T
pub fn pipe_ref<'a, R>(&'a self, func: impl FnOnce(&'a Self) -> R) -> R where
R: 'a,
R: 'a,
pub fn pipe_mut<'a, R>(&'a mut self, func: impl FnOnce(&'a mut Self) -> R) -> R where
R: 'a,
R: 'a,
impl<T> Tap for T
pub fn tap(self, func: impl FnOnce(&Self)) -> Self
pub fn tap_mut(self, func: impl FnOnce(&mut Self)) -> Self
pub fn tap_borrow<B>(self, func: impl FnOnce(&B)) -> Self where
Self: Borrow<B>,
B: ?Sized,
Self: Borrow<B>,
B: ?Sized,
pub fn tap_borrow_mut<B>(self, func: impl FnOnce(&mut B)) -> Self where
Self: BorrowMut<B>,
B: ?Sized,
Self: BorrowMut<B>,
B: ?Sized,
pub fn tap_ref<R>(self, func: impl FnOnce(&R)) -> Self where
Self: AsRef<R>,
R: ?Sized,
Self: AsRef<R>,
R: ?Sized,
pub fn tap_ref_mut<R>(self, func: impl FnOnce(&mut R)) -> Self where
Self: AsMut<R>,
R: ?Sized,
Self: AsMut<R>,
R: ?Sized,
pub fn tap_deref<T>(self, func: impl FnOnce(&T)) -> Self where
Self: Deref<Target = T>,
T: ?Sized,
Self: Deref<Target = T>,
T: ?Sized,
pub fn tap_deref_mut<T>(self, func: impl FnOnce(&mut T)) -> Self where
Self: DerefMut<Target = T> + Deref,
T: ?Sized,
Self: DerefMut<Target = T> + Deref,
T: ?Sized,
pub fn tap_dbg(self, func: impl FnOnce(&Self)) -> Self
pub fn tap_mut_dbg(self, func: impl FnOnce(&mut Self)) -> Self
pub fn tap_borrow_dbg<B>(self, func: impl FnOnce(&B)) -> Self where
Self: Borrow<B>,
B: ?Sized,
Self: Borrow<B>,
B: ?Sized,
pub fn tap_borrow_mut_dbg<B>(self, func: impl FnOnce(&mut B)) -> Self where
Self: BorrowMut<B>,
B: ?Sized,
Self: BorrowMut<B>,
B: ?Sized,
pub fn tap_ref_dbg<R>(self, func: impl FnOnce(&R)) -> Self where
Self: AsRef<R>,
R: ?Sized,
Self: AsRef<R>,
R: ?Sized,
pub fn tap_ref_mut_dbg<R>(self, func: impl FnOnce(&mut R)) -> Self where
Self: AsMut<R>,
R: ?Sized,
Self: AsMut<R>,
R: ?Sized,
pub fn tap_deref_dbg<T>(self, func: impl FnOnce(&T)) -> Self where
Self: Deref<Target = T>,
T: ?Sized,
Self: Deref<Target = T>,
T: ?Sized,
pub fn tap_deref_mut_dbg<T>(self, func: impl FnOnce(&mut T)) -> Self where
Self: DerefMut<Target = T> + Deref,
T: ?Sized,
Self: DerefMut<Target = T> + Deref,
T: ?Sized,
impl<T> Tap for T
pub fn tap<F, R>(self, func: F) -> Self where
F: FnOnce(&Self) -> R,
F: FnOnce(&Self) -> R,
pub fn tap_dbg<F, R>(self, func: F) -> Self where
F: FnOnce(&Self) -> R,
F: FnOnce(&Self) -> R,
pub fn tap_mut<F, R>(self, func: F) -> Self where
F: FnOnce(&mut Self) -> R,
F: FnOnce(&mut Self) -> R,
pub fn tap_mut_dbg<F, R>(self, func: F) -> Self where
F: FnOnce(&mut Self) -> R,
F: FnOnce(&mut Self) -> R,
impl<T, U> TapAsRef<U> for T where
U: ?Sized,
U: ?Sized,
pub fn tap_ref<F, R>(self, func: F) -> Self where
Self: AsRef<T>,
F: FnOnce(&T) -> R,
Self: AsRef<T>,
F: FnOnce(&T) -> R,
pub fn tap_ref_dbg<F, R>(self, func: F) -> Self where
Self: AsRef<T>,
F: FnOnce(&T) -> R,
Self: AsRef<T>,
F: FnOnce(&T) -> R,
pub fn tap_ref_mut<F, R>(self, func: F) -> Self where
Self: AsMut<T>,
F: FnOnce(&mut T) -> R,
Self: AsMut<T>,
F: FnOnce(&mut T) -> R,
pub fn tap_ref_mut_dbg<F, R>(self, func: F) -> Self where
Self: AsMut<T>,
F: FnOnce(&mut T) -> R,
Self: AsMut<T>,
F: FnOnce(&mut T) -> R,
impl<T, U> TapBorrow<U> for T where
U: ?Sized,
U: ?Sized,
pub fn tap_borrow<F, R>(self, func: F) -> Self where
Self: Borrow<T>,
F: FnOnce(&T) -> R,
Self: Borrow<T>,
F: FnOnce(&T) -> R,
pub fn tap_borrow_dbg<F, R>(self, func: F) -> Self where
Self: Borrow<T>,
F: FnOnce(&T) -> R,
Self: Borrow<T>,
F: FnOnce(&T) -> R,
pub fn tap_borrow_mut<F, R>(self, func: F) -> Self where
Self: BorrowMut<T>,
F: FnOnce(&mut T) -> R,
Self: BorrowMut<T>,
F: FnOnce(&mut T) -> R,
pub fn tap_borrow_mut_dbg<F, R>(self, func: F) -> Self where
Self: BorrowMut<T>,
F: FnOnce(&mut T) -> R,
Self: BorrowMut<T>,
F: FnOnce(&mut T) -> R,
impl<T> TapDeref for T
pub fn tap_deref<F, R>(self, func: F) -> Self where
Self: Deref,
F: FnOnce(&Self::Target) -> R,
Self: Deref,
F: FnOnce(&Self::Target) -> R,
pub fn tap_deref_dbg<F, R>(self, func: F) -> Self where
Self: Deref,
F: FnOnce(&Self::Target) -> R,
Self: Deref,
F: FnOnce(&Self::Target) -> R,
pub fn tap_deref_mut<F, R>(self, func: F) -> Self where
Self: DerefMut,
F: FnOnce(&mut Self::Target) -> R,
Self: DerefMut,
F: FnOnce(&mut Self::Target) -> R,
pub fn tap_deref_mut_dbg<F, R>(self, func: F) -> Self where
Self: DerefMut,
F: FnOnce(&mut Self::Target) -> R,
Self: DerefMut,
F: FnOnce(&mut Self::Target) -> R,
impl<T> ToOwned for T where
T: Clone,
[src]
T: Clone,
type Owned = T
The resulting type after obtaining ownership.
pub fn to_owned(&self) -> T
[src]
pub fn clone_into(&self, target: &mut T)
[src]
impl<T> TryConv for T
impl<T> TryConv for T
impl<T, U> TryFrom<U> for T where
U: Into<T>,
[src]
U: Into<T>,
type Error = Infallible
The type returned in the event of a conversion error.
pub fn try_from(value: U) -> Result<T, <T as TryFrom<U>>::Error>
[src]
impl<T, U> TryInto<U> for T where
U: TryFrom<T>,
[src]
U: TryFrom<T>,