ecde1e1d3b
The easy parts of RFC 1859. (Just the trait and the lowering, none of the error message improvements nor the insta-stable impl for Option.)
71 lines
1.6 KiB
Rust
71 lines
1.6 KiB
Rust
// Copyright 2016 The Rust Project Developers. See the COPYRIGHT
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// file at the top-level directory of this distribution and at
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// http://rust-lang.org/COPYRIGHT.
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//
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// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
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// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
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// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
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// option. This file may not be copied, modified, or distributed
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// except according to those terms.
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#![feature(try_trait)]
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use std::ops::Try;
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enum MyResult<T, U> {
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Awesome(T),
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Terrible(U)
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}
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impl<U, V> Try for MyResult<U, V> {
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type Ok = U;
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type Error = V;
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fn from_ok(u: U) -> MyResult<U, V> {
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MyResult::Awesome(u)
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}
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fn from_error(e: V) -> MyResult<U, V> {
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MyResult::Terrible(e)
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}
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fn into_result(self) -> Result<U, V> {
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match self {
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MyResult::Awesome(u) => Ok(u),
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MyResult::Terrible(e) => Err(e),
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}
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}
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}
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fn f(x: i32) -> Result<i32, String> {
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if x == 0 {
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Ok(42)
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} else {
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let y = g(x)?;
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Ok(y)
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}
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}
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fn g(x: i32) -> MyResult<i32, String> {
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let _y = f(x - 1)?;
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MyResult::Terrible("Hello".to_owned())
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}
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fn h() -> MyResult<i32, String> {
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let a: Result<i32, &'static str> = Err("Hello");
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let b = a?;
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MyResult::Awesome(b)
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}
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fn i() -> MyResult<i32, String> {
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let a: MyResult<i32, &'static str> = MyResult::Terrible("Hello");
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let b = a?;
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MyResult::Awesome(b)
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}
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fn main() {
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assert!(f(0) == Ok(42));
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assert!(f(10) == Err("Hello".to_owned()));
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let _ = h();
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let _ = i();
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}
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