Implement NativeWasmTypeInto for u32 and u64 with the js feature.

[kajacx]

Motivation

When using wasmer on the web (wasmer itself is compiled to WASM and then loads another WASM module) with the js feature, you cannot pass u32 and u64 as arguments from / to functions, because those types do not implement NativeWasmTypeInto.

Proposed solution

Implement NativeWasmTypeInto for u32 and u64.

Alternatives

You can, of course, cast your unsigned integers to signed integers, but it is kind of annoying. Example:

// Plugin:
#[no_mangle]
pub fn add_ten(value: u32) -> u32 {
    value + 10
}

// Host, current workaround:
let mut value: u32 = 50;
let add_ten = instance
    .exports
    .get_typed_function::<i32, i32>(&store, "add_ten")
    .unwrap();
value = take_u32.call(&mut store, value as i32).unwrap() as u32;

// Host, with proposed change:
let mut value: u32 = 50;
let add_ten = instance
    .exports
    .get_typed_function::<u32, u32>(&store, "add_ten")
    .unwrap();
value = take_u32.call(&mut store, value).unwrap();

Additional context

Not sure if implementing NativeWasmTypeInto for u8 / u16 / i8 / i16 makes sense in the same way, but that can be another feature request.

[syrusakbary]

That sounds good to me. Do you want to work on a PR @kajacx ?

[ptitSeb]

PR merged, closing the ticket.