Language
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-* [Allow `concat_idents!` in type positions as well as in expression
- positions](https://github.com/rust-lang/rust/pull/33735).
* [`Copy` types are required to have a trivial implementation of `Clone`](https://github.com/rust-lang/rust/pull/33420).
[RFC 1521](https://github.com/rust-lang/rfcs/blob/master/text/1521-copy-clone-semantics.md).
* [Single-variant enums support the `#[repr(..)]` attribute](https://github.com/rust-lang/rust/pull/33355).