Add #[derive(Clone, Debug)] to all web-sys types

[alexcrichton]

They're all cloneable and debuggable!

[fitzgen]

🎉

[chinedufn]

Something that comes to mind here:

let mut elem = document.get_element_by_id("id");
let mut elem2 = elem1.clone();

One might expect that elem2 and elem1 each own their own copy of the underling #id element here, but that wouldn't be the case.

Mutating elem1 would mutate elem2.

Should you even be allowed to clone, what's the use case here (haven't thought through the cases here so I'm actually just asking ha)?

If so... should there instead be a let elem2 = web_sys::clone(elem1) to make this more clear?

[fitzgen]

@chinedufn it's the same as something like Rc<RefCell<...>>: shared ownership with interior mutability. If you think about it, JS things are always shared with JS land, and JS is not bound by the mutability xor aliasing that Rust usually follows, so everything in JS is implicitly mutable. Given that, I think it makes sense.

[chinedufn]

Makes sense!