invalid type: floating point after math operations

[lastmjs]

Describe the bug

I have been using the new JsValue to_json functionality and I'm running into some issues. I am dealing with numbers in JS that should be valid integers, whether they be u32, i32, etc. boa seems to have issues with to_json because it is converting them into Rationals for an unknown reason. This might be related to #1961.

To Reproduce

fn main() {
    println!("get_u32: {}", get_u32());
}

fn get_u32() -> u32 {
    let mut context = boa_engine::Context::default();

    let return_value = context.eval(r#"
        1000000 - 500
    "#).unwrap();

    serde_json::from_value(return_value.to_json(& mut context).unwrap()).unwrap()
}

Expected behavior

This should print get_u32: 999500 and should not error out. Instead I get this error:

thread 'main' panicked at 'called `Result::unwrap()` on an `Err` value: Error("invalid type: floating point `999500`, expected u32", line: 0, column: 0)', src/main.rs:12:74

Build environment (please complete the following information):

• OS: Ubuntu 20.04
• Version: latest main
• Target triple: wasm32-unknown-unknown or x86_64-unknown-linux-gnu
• Rustc version: rustc 1.58.1 (db9d1b20b 2022-01-20)

Additional context

It seems like certain math operations are causing a Rust representation of Rational unnecessarily.

[jedel1043]

This is pretty unrelated to #1961 :)
We currently convert to f64 when any operation between i32 is executed, but we should be checking whether the result is representable by a i32, or else, convert both operands to f64 and execute the operation. I'll work on this while we discuss #1961

[RageKnify]

I sort of mentioned this before in #1147

[Razican]

I am dealing with numbers in JS that should be valid integers, whether they be u32, i32, etc. boa seems to have issues with to_json because it is converting them into Rationals for an unknown reason.

Just to explain this. The reason is that there is no such thing as an "integer" type in JavaScript. All numeric types are 64-bit floating point numbers. So this should never work like this: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#number_type

[lastmjs]

Yes thank you. This goes back to my latest comment here: #1961 (comment)

I would just like some kind of JsValue::into to easily convert my JsValues to another type.

let my_u32: u32 = my_js_value.into();

If we could have something like that for arbitrary structs, enums, etc that would be excellent. Does this functionality exist?