Enum std::convert::Infallible 1.34.0[−][src]
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` } }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:
pub type Infallible = !;Run
… 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 {}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 Clone for Infallible
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impl Clone for Infallible
[src]pub fn clone(&self) -> Infallible
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pub fn clone_from(&mut self, source: &Self)
1.0.0[src]
impl Error for Infallible
1.8.0[src]
impl Error for Infallible
1.8.0[src]impl From<!> for Infallible
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impl From<!> for Infallible
[src]pub fn from(x: !) -> Infallible
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impl From<Infallible> for TryFromIntError
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impl From<Infallible> for TryFromIntError
[src]pub fn from(x: Infallible) -> TryFromIntError
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impl From<Infallible> for TryFromSliceError
1.36.0[src]
impl From<Infallible> for TryFromSliceError
1.36.0[src]pub fn from(x: Infallible) -> TryFromSliceError
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impl Hash for Infallible
1.44.0[src]
impl Hash for Infallible
1.44.0[src]impl Ord for Infallible
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impl Ord for Infallible
[src]impl PartialEq<Infallible> for Infallible
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impl PartialEq<Infallible> for Infallible
[src]impl PartialOrd<Infallible> for Infallible
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impl PartialOrd<Infallible> for Infallible
[src]pub fn partial_cmp(&self, _other: &Infallible) -> Option<Ordering>
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#[must_use]pub fn lt(&self, other: &Rhs) -> bool
1.0.0[src]
#[must_use]pub fn le(&self, other: &Rhs) -> bool
1.0.0[src]
#[must_use]pub fn gt(&self, other: &Rhs) -> bool
1.0.0[src]
#[must_use]pub fn ge(&self, other: &Rhs) -> bool
1.0.0[src]
impl Copy for Infallible
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impl Eq for Infallible
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Auto Trait Implementations
impl RefUnwindSafe for Infallible
impl Send for Infallible
impl Sync for Infallible
impl Unpin for Infallible
impl UnwindSafe for Infallible
Blanket Implementations
impl<T> Borrow<T> for T where
T: ?Sized,
[src]
impl<T> Borrow<T> for T where
T: ?Sized,
[src]pub fn borrow(&self) -> &TⓘNotable 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: Future + Unpin + ?Sized, type Output = <F as Future>::Output;impl<R: Read + ?Sized> Read for &mut Rimpl<W: Write + ?Sized> Write for &mut W
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Notable 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: Future + Unpin + ?Sized, type Output = <F as Future>::Output;impl<R: Read + ?Sized> Read for &mut Rimpl<W: Write + ?Sized> Write for &mut W
impl<T> BorrowMut<T> for T where
T: ?Sized,
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impl<T> BorrowMut<T> for T where
T: ?Sized,
[src]pub fn borrow_mut(&mut self) -> &mut TⓘNotable 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: Future + Unpin + ?Sized, type Output = <F as Future>::Output;impl<R: Read + ?Sized> Read for &mut Rimpl<W: Write + ?Sized> Write for &mut W
[src]
Notable 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: Future + Unpin + ?Sized, type Output = <F as Future>::Output;impl<R: Read + ?Sized> Read for &mut Rimpl<W: Write + ?Sized> Write for &mut W