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.
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`
}
}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:
pub type Infallible = !;
… and eventually deprecate Infallible.
However there is one case where ! syntax can be used before ! is stabilized as a full-fledged 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 {}With Infallible being an enum, this code is valid. However when Infallible becomes an alias for the never type, the two impls will start to overlap and therefore will be disallowed by the language’s trait coherence rules.
impl Clone for Infallible[src]
fn clone(&self) -> Infallible[src]
fn clone_from(&mut self, source: &Self)[src]1.0.0
impl Copy for Infallible[src]
impl Debug for Infallible[src]
impl Display for Infallible[src]
impl Eq for Infallible[src]
impl Error for Infallible[src]1.8.0
fn description(&self) -> &str[src]
fn source(&self) -> Option<&(dyn Error + 'static)>[src]1.30.0
fn backtrace(&self) -> Option<&Backtrace>[src]
fn cause(&self) -> Option<&dyn Error>[src]1.0.0
impl From<!> for Infallible[src]
fn from(x: !) -> Infallible[src]
impl From<Infallible> for TryFromIntError[src]
fn from(x: Infallible) -> TryFromIntError[src]
impl From<Infallible> for TryFromSliceError[src]1.36.0
fn from(x: Infallible) -> TryFromSliceError[src]
impl Hash for Infallible[src]1.44.0
fn hash<H>(&self, &mut H) where
H: Hasher, [src]
fn hash_slice<H>(data: &[Self], state: &mut H) where
H: Hasher, [src]1.3.0
impl Ord for Infallible[src]
fn cmp(&self, _other: &Infallible) -> Ordering[src]
fn max(self, other: Self) -> Self[src]1.21.0
fn min(self, other: Self) -> Self[src]1.21.0
fn clamp(self, min: Self, max: Self) -> Self[src]
impl PartialEq<Infallible> for Infallible[src]
impl PartialOrd<Infallible> for Infallible[src]
impl RefUnwindSafe for Infallibleimpl Send for Infallibleimpl Sync for Infallibleimpl Unpin for Infallibleimpl UnwindSafe for Infallibleimpl<T> Any for T where
T: 'static + ?Sized, [src]
impl<T> Borrow<T> for T where
T: ?Sized, [src]
fn borrow(&self) -> &TⓘNotable traits for &'_ mut F
impl<'_, F> Future for &'_ mut F where
F: Unpin + Future + ?Sized,
type Output = <F as Future>::Output;
impl<'_, I> Iterator for &'_ mut I where
I: Iterator + ?Sized,
type Item = <I as Iterator>::Item;
impl<R: Read + ?Sized, '_> Read for &'_ mut R
impl<W: Write + ?Sized, '_> Write for &'_ mut W
[src]
impl<T> BorrowMut<T> for T where
T: ?Sized, [src]
fn borrow_mut(&mut self) -> &mut TⓘNotable traits for &'_ mut F
impl<'_, F> Future for &'_ mut F where
F: Unpin + Future + ?Sized,
type Output = <F as Future>::Output;
impl<'_, I> Iterator for &'_ mut I where
I: Iterator + ?Sized,
type Item = <I as Iterator>::Item;
impl<R: Read + ?Sized, '_> Read for &'_ mut R
impl<W: Write + ?Sized, '_> Write for &'_ mut W
[src]
impl<T> From<!> for T[src]
impl<T> From<T> for T[src]
impl<T, U> Into<U> for T where
U: From<T>, [src]
impl<T> ToOwned for T where
T: Clone, [src]
type Owned = TThe resulting type after obtaining ownership.
fn to_owned(&self) -> T[src]
fn clone_into(&self, target: &mut T)[src]
impl<T> ToString for T where
T: Display + ?Sized, [src]
impl<T, U> TryFrom<U> for T where
U: Into<T>, [src]
type Error = InfallibleThe type returned in the event of a conversion error.
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]
© 2010 The Rust Project Developers
Licensed under the Apache License, Version 2.0 or the MIT license, at your option.
https://doc.rust-lang.org/std/convert/enum.Infallible.html