tests/ui/consts/const-try.rs


1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40

//@ known-bug: #110395

// Demonstrates what's needed to make use of `?` in const contexts.

#![crate_type = "lib"]
#![feature(try_trait_v2)]
#![feature(const_trait_impl, effects)]
#![feature(const_try)]
#![allow(incomplete_features)]

use std::ops::{ControlFlow, FromResidual, Try};

struct TryMe;
struct Error;

impl const FromResidual<Error> for TryMe {
    fn from_residual(residual: Error) -> Self {
        TryMe
    }
}

impl const Try for TryMe {
    type Output = ();
    type Residual = Error;
    fn from_output(output: Self::Output) -> Self {
        TryMe
    }
    fn branch(self) -> ControlFlow<Self::Residual, Self::Output> {
        ControlFlow::Break(Error)
    }
}

const fn t() -> TryMe {
    TryMe?;
    TryMe
}

const _: () = {
    t();
};