src/librustc_data_structures/ptr_key.rs

// Copyright 2018 The Rust Project Developers. See the COPYRIGHT
// file at the top-level directory of this distribution and at
// http://rust-lang.org/COPYRIGHT.
//
// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
// http://www.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::{hash, ptr};
use std::ops::Deref;

/// A wrapper around reference that compares and hashes like a pointer.
/// Can be used as a key in sets/maps indexed by pointers to avoid `unsafe`.
#[derive(Debug)]
pub struct PtrKey<'a, T: 'a>(pub &'a T);

impl<'a, T> Clone for PtrKey<'a, T> {
    fn clone(&self) -> Self { *self }
}

impl<'a, T> Copy for PtrKey<'a, T> {}

impl<'a, T> PartialEq for PtrKey<'a, T> {
    fn eq(&self, rhs: &Self) -> bool {
        ptr::eq(self.0, rhs.0)
    }
}

impl<'a, T> Eq for PtrKey<'a, T> {}

impl<'a, T> hash::Hash for PtrKey<'a, T> {
    fn hash<H: hash::Hasher>(&self, hasher: &mut H) {
        (self.0 as *const T).hash(hasher)
    }
}

impl<'a, T> Deref for PtrKey<'a, T> {
    type Target = T;

    fn deref(&self) -> &Self::Target {
        self.0
    }
}