ICE: translating unsupported cast: alloc::rc::Rc<[i32]> in beta

[bluss]

Current beta release ICE's on trying to create a Rc<[i32]>.

Compile error in 1.0, works fine in nightly, so only beta channel.

use std::rc::Rc;

fn main() {
    let r = Rc::new([1, 2]) as Rc<[i32]>;
}

error: internal compiler error: translating unsupported cast: alloc::rc::Rc<[i32]> (cast_other) -> alloc::rc::Rc<[i32]> (cast_other)

[bluss]

cc @nrc

[nrc]

Given that this works on nightly, the question is whether we want to push the fix to beta (and I guess identifying the fix). I'd be happy not to - doesn't seem like enough pain to warrant jumping trains. But I could be swayed.

[bluss]

It's unfortunate that the feature is only halfway introduced in Rust 1.1 in that case. I understand this is not clearly tracked for the release at all.

[eddyb]

@nrc if the fix is backported, then #26038 should probably be included with it, as it allows Rc<RefCell<Unsized>> and friends.

[arielb1]

Closed as 1.1 was released.