Arc<str> can't be bincoded

[nalply]

Arc<str> can't be bincoded with bincode 2. See code and error message below. Arc<&str> works though. Link to gist at bottom.

use std::sync::Arc;
use bincode;

fn main() {
  let val: Arc<str> = std::sync::Arc::from("Example String");
  let config = bincode::config::standard();
  let encoded = bincode::encode_to_vec(val, config).unwrap();


  for byte in encoded {
    print!(" {byte:02x}");
  }
  println!();
}

compiled on rustc 1.61.0-nightly (58f11791a 2022-03-17) on MacOS gives:

error[E0277]: the size for values of type `str` cannot be known at compilation time
  --> minimal_example/src/main.rs:7:40
   |
7  |   let encoded = bincode::encode_to_vec(val, config).unwrap();
   |                 ---------------------- ^^^ doesn't have a size known at compile-time
   |                 |
   |                 required by a bound introduced by this call
   |
   = help: the trait `Sized` is not implemented for `str`
   = note: required because of the requirements on the impl of `Encode` for `Arc<str>`
note: required by a bound in `encode_to_vec`
  --> /Users/nalp/.cargo/registry/src/github.ghproxy.top-1ecc6299db9ec823/bincode-2.0.0-rc.1/src/features/impl_alloc.rs:42:25
   |
42 | pub fn encode_to_vec<E: enc::Encode, C: Config>(val: E, config: C) -> Result<Vec<u8>, EncodeError> {
   |                         ^^^^^^^^^^^ required by this bound in `encode_to_vec`

https://gist.github.com/nalply/c29385f0046ca03ae0f3a687dfeb24d1

[VictorKoenders]

This is part of a larger issue where we might have to split Decode and BorrowDecode into separate traits. Work is being done in #526 but it's going to be a slow process.

[VictorKoenders]

We can implement Encode for Arc<str>, however we cannot implement Decode for Arc<str> as this would conflict with Decode for Arc<T>.

Edit: I'm wrong and it should all work in 2.0.0-rc.2