Clone trait that is object-safe

This crate provides a Clone trait that can be used in trait objects, and a clone_box function that can clone any sized or dynamically sized implementation of Clone. Types that implement the standard library's [std::clone::Clone] trait are automatically usable this way.

The signature of clone_box is:

rust fn clone_box<T>(t: &T) -> Box<T> where T: ?Sized + objekt::Clone

Example

```rust trait MyTrait: objekt::Clone { fn recite(&self); }

impl MyTrait for String { fn recite(&self) { println!("{} ♫", self); } }

fn main() { let line = "The slithy structs did gyre and gimble the namespace";

// Build a trait object holding a String.
// This requires String to implement MyTrait and std::clone::Clone.
let x: Box<MyTrait> = Box::new(String::from(line));

x.recite();

// The type of x2 is a Box<MyTrait> cloned from x.
let x2 = objekt::clone_box(&*x);

x2.recite();

} ```

This crate includes a macro for concisely implementing impl std::clone::Clone for Box<MyTrait> in terms of objekt::clone_box.

```rust // As before. trait MyTrait: objekt::Clone { /* ... */ }

objekt::clonetraitobject!(MyTrait);

// Now data structures containing Box can derive Clone:

[derive(Clone)]

struct Container { trait_object: Box, } ```

License

<sup>Licensed under either of Apache License, Version 2.0 or MIT license at your option.</sup>

<sub>Unless you explicitly state otherwise, any contribution intentionally submitted for inclusion in this crate by you, as defined in the Apache-2.0 license, shall be dual licensed as above, without any additional terms or conditions.</sub>