> Those are unstable, so you have to use another attribute opt in to using them. But you can absolutely put them on your own type.
They are, as their name suggests, deliberately perma-unstable rust compiler (rustc) only. You technically can use them in types anyway (and if you go look at the nook crate, I have, that's why I know so much about them) but because they're perma-unstable that's a terrible idea and you clearly shouldn't use this.
Even if they were just unstable, (like say const traits) you can only do this in nightly Rust, it's not available in stable Rust and as the people who'd decided "Oh, const traits, those sound great, I'll just use them and eventually they'll be stable" discovered, nope, that's not what we meant when we told you they're not stable. We meant what we said, and those traits just plain went away (probably they'll be back eventually, but maybe not).
But I agree the stuff that's "just" unstable isn't compiler magic, after all the intent is, even if it doesn't always work out, that those features eventually get stabilized. These are perma-unstable because they're compiler internals. They are magic.
They are, as their name suggests, deliberately perma-unstable rust compiler (rustc) only. You technically can use them in types anyway (and if you go look at the nook crate, I have, that's why I know so much about them) but because they're perma-unstable that's a terrible idea and you clearly shouldn't use this.
Even if they were just unstable, (like say const traits) you can only do this in nightly Rust, it's not available in stable Rust and as the people who'd decided "Oh, const traits, those sound great, I'll just use them and eventually they'll be stable" discovered, nope, that's not what we meant when we told you they're not stable. We meant what we said, and those traits just plain went away (probably they'll be back eventually, but maybe not).
But I agree the stuff that's "just" unstable isn't compiler magic, after all the intent is, even if it doesn't always work out, that those features eventually get stabilized. These are perma-unstable because they're compiler internals. They are magic.