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

# 1.34.0[−][src]Enum std::convert::Infallible

    pub enum Infallible {}

The error type for errors that can never happen.

Since this enum has no variant, a value of this type can never actually exist. This can be useful for generic APIs that use `Result` and parameterize the error type, to indicate that the result is always `Ok`.

For example, the `TryFrom` trait (conversion that returns a `Result`) has a blanket implementation for all types where a reverse `Into` implementation exists.

ⓘThis example is not tested

    impl<T, U> TryFrom<U> for T where U: Into<T> {
        type Error = Infallible;

        fn try_from(value: U) -> Result<Self, Infallible> {
            Ok(U::into(value))  // Never returns `Err`
        }
    }Run

# Future compatibility

This enum has the same role as the `!` “never” type, which is unstable in this version of Rust. When `!` is stabilized, we plan to make `Infallible` a type alias to it:

ⓘThis example is not tested

    pub type Infallible = !;Run

… and eventually deprecate `Infallible`.

However there is one case where `!` syntax can be used before `!` is stabilized as a full-fleged type: in the position of a function’s return type. Specifically, it is possible implementations for two different function pointer types:

    trait MyTrait {}
    impl MyTrait for fn() -> ! {}
    impl MyTrait for fn() -> std::convert::Infallible {}Run

With `Infallible` being an enum, this code is valid. However when `Infallible` becomes an alias for the never type, the two `impl`s will start to overlap and therefore will be disallowed by the language’s trait coherence rules.

## Trait Implementations

### `impl Eq for Infallible`[src]

### `impl From<Infallible> for TryFromSliceError` 1.36.0[src]

#### `fn from(x: Infallible) -> TryFromSliceError`[src]

Performs the conversion.

### `impl From<Infallible> for TryFromIntError`[src]

#### `fn from(x: Infallible) -> TryFromIntError`[src]

Performs the conversion.

### `impl From<!> for Infallible`[src]

#### `fn from(x: !) -> Infallible`[src]

Performs the conversion.

### `impl PartialEq<Infallible> for Infallible`[src]

#### `fn eq(&self, &Infallible) -> bool`[src]

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

#### `#[must_use] fn ne(&self, other: &Rhs) -> bool`1.0.0[src]

This method tests for `!=`.

### `impl Ord for Infallible`[src]

#### `fn cmp(&self, _other: &Infallible) -> 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

#### `fn clamp(self, min: Self, max: Self) -> Self`[src]

🔬 This is a nightly-only experimental API. (`clamp` #44095)

Restrict a value to a certain interval. Read more

### `impl Display for Infallible`[src]

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

Formats the value using the given formatter. Read more

### `impl Debug for Infallible`[src]

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

Formats the value using the given formatter. Read more

### `impl Clone for Infallible`[src]

#### `fn clone(&self) -> Infallible`[src]

Returns a copy of the value. Read more

#### `fn clone_from(&mut self, source: &Self)`1.0.0[src]

Performs copy-assignment from `source`. Read more

### `impl PartialOrd<Infallible> for Infallible`[src]

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

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

#### `#[must_use] fn lt(&self, other: &Rhs) -> bool`1.0.0[src]

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

#### `#[must_use] fn le(&self, other: &Rhs) -> bool`1.0.0[src]

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

#### `#[must_use] fn gt(&self, other: &Rhs) -> bool`1.0.0[src]

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

#### `#[must_use] fn ge(&self, other: &Rhs) -> bool`1.0.0[src]

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

### `impl Copy for Infallible`[src]

## Auto Trait Implementations

### `impl UnwindSafe for Infallible`

### `impl RefUnwindSafe for Infallible`

### `impl Unpin for Infallible`

### `impl Send for Infallible`

### `impl Sync for Infallible`

## Blanket Implementations

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

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

Performs the conversion.

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

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

Performs the conversion.

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

#### `type Error = Infallible`

The type returned in the event of a conversion error.

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

Performs the conversion.

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

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

Performs the conversion.

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

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

The type returned in the event of a conversion error.

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

Performs the conversion.

### `impl<T> Borrow<T> 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<'_, F> Future for &'_ mut F where
F: Unpin + Future + ?Sized, type Output = <F as Future>::Output;impl<'_, R: Read + ?Sized> Read for &'_ mut Rimpl<'_, W: Write + ?Sized> Write for &'_ mut W`
`fn borrow(&self) -> &T`[src]

Immutably borrows from an owned value. Read more

### `impl<T> BorrowMut<T> 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<'_, F> Future for &'_ mut F where
F: Unpin + Future + ?Sized, type Output = <F as Future>::Output;impl<'_, R: Read + ?Sized> Read for &'_ mut Rimpl<'_, W: Write + ?Sized> Write for &'_ 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 type_id(&self) -> TypeId`[src]

Gets the `TypeId` of `self`. Read more

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

#### `type Owned = T`

The resulting type after obtaining ownership.

#### `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

### `impl<T> ToString for T where
T: Display + ?Sized,` [src]

#### `default fn to_string(&self) -> String`[src]

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