# Struct hashbrown::hash_map::OccupiedError

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    pub struct OccupiedError<'a, K, V, S, A: Allocator + Clone = Global> {
        pub entry: OccupiedEntry<'a, K, V, S, A>,
        pub value: V,
    }

Expand description

The error returned by `try_insert` when the key already exists.

Contains the occupied entry, and the value that was not inserted.

## Examples

    use hashbrown::hash_map::{HashMap, OccupiedError};

    let mut map: HashMap<_, _> = [("a", 10), ("b", 20)].into();

    // try_insert method returns mutable reference to the value if keys are vacant,
    // but if the map did have key present, nothing is updated, and the provided
    // value is returned inside `Err(_)` variant
    match map.try_insert("a", 100) {
        Err(OccupiedError { mut entry, value }) => {
            assert_eq!(entry.key(), &"a");
            assert_eq!(value, 100);
            assert_eq!(entry.insert(100), 10)
        }
        _ => unreachable!(),
    }
    assert_eq!(map[&"a"], 100);

## Fields

`entry: OccupiedEntry<'a, K, V, S, A>`

The entry in the map that was already occupied.

`value: V`

The value which was not inserted, because the entry was already occupied.

## Trait Implementations

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### impl<K: Debug, V: Debug, S, A: Allocator + Clone> Debug for OccupiedError<'_, K, V, S, A>

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

Formats the value using the given formatter. Read more

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### impl<'a, K: Debug, V: Debug, S, A: Allocator + Clone> Display for OccupiedError<'a, K, V, S, A>

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

Formats the value using the given formatter. Read more

## Auto Trait Implementations

### impl<'a, K, V, S, A> RefUnwindSafe for OccupiedError<'a, K, V, S, A> where
A: RefUnwindSafe,
K: RefUnwindSafe,
S: RefUnwindSafe,
V: RefUnwindSafe,

### impl<'a, K, V, S, A> Send for OccupiedError<'a, K, V, S, A> where
A: Send,
K: Send,
S: Send,
V: Send,

### impl<'a, K, V, S, A> Sync for OccupiedError<'a, K, V, S, A> where
A: Sync,
K: Sync,
S: Sync,
V: Sync,

### impl<'a, K, V, S, A> Unpin for OccupiedError<'a, K, V, S, A> where
K: Unpin,
V: Unpin,

### impl<'a, K, V, S, A = Global> !UnwindSafe for OccupiedError<'a, K, V, S, 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,

const: unstable · source

#### 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,

const: unstable · source

#### 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

const: unstable · source

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

Returns the argument unchanged.

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

const: unstable · source

#### 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> ToString for T where
T: Display + ?Sized,

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#### default fn to_string(&self) -> String

Converts the given value to a `String`. Read more

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

#### type Error = Infallible

The type returned in the event of a conversion error.

const: unstable · source

#### 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>,

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

The type returned in the event of a conversion error.

const: unstable · source

#### fn try_into(self) -> Result<U, <U as TryFrom<T>>::Error>

Performs the conversion.