| #![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 |
| } |
| } |
| } |
| |