74 lines
1.7 KiB
Rust
74 lines
1.7 KiB
Rust
|
// Copyright 2016 The Rust Project Developers. See the COPYRIGHT
|
||
|
|
// file at the top-level directory of this distribution and at
|
||
|
|
// http://rust-lang.org/COPYRIGHT.
|
||
|
|
//
|
||
|
|
// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
|
||
|
|
// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
|
||
|
|
// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
|
||
|
|
// option. This file may not be copied, modified, or distributed
|
||
|
|
// except according to those terms.
|
||
|
|
|
||
|
|
#![feature(question_mark, question_mark_carrier)]
|
||
|
|
|
||
|
|
use std::ops::Carrier;
|
||
|
|
|
||
|
|
enum MyResult<T, U> {
|
||
|
|
Awesome(T),
|
||
|
|
Terrible(U)
|
||
|
|
}
|
||
|
|
|
||
|
|
impl<U, V> Carrier for MyResult<U, V> {
|
||
|
|
type Success = U;
|
||
|
|
type Error = V;
|
||
|
|
|
||
|
|
fn from_success(u: U) -> MyResult<U, V> {
|
||
|
|
MyResult::Awesome(u)
|
||
|
|
}
|
||
|
|
|
||
|
|
fn from_error(e: V) -> MyResult<U, V> {
|
||
|
|
MyResult::Terrible(e)
|
||
|
|
}
|
||
|
|
|
||
|
|
fn translate<T>(self) -> T
|
||
|
|
where T: Carrier<Success=U, Error=V>
|
||
|
|
{
|
||
|
|
match self {
|
||
|
|
MyResult::Awesome(u) => T::from_success(u),
|
||
|
|
MyResult::Terrible(e) => T::from_error(e),
|
||
|
|
}
|
||
|
|
}
|
||
|
|
}
|
||
|
|
|
||
|
|
fn f(x: i32) -> Result<i32, String> {
|
||
|
|
if x == 0 {
|
||
|
|
Ok(42)
|
||
|
|
} else {
|
||
|
|
let y = g(x)?;
|
||
|
|
Ok(y)
|
||
|
|
}
|
||
|
|
}
|
||
|
|
|
||
|
|
fn g(x: i32) -> MyResult<i32, String> {
|
||
|
|
let _y = f(x - 1)?;
|
||
|
|
MyResult::Terrible("Hello".to_owned())
|
||
|
|
}
|
||
|
|
|
||
|
|
fn h() -> MyResult<i32, String> {
|
||
|
|
let a: Result<i32, &'static str> = Err("Hello");
|
||
|
|
let b = a?;
|
||
|
|
MyResult::Awesome(b)
|
||
|
|
}
|
||
|
|
|
||
|
|
fn i() -> MyResult<i32, String> {
|
||
|
|
let a: MyResult<i32, &'static str> = MyResult::Terrible("Hello");
|
||
|
|
let b = a?;
|
||
|
|
MyResult::Awesome(b)
|
||
|
|
}
|
||
|
|
|
||
|
|
fn main() {
|
||
|
|
assert!(f(0) == Ok(42));
|
||
|
|
assert!(f(10) == Err("Hello".to_owned()));
|
||
|
|
let _ = h();
|
||
|
|
let _ = i();
|
||
|
|
}
|