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#![cfg_attr(test, deny(warnings))]
#![deny(missing_docs)]
//! # unreachable
//!
//! An unreachable code optimization hint in stable rust, and some useful
//! extension traits for `Option` and `Result`.
//!
#![no_std]
extern crate void;
use core::mem;
/// 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() -> ! {
let x: &void::Void = mem::transmute(1usize);
void::unreachable(*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) {
match self {
Some(_) => unreachable(),
None => ()
}
}
}
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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