src/unreachable.rs

// 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.

use std::hint::unreachable_unchecked;

/// 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_unchecked(),
        }
    }

    unsafe fn unchecked_unwrap_none(self) {
        if self.is_some() {
            unreachable_unchecked()
        }
    }
}

impl<T, E> UncheckedResultExt<T, E> for Result<T, E> {
    unsafe fn unchecked_unwrap_ok(self) -> T {
        match self {
            Ok(x) => x,
            Err(_) => unreachable_unchecked(),
        }
    }

    unsafe fn unchecked_unwrap_err(self) -> E {
        match self {
            Ok(_) => unreachable_unchecked(),
            Err(e) => e,
        }
    }
}