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author | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-28 14:29:10 +0000 |
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committer | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-28 14:29:10 +0000 |
commit | 2aa4a82499d4becd2284cdb482213d541b8804dd (patch) | |
tree | b80bf8bf13c3766139fbacc530efd0dd9d54394c /third_party/rust/unreachable/src/lib.rs | |
parent | Initial commit. (diff) | |
download | firefox-2aa4a82499d4becd2284cdb482213d541b8804dd.tar.xz firefox-2aa4a82499d4becd2284cdb482213d541b8804dd.zip |
Adding upstream version 86.0.1.upstream/86.0.1upstream
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
Diffstat (limited to 'third_party/rust/unreachable/src/lib.rs')
-rw-r--r-- | third_party/rust/unreachable/src/lib.rs | 77 |
1 files changed, 77 insertions, 0 deletions
diff --git a/third_party/rust/unreachable/src/lib.rs b/third_party/rust/unreachable/src/lib.rs new file mode 100644 index 0000000000..bb9b334312 --- /dev/null +++ b/third_party/rust/unreachable/src/lib.rs @@ -0,0 +1,77 @@ +#![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 + } + } +} + |