Trait FromResidual

pub trait FromResidual<R = <Self as Try>::Residual> {
    // Required method
    fn from_residual(residual: R) -> Self;
}

🔬This is a nightly-only experimental API. (try_trait_v2 #84277)

Used to specify which residuals can be converted into which crate::ops::Try types.

Every Try type needs to be recreatable from its own associated Residual type, but can also have additional FromResidual implementations to support interconversion with other Try types.

Required Methods

fn from_residual(residual: R) -> Self

🔬This is a nightly-only experimental API. (try_trait_v2 #84277)

Constructs the type from a compatible Residual type.

This should be implemented consistently with the branch method such that applying the ? operator will get back an equivalent residual: FromResidual::from_residual(r).branch() --> ControlFlow::Break(r). (The residual is not mandated to be identical when interconversion is involved.)

Examples

#![feature(try_trait_v2)]
use std::ops::{ControlFlow, FromResidual};

assert_eq!(Result::<String, i64>::from_residual(Err(3_u8)), Err(3));
assert_eq!(Option::<String>::from_residual(None), None);
assert_eq!(
    ControlFlow::<_, String>::from_residual(ControlFlow::Break(5)),
    ControlFlow::Break(5),
);

Dyn Compatibility

This trait is not dyn compatible.

In older versions of Rust, dyn compatibility was called "object safety", so this trait is not object safe.

Implementors

impl<B, C> FromResidual<ControlFlow<B, Infallible>> for ControlFlow<B, C>

impl<T> FromResidual<Option<Infallible>> for Option<T>

impl<T> FromResidual<Yeet<()>> for Option<T>

impl<T, E, F: From<E>> FromResidual<Result<Infallible, E>> for Result<T, F>

impl<T, E, F: From<E>> FromResidual<Result<Infallible, E>> for Poll<Option<Result<T, F>>>

impl<T, E, F: From<E>> FromResidual<Result<Infallible, E>> for Poll<Result<T, F>>

impl<T, E, F: From<E>> FromResidual<Yeet<E>> for Result<T, F>