VacantEntry in std::collections::btree_set - Rust
Description: A view into a vacant entry in a `BTreeSet`. It is part of the `Entry` enum.

## VacantEntry

# Struct VacantEntry

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    pub struct VacantEntry<'a, T, A = Global>where
        A: Allocator + Clone,{ /* private fields */ }

🔬This is a nightly-only experimental API. (`btree_set_entry` #133549)
Expand description

A view into a vacant entry in a `BTreeSet`. It is part of the `Entry` enum.

## §Examples

    #![feature(btree_set_entry)]

    use std::collections::btree_set::{Entry, BTreeSet};

    let mut set = BTreeSet::<&str>::new();

    let entry_v = match set.entry("a") {
        Entry::Vacant(view) => view,
        Entry::Occupied(_) => unreachable!(),
    };
    entry_v.insert();
    assert!(set.contains("a") && set.len() == 1);

    // Nonexistent key (insert)
    match set.entry("b") {
        Entry::Vacant(view) => view.insert(),
        Entry::Occupied(_) => unreachable!(),
    }
    assert!(set.contains("b") && set.len() == 2);

## Implementations§

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### impl<'a, T, A> VacantEntry<'a, T, A>
where T: Ord, A: Allocator + Clone,

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#### pub fn get(&self) -> &T

🔬This is a nightly-only experimental API. (`btree_set_entry` #133549)

Gets a reference to the value that would be used when inserting through the `VacantEntry`.

##### §Examples

    #![feature(btree_set_entry)]

    use std::collections::BTreeSet;

    let mut set = BTreeSet::new();
    assert_eq!(set.entry("poneyland").get(), &"poneyland");

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#### pub fn into_value(self) -> T

🔬This is a nightly-only experimental API. (`btree_set_entry` #133549)

Take ownership of the value.

##### §Examples

    #![feature(btree_set_entry)]

    use std::collections::btree_set::{Entry, BTreeSet};

    let mut set = BTreeSet::new();

    match set.entry("poneyland") {
        Entry::Occupied(_) => panic!(),
        Entry::Vacant(v) => assert_eq!(v.into_value(), "poneyland"),
    }

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#### pub fn insert(self)

🔬This is a nightly-only experimental API. (`btree_set_entry` #133549)

Sets the value of the entry with the VacantEntry’s value.

##### §Examples

    #![feature(btree_set_entry)]

    use std::collections::BTreeSet;
    use std::collections::btree_set::Entry;

    let mut set = BTreeSet::new();

    if let Entry::Vacant(o) = set.entry("poneyland") {
        o.insert();
    }
    assert!(set.contains("poneyland"));

## Trait Implementations§

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### impl<T, A> Debug for VacantEntry<'_, T, A>
where T: Debug + Ord, A: Allocator + Clone,

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#### fn fmt(&self, f: &mut Formatter<'_>) -> Result<(), Error>

Formats the value using the given formatter. Read more

## Auto Trait Implementations§

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### impl<'a, T, A> Freeze for VacantEntry<'a, T, A>
where T: Freeze, A: Freeze,

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### impl<'a, T, A> RefUnwindSafe for VacantEntry<'a, T, A>
where T: RefUnwindSafe, A: RefUnwindSafe,

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### impl<'a, T, A> Send for VacantEntry<'a, T, A>
where T: Send, A: Send,

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### impl<'a, T, A> Sync for VacantEntry<'a, T, A>
where T: Sync, A: Sync,

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### impl<'a, T, A> Unpin for VacantEntry<'a, T, A>
where T: Unpin, A: Unpin,

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### impl<'a, T, A = Global> !UnwindSafe for VacantEntry<'a, T, A>

## Blanket Implementations§

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### impl<T> Any for T
where T: 'static + ?Sized,

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#### fn type_id(&self) -> TypeId

Gets the `TypeId` of `self`. Read more
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### impl<T> Borrow<T> for T
where T: ?Sized,

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#### fn borrow(&self) -> &T

Immutably borrows from an owned value. Read more
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### impl<T> BorrowMut<T> for T
where T: ?Sized,

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#### fn borrow_mut(&mut self) -> &mut T

Mutably borrows from an owned value. Read more
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### impl<T> From<T> for T

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#### fn from(t: T) -> T

Returns the argument unchanged.

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### impl<T, U> Into<U> for T
where U: From<T>,

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#### fn into(self) -> U

Calls `U::from(self)`.

That is, this conversion is whatever the implementation of `From<T> for U` chooses to do.

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### impl<T, U> TryFrom<U> for T
where U: Into<T>,

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#### type Error = Infallible

The type returned in the event of a conversion error.
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#### fn try_from(value: U) -> Result<T, <T as TryFrom<U>>::Error>

Performs the conversion.
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### impl<T, U> TryInto<U> for T
where U: TryFrom<T>,

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#### type Error = <U as TryFrom<T>>::Error

The type returned in the event of a conversion error.
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#### fn try_into(self) -> Result<U, <U as TryFrom<T>>::Error>

Performs the conversion.