Enum core::convert::Infallible  
1.34.0 · source · pub enum Infallible {}Expand description
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`
    }
}§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:
… 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 to have 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.
Trait Implementations§
1.34.0 · source§impl Clone for Infallible
 
impl Clone for Infallible
source§fn clone(&self) -> Infallible
 
fn clone(&self) -> Infallible
1.0.0 · source§fn clone_from(&mut self, source: &Self)
 
fn clone_from(&mut self, source: &Self)
source. Read more1.34.0 · source§impl Debug for Infallible
 
impl Debug for Infallible
1.34.0 · source§impl Display for Infallible
 
impl Display for Infallible
1.8.0 · source§impl Error for Infallible
 
impl Error for Infallible
source§fn description(&self) -> &str
 
fn description(&self) -> &str
1.30.0 · source§fn source(&self) -> Option<&(dyn Error + 'static)>
 
fn source(&self) -> Option<&(dyn Error + 'static)>
1.34.0 · source§impl From<!> for Infallible
 
impl From<!> for Infallible
1.34.0 · source§impl From<Infallible> for TryFromIntError
 
impl From<Infallible> for TryFromIntError
source§fn from(x: Infallible) -> TryFromIntError
 
fn from(x: Infallible) -> TryFromIntError
1.36.0 · source§impl From<Infallible> for TryFromSliceError
 
impl From<Infallible> for TryFromSliceError
source§fn from(x: Infallible) -> TryFromSliceError
 
fn from(x: Infallible) -> TryFromSliceError
1.44.0 · source§impl Hash for Infallible
 
impl Hash for Infallible
1.34.0 · source§impl Ord for Infallible
 
impl Ord for Infallible
1.34.0 · source§impl PartialEq for Infallible
 
impl PartialEq for Infallible
source§fn eq(&self, _: &Infallible) -> bool
 
fn eq(&self, _: &Infallible) -> bool
self and other values to be equal, and is used
by ==.1.34.0 · source§impl PartialOrd for Infallible
 
impl PartialOrd for Infallible
1.0.0 · source§fn le(&self, other: &Rhs) -> bool
 
fn le(&self, other: &Rhs) -> bool
self and other) and is used by the <=
operator. Read more