Macro clone 

macro_rules! clone {
    ($(,)?) => { ... };
    ($scope:ident . $name:ident $(, $($tail:tt)*)?) => { ... };
    (mut $scope:ident . $name:ident $(, $($tail:tt)*)?) => { ... };
    ($name:ident $(, $($tail:tt)*)?) => { ... };
    (mut $name:ident $(, $($tail:tt)*)?) => { ... };
}

Clone all the identifiers supplied as arguments.

clone!(x, y, z); will generate:

let x = x.clone();
let y = y.clone();
let z = z.clone();

This is useful for capturing variables by copy in closures. For example:

let closure = {
    clone!(x, y, z);
    move || {}
};

If you need a mutable clone, clone!(mut x) will generate:

let mut x = x.clone();

You can also clone struct members:

struct MyStruct {
    x: i32
}

impl MyStruct {
    fn clone_x(&self) {
        // This will generate `let x = self.x.clone();`
        clone!(self.x);
    }
}