Question about specialization behaviour with Clone and Copy

Hey folks,

I was reading in the forum and found this topic which in turn led me to this topic where @steffahn posted this code snippet.

You can opt-in or opt-out the clone method of Clone via implementing Copy. I understand what this is good for but I don't understand why Rust "behaves" this way. Could anybody explain why this works this way? Is this behaviour documented anywhere?


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This is hinted at in docs for Clone.

It's implemented using specialization, which is an unstable/experimental feature that you can't normally use in stable Rust.

Also Clone is a "lang item", which means it has special-case implementations in the compiler.

In library/core/src/slice/


I see! :slight_smile: Thanks a lot!

See 1521-copy-clone-semantics - The Rust RFC Book for some background.

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