Rust stable 标准库是否使用了不稳定的特性？

Question

在 Rust 标准库中，you can see 像这样使用 const 泛型的实现：

#[stable(feature = "vec_from_array", since = "1.44.0")]
impl<T, const N: usize> From<[T; N]> for Vec<T> {
    #[cfg(not(test))]
    fn from(s: [T; N]) -> Vec<T> {
        <[T]>::into_vec(box s)
    }
    #[cfg(test)]
    fn from(s: [T; N]) -> Vec<T> {
        crate::slice::into_vec(box s)
    }
}

当我尝试在我的代码中做同样的事情时

impl<const N: usize> From<[u8; N]> for Binary {
    fn from(source: [u8; N]) -> Self {
        // Implementation available for $N <= 32.
        // Requires https://caniuse.rs/features/vec_from_array, avaiable since Rust 1.44.0.
        Self(source.into())
    }
}

我得到了错误

   --> packages/std/src/binary.rs:105:12
    |
105 | impl<const N: usize> From<[u8; N]> for Binary {
    |            ^
    |
    = note: see issue #74878 <https://github.com/rust-lang/rust/issues/74878> for more information

我正在使用 Rust 1.47.0。

这是否意味着 Rust 稳定的标准库是用不稳定的特性编译的？

Answer 1

是的，它使用不稳定的功能。 — Peter Hall

对于 Rust 1.47.0 的 liballoc（其中定义了 Vec），它使用 sixty or so unstable features。

另见：

• Is there a way to use unstable modules from Rust stable?
• Is there any way to get unstable features on the compiler versions in stable or beta?
• Up to date list of available nightly features?
• What is a crate attribute and where do I add it?
• Using Rust nightly in production
• Is it possible to compile one specific library with the nightly compiler and link it to a project that is compiled on stable?