std::option::Option - Rust
Description: API documentation for the Rust `Option` enum in crate `std`.
Keywords: rust, rustlang, rust-lang, Option

# 1.0.0[−][src]Enum std::option::Option

    pub enum Option<T> {
        None,
        Some(T),
    }

The `Option` type. See the module level documentation for more.

## Variants

`None`

No value

`Some(T)`

Some value `T`

## Methods

### `impl<T> Option<T>`[src]

#### `pub fn is_some(&self) -> bool`[src]

Returns `true` if the option is a `Some` value.

# Examples

    let x: Option<u32> = Some(2);
    assert_eq!(x.is_some(), true);

    let x: Option<u32> = None;
    assert_eq!(x.is_some(), false);Run

#### `pub fn is_none(&self) -> bool`[src]

Returns `true` if the option is a `None` value.

# Examples

    let x: Option<u32> = Some(2);
    assert_eq!(x.is_none(), false);

    let x: Option<u32> = None;
    assert_eq!(x.is_none(), true);Run

#### `pub fn as_ref(&self) -> Option<&T>`[src]

Converts from `Option<T>` to `Option<&T>`.

# Examples

Convert an `Option<``String``>` into an `Option<``usize``>`, preserving the original. The `map` method takes the `self` argument by value, consuming the original, so this technique uses `as_ref` to first take an `Option` to a reference to the value inside the original.

    let text: Option<String> = Some("Hello, world!".to_string());
    // First, cast `Option<String>` to `Option<&String>` with `as_ref`,
    // then consume *that* with `map`, leaving `text` on the stack.
    let text_length: Option<usize> = text.as_ref().map(|s| s.len());
    println!("still can print text: {:?}", text);Run

#### `pub fn as_mut(&mut self) -> Option<&mut T>`[src]

Converts from `Option<T>` to `Option<&mut T>`.

# Examples

    let mut x = Some(2);
    match x.as_mut() {
        Some(v) => *v = 42,
        None => {},
    }
    assert_eq!(x, Some(42));Run

#### `pub fn as_pin_ref(self: Pin<&'a Option<T>>) -> Option<Pin<&'a T>>`
1.33.0
[src]

Converts from `Pin<&Option<T>>` to `Option<Pin<&T>>`

#### `pub fn as_pin_mut(self: Pin<&'a mut Option<T>>) -> Option<Pin<&'a mut T>>`
1.33.0
[src]

Converts from `Pin<&mut Option<T>>` to `Option<Pin<&mut T>>`

#### `pub fn expect(self, msg: &str) -> T`[src]

Unwraps an option, yielding the content of a `Some`.

# Panics

Panics if the value is a `None` with a custom panic message provided by `msg`.

# Examples

    let x = Some("value");
    assert_eq!(x.expect("the world is ending"), "value");Run

    let x: Option<&str> = None;
    x.expect("the world is ending"); // panics with `the world is ending`Run

#### `pub fn unwrap(self) -> T`[src]

Moves the value `v` out of the `Option<T>` if it is `Some(v)`.

In general, because this function may panic, its use is discouraged. Instead, prefer to use pattern matching and handle the `None` case explicitly.

# Panics

Panics if the self value equals `None`.

# Examples

    let x = Some("air");
    assert_eq!(x.unwrap(), "air");Run

    let x: Option<&str> = None;
    assert_eq!(x.unwrap(), "air"); // failsRun

#### `pub fn unwrap_or(self, def: T) -> T`[src]

Returns the contained value or a default.

Arguments passed to `unwrap_or` are eagerly evaluated; if you are passing the result of a function call, it is recommended to use `unwrap_or_else`, which is lazily evaluated.

# Examples

    assert_eq!(Some("car").unwrap_or("bike"), "car");
    assert_eq!(None.unwrap_or("bike"), "bike");Run

#### `pub fn unwrap_or_else<F>(self, f: F) -> T where
F: FnOnce() -> T,` [src]

Returns the contained value or computes it from a closure.

# Examples

    let k = 10;
    assert_eq!(Some(4).unwrap_or_else(|| 2 * k), 4);
    assert_eq!(None.unwrap_or_else(|| 2 * k), 20);Run

#### `pub fn map<U, F>(self, f: F) -> Option<U> where
F: FnOnce(T) -> U,` [src]

Maps an `Option<T>` to `Option<U>` by applying a function to a contained value.

# Examples

Convert an `Option<``String``>` into an `Option<``usize``>`, consuming the original:

    let maybe_some_string = Some(String::from("Hello, World!"));
    // `Option::map` takes self *by value*, consuming `maybe_some_string`
    let maybe_some_len = maybe_some_string.map(|s| s.len());

    assert_eq!(maybe_some_len, Some(13));Run

#### `pub fn map_or<U, F>(self, default: U, f: F) -> U where
F: FnOnce(T) -> U,` [src]

Applies a function to the contained value (if any), or returns the provided default (if not).

# Examples

    let x = Some("foo");
    assert_eq!(x.map_or(42, |v| v.len()), 3);

    let x: Option<&str> = None;
    assert_eq!(x.map_or(42, |v| v.len()), 42);Run

#### `pub fn map_or_else<U, D, F>(self, default: D, f: F) -> U where
D: FnOnce() -> U,
F: FnOnce(T) -> U,` [src]

Applies a function to the contained value (if any), or computes a default (if not).

# Examples

    let k = 21;

    let x = Some("foo");
    assert_eq!(x.map_or_else(|| 2 * k, |v| v.len()), 3);

    let x: Option<&str> = None;
    assert_eq!(x.map_or_else(|| 2 * k, |v| v.len()), 42);Run

#### `pub fn ok_or<E>(self, err: E) -> Result<T, E>`[src]

Transforms the `Option<T>` into a `Result<T, E>`, mapping `Some(v)` to `Ok(v)` and `None` to `Err(err)`.

Arguments passed to `ok_or` are eagerly evaluated; if you are passing the result of a function call, it is recommended to use `ok_or_else`, which is lazily evaluated.

# Examples

    let x = Some("foo");
    assert_eq!(x.ok_or(0), Ok("foo"));

    let x: Option<&str> = None;
    assert_eq!(x.ok_or(0), Err(0));Run

#### `pub fn ok_or_else<E, F>(self, err: F) -> Result<T, E> where
F: FnOnce() -> E,` [src]

Transforms the `Option<T>` into a `Result<T, E>`, mapping `Some(v)` to `Ok(v)` and `None` to `Err(err())`.

# Examples

    let x = Some("foo");
    assert_eq!(x.ok_or_else(|| 0), Ok("foo"));

    let x: Option<&str> = None;
    assert_eq!(x.ok_or_else(|| 0), Err(0));Run

####
ⓘImportant traits for Iter<'a, A>

### Important traits for Iter<'a, A>

`impl<'a, A> Iterator for Iter<'a, A> type Item = &'a A;`
`pub fn iter(&self) -> Iter<T>`[src]

Returns an iterator over the possibly contained value.

# Examples

    let x = Some(4);
    assert_eq!(x.iter().next(), Some(&4));

    let x: Option<u32> = None;
    assert_eq!(x.iter().next(), None);Run

####
ⓘImportant traits for IterMut<'a, A>

### Important traits for IterMut<'a, A>

`impl<'a, A> Iterator for IterMut<'a, A> type Item = &'a mut A;`
`pub fn iter_mut(&mut self) -> IterMut<T>`[src]

Returns a mutable iterator over the possibly contained value.

# Examples

    let mut x = Some(4);
    match x.iter_mut().next() {
        Some(v) => *v = 42,
        None => {},
    }
    assert_eq!(x, Some(42));

    let mut x: Option<u32> = None;
    assert_eq!(x.iter_mut().next(), None);Run

#### `pub fn and<U>(self, optb: Option<U>) -> Option<U>`[src]

Returns `None` if the option is `None`, otherwise returns `optb`.

# Examples

    let x = Some(2);
    let y: Option<&str> = None;
    assert_eq!(x.and(y), None);

    let x: Option<u32> = None;
    let y = Some("foo");
    assert_eq!(x.and(y), None);

    let x = Some(2);
    let y = Some("foo");
    assert_eq!(x.and(y), Some("foo"));

    let x: Option<u32> = None;
    let y: Option<&str> = None;
    assert_eq!(x.and(y), None);Run

#### `pub fn and_then<U, F>(self, f: F) -> Option<U> where
F: FnOnce(T) -> Option<U>,` [src]

Returns `None` if the option is `None`, otherwise calls `f` with the wrapped value and returns the result.

Some languages call this operation flatmap.

# Examples

    fn sq(x: u32) -> Option<u32> { Some(x * x) }
    fn nope(_: u32) -> Option<u32> { None }

    assert_eq!(Some(2).and_then(sq).and_then(sq), Some(16));
    assert_eq!(Some(2).and_then(sq).and_then(nope), None);
    assert_eq!(Some(2).and_then(nope).and_then(sq), None);
    assert_eq!(None.and_then(sq).and_then(sq), None);Run

#### `pub fn filter<P>(self, predicate: P) -> Option<T> where
P: FnOnce(&T) -> bool,`
1.27.0
[src]

Returns `None` if the option is `None`, otherwise calls `predicate` with the wrapped value and returns:

- `Some(t)` if `predicate` returns `true` (where `t` is the wrapped value), and
- `None` if `predicate` returns `false`.

This function works similar to `Iterator::filter()`. You can imagine the `Option<T>` being an iterator over one or zero elements. `filter()` lets you decide which elements to keep.

# Examples

    fn is_even(n: &i32) -> bool {
        n % 2 == 0
    }

    assert_eq!(None.filter(is_even), None);
    assert_eq!(Some(3).filter(is_even), None);
    assert_eq!(Some(4).filter(is_even), Some(4));Run

#### `pub fn or(self, optb: Option<T>) -> Option<T>`[src]

Returns the option if it contains a value, otherwise returns `optb`.

Arguments passed to `or` are eagerly evaluated; if you are passing the result of a function call, it is recommended to use `or_else`, which is lazily evaluated.

# Examples

    let x = Some(2);
    let y = None;
    assert_eq!(x.or(y), Some(2));

    let x = None;
    let y = Some(100);
    assert_eq!(x.or(y), Some(100));

    let x = Some(2);
    let y = Some(100);
    assert_eq!(x.or(y), Some(2));

    let x: Option<u32> = None;
    let y = None;
    assert_eq!(x.or(y), None);Run

#### `pub fn or_else<F>(self, f: F) -> Option<T> where
F: FnOnce() -> Option<T>,` [src]

Returns the option if it contains a value, otherwise calls `f` and returns the result.

# Examples

    fn nobody() -> Option<&'static str> { None }
    fn vikings() -> Option<&'static str> { Some("vikings") }

    assert_eq!(Some("barbarians").or_else(vikings), Some("barbarians"));
    assert_eq!(None.or_else(vikings), Some("vikings"));
    assert_eq!(None.or_else(nobody), None);Run

#### `pub fn xor(self, optb: Option<T>) -> Option<T>`[src]

🔬 This is a nightly-only experimental API. (`option_xor` #50512)

Returns `Some` if exactly one of `self`, `optb` is `Some`, otherwise returns `None`.

# Examples

    #![feature(option_xor)]

    let x = Some(2);
    let y: Option<u32> = None;
    assert_eq!(x.xor(y), Some(2));

    let x: Option<u32> = None;
    let y = Some(2);
    assert_eq!(x.xor(y), Some(2));

    let x = Some(2);
    let y = Some(2);
    assert_eq!(x.xor(y), None);

    let x: Option<u32> = None;
    let y: Option<u32> = None;
    assert_eq!(x.xor(y), None);Run

####
ⓘImportant traits for &'_ mut I

### Important traits for &'_ mut I

`impl<'_, I> Iterator for &'_ mut I where
I: Iterator + ?Sized, type Item = <I as Iterator>::Item;impl<'a, R: Read + ?Sized> Read for &'a mut Rimpl<'a, W: Write + ?Sized> Write for &'a mut W`
`pub fn get_or_insert(&mut self, v: T) -> &mut T`
1.20.0
[src]

Inserts `v` into the option if it is `None`, then returns a mutable reference to the contained value.

# Examples

    let mut x = None;

    {
        let y: &mut u32 = x.get_or_insert(5);
        assert_eq!(y, &5);

        *y = 7;
    }

    assert_eq!(x, Some(7));Run

####
ⓘImportant traits for &'_ mut I

### Important traits for &'_ mut I

`impl<'_, I> Iterator for &'_ mut I where
I: Iterator + ?Sized, type Item = <I as Iterator>::Item;impl<'a, R: Read + ?Sized> Read for &'a mut Rimpl<'a, W: Write + ?Sized> Write for &'a mut W`
`pub fn get_or_insert_with<F>(&mut self, f: F) -> &mut T where
F: FnOnce() -> T,`
1.20.0
[src]

Inserts a value computed from `f` into the option if it is `None`, then returns a mutable reference to the contained value.

# Examples

    let mut x = None;

    {
        let y: &mut u32 = x.get_or_insert_with(|| 5);
        assert_eq!(y, &5);

        *y = 7;
    }

    assert_eq!(x, Some(7));Run

#### `pub fn take(&mut self) -> Option<T>`[src]

Takes the value out of the option, leaving a `None` in its place.

# Examples

    let mut x = Some(2);
    let y = x.take();
    assert_eq!(x, None);
    assert_eq!(y, Some(2));

    let mut x: Option<u32> = None;
    let y = x.take();
    assert_eq!(x, None);
    assert_eq!(y, None);Run

#### `pub fn replace(&mut self, value: T) -> Option<T>`
1.31.0
[src]

Replaces the actual value in the option by the value given in parameter, returning the old value if present, leaving a `Some` in its place without deinitializing either one.

# Examples

    let mut x = Some(2);
    let old = x.replace(5);
    assert_eq!(x, Some(5));
    assert_eq!(old, Some(2));

    let mut x = None;
    let old = x.replace(3);
    assert_eq!(x, Some(3));
    assert_eq!(old, None);Run

### `impl<'a, T> Option<&'a T> where
T: Copy,` [src]

#### `pub fn copied(self) -> Option<T>`[src]

🔬 This is a nightly-only experimental API. (`copied` #57126)

Maps an `Option<&T>` to an `Option<T>` by copying the contents of the option.

# Examples

    #![feature(copied)]

    let x = 12;
    let opt_x = Some(&x);
    assert_eq!(opt_x, Some(&12));
    let copied = opt_x.copied();
    assert_eq!(copied, Some(12));Run

### `impl<'a, T> Option<&'a mut T> where
T: Copy,` [src]

#### `pub fn copied(self) -> Option<T>`[src]

🔬 This is a nightly-only experimental API. (`copied` #57126)

Maps an `Option<&mut T>` to an `Option<T>` by copying the contents of the option.

# Examples

    #![feature(copied)]

    let mut x = 12;
    let opt_x = Some(&mut x);
    assert_eq!(opt_x, Some(&mut 12));
    let copied = opt_x.copied();
    assert_eq!(copied, Some(12));Run

### `impl<'a, T> Option<&'a T> where
T: Clone,` [src]

#### `pub fn cloned(self) -> Option<T>`[src]

Maps an `Option<&T>` to an `Option<T>` by cloning the contents of the option.

# Examples

    let x = 12;
    let opt_x = Some(&x);
    assert_eq!(opt_x, Some(&12));
    let cloned = opt_x.cloned();
    assert_eq!(cloned, Some(12));Run

### `impl<'a, T> Option<&'a mut T> where
T: Clone,` [src]

#### `pub fn cloned(self) -> Option<T>`
1.26.0
[src]

Maps an `Option<&mut T>` to an `Option<T>` by cloning the contents of the option.

# Examples

    let mut x = 12;
    let opt_x = Some(&mut x);
    assert_eq!(opt_x, Some(&mut 12));
    let cloned = opt_x.cloned();
    assert_eq!(cloned, Some(12));Run

### `impl<T> Option<T> where
T: Default,` [src]

#### `pub fn unwrap_or_default(self) -> T`[src]

Returns the contained value or a default

Consumes the `self` argument then, if `Some`, returns the contained value, otherwise if `None`, returns the default value for that type.

# Examples

Convert a string to an integer, turning poorly-formed strings into 0 (the default value for integers). `parse` converts a string to any other type that implements `FromStr`, returning `None` on error.

    let good_year_from_input = "1909";
    let bad_year_from_input = "190blarg";
    let good_year = good_year_from_input.parse().ok().unwrap_or_default();
    let bad_year = bad_year_from_input.parse().ok().unwrap_or_default();

    assert_eq!(1909, good_year);
    assert_eq!(0, bad_year);Run

### `impl<T> Option<T> where
T: Deref,` [src]

#### `pub fn deref(&self) -> Option<&<T as Deref>::Target>`[src]

🔬 This is a nightly-only experimental API. (`inner_deref` #50264)

newly added

Converts from `&Option<T>` to `Option<&T::Target>`.

Leaves the original Option in-place, creating a new one with a reference to the original one, additionally coercing the contents via `Deref`.

### `impl<T, E> Option<Result<T, E>>`[src]

#### `pub fn transpose(self) -> Result<Option<T>, E>`
1.33.0
[src]

Transposes an `Option` of a `Result` into a `Result` of an `Option`.

`None` will be mapped to `Ok(None)`. `Some(Ok(_))` and `Some(Err(_))` will be mapped to `Ok(Some(_))` and `Err(_)`.

# Examples

    #[derive(Debug, Eq, PartialEq)]
    struct SomeErr;

    let x: Result<Option<i32>, SomeErr> = Ok(Some(5));
    let y: Option<Result<i32, SomeErr>> = Some(Ok(5));
    assert_eq!(x, y.transpose());Run

## Trait Implementations

### `impl<A, V> FromIterator<Option<A>> for Option<V> where
V: FromIterator<A>,` [src]

#### `fn from_iter<I>(iter: I) -> Option<V> where
I: IntoIterator<Item = Option<A>>,` [src]

Takes each element in the `Iterator`: if it is `None`, no further elements are taken, and the `None` is returned. Should no `None` occur, a container with the values of each `Option` is returned.

# Examples

Here is an example which increments every integer in a vector. `We use the checked variant of`add`that returns`None` when the calculation would result in an overflow.

    let items = vec![0_u16, 1, 2];

    let res: Option<Vec<u16>> = items
        .iter()
        .map(|x| x.checked_add(1))
        .collect();

    assert_eq!(res, Some(vec![1, 2, 3]));Run

As you can see, this will return the expected, valid items.

Here is another example that tries to subtract one from another list of integers, this time checking for underflow:

    let items = vec![2_u16, 1, 0];

    let res: Option<Vec<u16>> = items
        .iter()
        .map(|x| x.checked_sub(1))
        .collect();

    assert_eq!(res, None);Run

Since the last element is zero, it would underflow. Thus, the resulting value is `None`.

### `impl<T> Default for Option<T>`[src]

#### `fn default() -> Option<T>`[src]

Returns `None`.

### `impl<T> Debug for Option<T> where
T: Debug,` [src]

#### `fn fmt(&self, f: &mut Formatter) -> Result<(), Error>`[src]

Formats the value using the given formatter. Read more

### `impl<T> Hash for Option<T> where
T: Hash,` [src]

#### `fn hash<__HT>(&self, state: &mut __HT) where
__HT: Hasher,` [src]

Feeds this value into the given [`Hasher`]. Read more

#### `fn hash_slice<H>(data: &[Self], state: &mut H) where
H: Hasher,`
1.3.0
[src]

Feeds a slice of this type into the given [`Hasher`]. Read more

### `impl<T> Clone for Option<T> where
T: Clone,` [src]

#### `fn clone(&self) -> Option<T>`[src]

Returns a copy of the value. Read more

#### `fn clone_from(&mut self, source: &Self)`[src]

Performs copy-assignment from `source`. Read more

### `impl<T> PartialOrd<Option<T>> for Option<T> where
T: PartialOrd<T>,` [src]

#### `fn partial_cmp(&self, other: &Option<T>) -> Option<Ordering>`[src]

This method returns an ordering between `self` and `other` values if one exists. Read more

#### `fn lt(&self, other: &Option<T>) -> bool`[src]

This method tests less than (for `self` and `other`) and is used by the `<` operator. Read more

#### `fn le(&self, other: &Option<T>) -> bool`[src]

This method tests less than or equal to (for `self` and `other`) and is used by the `<=` operator. Read more

#### `fn gt(&self, other: &Option<T>) -> bool`[src]

This method tests greater than (for `self` and `other`) and is used by the `>` operator. Read more

#### `fn ge(&self, other: &Option<T>) -> bool`[src]

This method tests greater than or equal to (for `self` and `other`) and is used by the `>=` operator. Read more

### `impl<T> Ord for Option<T> where
T: Ord,` [src]

#### `fn cmp(&self, other: &Option<T>) -> Ordering`[src]

This method returns an `Ordering` between `self` and `other`. Read more

#### `fn max(self, other: Self) -> Self`
1.21.0
[src]

Compares and returns the maximum of two values. Read more

#### `fn min(self, other: Self) -> Self`
1.21.0
[src]

Compares and returns the minimum of two values. Read more

### `impl<'a, T> IntoIterator for &'a Option<T>`
1.4.0
[src]

#### `type Item = &'a T`

The type of the elements being iterated over.

#### `type IntoIter = Iter<'a, T>`

Which kind of iterator are we turning this into?

####
ⓘImportant traits for Iter<'a, A>

### Important traits for Iter<'a, A>

`impl<'a, A> Iterator for Iter<'a, A> type Item = &'a A;`
`fn into_iter(self) -> Iter<'a, T>`[src]

Creates an iterator from a value. Read more

### `impl<'a, T> IntoIterator for &'a mut Option<T>`
1.4.0
[src]

#### `type Item = &'a mut T`

The type of the elements being iterated over.

#### `type IntoIter = IterMut<'a, T>`

Which kind of iterator are we turning this into?

####
ⓘImportant traits for IterMut<'a, A>

### Important traits for IterMut<'a, A>

`impl<'a, A> Iterator for IterMut<'a, A> type Item = &'a mut A;`
`fn into_iter(self) -> IterMut<'a, T>`[src]

Creates an iterator from a value. Read more

### `impl<T> IntoIterator for Option<T>`[src]

#### `type Item = T`

The type of the elements being iterated over.

#### `type IntoIter = IntoIter<T>`

Which kind of iterator are we turning this into?

####
ⓘImportant traits for IntoIter<A>

### Important traits for IntoIter<A>

`impl<A> Iterator for IntoIter<A> type Item = A;`
`fn into_iter(self) -> IntoIter<T>`[src]

Returns a consuming iterator over the possibly contained value.

# Examples

    let x = Some("string");
    let v: Vec<&str> = x.into_iter().collect();
    assert_eq!(v, ["string"]);

    let x = None;
    let v: Vec<&str> = x.into_iter().collect();
    assert!(v.is_empty());Run

### `impl<T> Eq for Option<T> where
T: Eq,` [src]

### `impl<T> PartialEq<Option<T>> for Option<T> where
T: PartialEq<T>,` [src]

#### `fn eq(&self, other: &Option<T>) -> bool`[src]

This method tests for `self` and `other` values to be equal, and is used by `==`. Read more

#### `fn ne(&self, other: &Option<T>) -> bool`[src]

This method tests for `!=`.

### `impl<'a, T> From<&'a Option<T>> for Option<&'a T>`
1.30.0
[src]

#### `fn from(o: &'a Option<T>) -> Option<&'a T>`[src]

Performs the conversion.

### `impl<T> From<T> for Option<T>`
1.12.0
[src]

#### `fn from(val: T) -> Option<T>`[src]

Performs the conversion.

### `impl<'a, T> From<&'a mut Option<T>> for Option<&'a mut T>`
1.30.0
[src]

#### `fn from(o: &'a mut Option<T>) -> Option<&'a mut T>`[src]

Performs the conversion.

### `impl<T> Try for Option<T>`[src]

#### `type Ok = T`

🔬 This is a nightly-only experimental API. (`try_trait` #42327)

The type of this value when viewed as successful.

#### `type Error = NoneError`

🔬 This is a nightly-only experimental API. (`try_trait` #42327)

The type of this value when viewed as failed.

#### `fn into_result(self) -> Result<T, NoneError>`[src]

🔬 This is a nightly-only experimental API. (`try_trait` #42327)

Applies the "?" operator. A return of `Ok(t)` means that the execution should continue normally, and the result of `?` is the value `t`. A return of `Err(e)` means that execution should branch to the innermost enclosing `catch`, or return from the function. Read more

#### `fn from_ok(v: T) -> Option<T>`[src]

🔬 This is a nightly-only experimental API. (`try_trait` #42327)

Wrap an OK value to construct the composite result. For example, `Result::Ok(x)` and `Result::from_ok(x)` are equivalent. Read more

#### `fn from_error(NoneError) -> Option<T>`[src]

🔬 This is a nightly-only experimental API. (`try_trait` #42327)

Wrap an error value to construct the composite result. For example, `Result::Err(x)` and `Result::from_error(x)` are equivalent. Read more

### `impl<T> Copy for Option<T> where
T: Copy,` [src]

## Auto Trait Implementations

### `impl<T> Send for Option<T> where
T: Send,`

### `impl<T> Sync for Option<T> where
T: Sync,`

## Blanket Implementations

### `impl<T> From for T`[src]

#### `fn from(t: T) -> T`[src]

Performs the conversion.

### `impl<I> IntoIterator for I where
I: Iterator,` [src]

#### `type Item = <I as Iterator>::Item`

The type of the elements being iterated over.

#### `type IntoIter = I`

Which kind of iterator are we turning this into?

#### `fn into_iter(self) -> I`[src]

Creates an iterator from a value. Read more

### `impl<T, U> TryFrom for T where
T: From<U>,` [src]

#### `type Error = !`

🔬 This is a nightly-only experimental API. (`try_from` #33417)

The type returned in the event of a conversion error.

#### `fn try_from(value: U) -> Result<T, <T as TryFrom<U>>::Error>`[src]

🔬 This is a nightly-only experimental API. (`try_from` #33417)

Performs the conversion.

### `impl<T, U> TryInto for T where
U: TryFrom<T>,` [src]

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

🔬 This is a nightly-only experimental API. (`try_from` #33417)

The type returned in the event of a conversion error.

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

🔬 This is a nightly-only experimental API. (`try_from` #33417)

Performs the conversion.

### `impl<T, U> Into for T where
U: From<T>,` [src]

#### `fn into(self) -> U`[src]

Performs the conversion.

### `impl<T> Borrow for T where
T: ?Sized,` [src]

####
ⓘImportant traits for &'_ mut I

### Important traits for &'_ mut I

`impl<'_, I> Iterator for &'_ mut I where
I: Iterator + ?Sized, type Item = <I as Iterator>::Item;impl<'a, R: Read + ?Sized> Read for &'a mut Rimpl<'a, W: Write + ?Sized> Write for &'a mut W`
`fn borrow(&self) -> &T`[src]

Immutably borrows from an owned value. Read more

### `impl<T> BorrowMut for T where
T: ?Sized,` [src]

####
ⓘImportant traits for &'_ mut I

### Important traits for &'_ mut I

`impl<'_, I> Iterator for &'_ mut I where
I: Iterator + ?Sized, type Item = <I as Iterator>::Item;impl<'a, R: Read + ?Sized> Read for &'a mut Rimpl<'a, W: Write + ?Sized> Write for &'a mut W`
`fn borrow_mut(&mut self) -> &mut T`[src]

Mutably borrows from an owned value. Read more

### `impl<T> Any for T where
T: 'static + ?Sized,` [src]

#### `fn get_type_id(&self) -> TypeId`[src]

🔬 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,` [src]

#### `type Owned = T`

#### `fn to_owned(&self) -> T`[src]

Creates owned data from borrowed data, usually by cloning. Read more

#### `fn clone_into(&self, target: &mut T)`[src]

🔬 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

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