A library for cloning trait objects.

Instability

This library depends on an undocumented detail of fat pointer layouts.

For that reason, this library is intentionally marked as unstable.

Example

Making a cloneable user-defined trait

```rust use cloneintobox::{CloneIntoBox, CloneIntoBoxExt};

// Make the trait a subtrait of CloneIntoBox pub trait MyTrait: CloneIntoBox { fn hello(&self) -> String; }

// Manually implement Clone using clone_into_box impl Clone for Box { fn clone(&self) -> Self { // Use (self) to prevent ambiguity. // Otherwise you may run into a mysterious stack overflow. (self).cloneintobox() } }

[derive(Debug, Clone)]

struct Foo(String);

impl MyTrait for Foo { fn hello(&self) -> String { format!("Hello, {}!", self.0) } }

fn main() { let x: Box = Box::new(Foo(String::from("John"))); asserteq!(x.hello(), "Hello, John!"); let y = x.clone(); asserteq!(y.hello(), "Hello, John!"); } ```

Making a cloneable variant of an existing trait

```rust use cloneintobox::{CloneIntoBox, CloneIntoBoxExt};

// Use a "new trait" pattern to create a trait for ExistingTrait + CloneIntoBox pub trait FnClone: Fn() -> String + CloneIntoBox {} impl String + CloneIntoBox + ?Sized> FnClone for T {}

// Manually implement Clone using clone_into_box impl Clone for Box { fn clone(&self) -> Self { // Use (self) to prevent ambiguity. // Otherwise you may run into a mysterious stack overflow. (self).cloneintobox() } }

fn main() { let name = String::from("John"); let x: Box = Box::new(move || format!("Hello, {}!", name)); asserteq!(x(), "Hello, John!"); let y = x.clone(); asserteq!(y(), "Hello, John!"); } ```