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// Copyright 2017 Amanieu d'Antras
//
// Licensed under the Apache License, Version 2.0, <LICENSE-APACHE or
// http://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.
//! # unreachable
//! inlined from https://github.com/reem/rust-unreachable/
//!
//! An unreachable code optimization hint in stable rust, and some useful
//! extension traits for `Option` and `Result`.
//!
/// Hint to the optimizer that any code path which calls this function is
/// statically unreachable and can be removed.
///
/// Calling this function in reachable code invokes undefined behavior. Be
/// very, very sure this is what you want; often, a simple `panic!` is more
/// suitable.
#[inline]
pub unsafe fn unreachable() -> ! {
/// The empty type for cases which can't occur.
enum Void { }
let x: &Void = ::std::mem::transmute(1usize);
match *x {}
}
/// An extension trait for `Option<T>` providing unchecked unwrapping methods.
pub trait UncheckedOptionExt<T> {
/// Get the value out of this Option without checking for None.
unsafe fn unchecked_unwrap(self) -> T;
/// Assert that this Option is a None to the optimizer.
unsafe fn unchecked_unwrap_none(self);
}
/// An extension trait for `Result<T, E>` providing unchecked unwrapping methods.
pub trait UncheckedResultExt<T, E> {
/// Get the value out of this Result without checking for Err.
unsafe fn unchecked_unwrap_ok(self) -> T;
/// Get the error out of this Result without checking for Ok.
unsafe fn unchecked_unwrap_err(self) -> E;
}
impl<T> UncheckedOptionExt<T> for Option<T> {
unsafe fn unchecked_unwrap(self) -> T {
match self {
Some(x) => x,
None => unreachable()
}
}
unsafe fn unchecked_unwrap_none(self) {
if self.is_some() { unreachable() }
}
}
impl<T, E> UncheckedResultExt<T, E> for Result<T, E> {
unsafe fn unchecked_unwrap_ok(self) -> T {
match self {
Ok(x) => x,
Err(_) => unreachable()
}
}
unsafe fn unchecked_unwrap_err(self) -> E {
match self {
Ok(_) => unreachable(),
Err(e) => e
}
}
}
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