Add as_void_ptr helper method to &T

[jdm]

There are lots of places where we write code like &foo *const _ as *const _ (like here, here, and here) where the receiver code expects a *const c_void. This code would be clearer if we could use foo.as_void_ptr() where as_void_ptr is a trait method that's implemented for every type T.

[KiChjang]

Would the T in this case be T: DomStruct? I don't think we can globally define methods for every type yet...

[jdm]

We can define a trait and import it everywhere that it's needed.

[KiChjang]

Ah, I see what this is. Create a trait:

pub trait AsVoidPtr {
    fn as_void_ptr(&self) -> *const c_void
}

And then implementing this trait on every foo struct where we use the &foo as *const _ as *const _ pattern.

[jdm]

I'm pretty sure we can implement the trait for a generic type T, rather than specific implementations for types we care about.

[highfive]

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[mckaymatt]

@highfive: assign me

[highfive]

Hey @mckaymatt! Thanks for your interest in working on this issue. It's now assigned to you!

[mckaymatt]

@jdm Is this what you are talking about?

use std::os::raw::c_void;

trait AsVoidPtr {
    fn as_void_ptr(&self) -> *const c_void;
}

impl<T> AsVoidPtr for T {
    fn as_void_ptr(&self) -> *const c_void {
        // &*self as *const _ as *const c_void
        &*self as *const _ as *const c_void
    }
}

I'm thinking I would put it someplace like components/script/lib.rs? Or maybe it's own crate components/pointer. Or components/script/dom/bindings?

[jdm]

dom/bindings/utils.rs would make sense to me. You should not need the &* in &*self, though, and it couldn't hurt to replace the _ with T.