Hands-On Concurrency with Rust

Option

Let's examine Option<T>. We've already discussed Option<T> in this chapter; that it's subject to null pointer optimization on account of its empty None variant in particular. Option is as simple as you might imagine, being defined in src/libcore/option.rs:

#[derive(Clone, Copy, PartialEq, PartialOrd, Eq, Ord, Debug, Hash)]
#[stable(feature = "rust1", since = "1.0.0")]
pub enum Option<T> {
    /// No value
    #[stable(feature = "rust1", since = "1.0.0")]
    None,
    /// Some value `T`
    #[stable(feature = "rust1", since = "1.0.0")]
    Some(#[stable(feature = "rust1", since = "1.0.0")] T),
}

As is often the case with Rust internals, there are a great deal of flags around to control when and where new features land in which channel and how documentation ...