voa

Check whether a type implements a trait

use instance::{define_interface, Interface};

define_interface!(TypeSize);
trait TypeSize {
    fn type_size(&self) -> usize;
}

struct WasmI32(i32);
struct WasmI64(i64);
impl TypeSize for WasmI32 {
    fn type_size(&self) -> usize {
        4
    }
}

fn main() {
    let v1 = WasmI32(0);
    let object = v1.cast();
    println!("{:?}", object.map(|v| v.meta_data())); // 4
    let v2 = WasmI64(0);
    let object = Interface::<dyn TypeSize>::recast(&v2);
    println!("{:?}", object.map(|v| v.meta_data())); // None
}