const expected_number = 123;

const foo = fn () s32 {
    return expected_number;
}

const Struct = struct{
    a: s32,
    handler: &const fn(s: &Struct) s32,

    const handler_function = fn (s: &Struct) s32 {
        return s.a;
    }
};

const Error = error{
    unexpected_result,
};

const main = fn () Error!void {
    var s = Struct{
        .a = expected_number,
        .handler = Struct.handler_function.&,
    };

    if (s.handler(s.&) - expected_number != 0) {
        return Error.unexpected_result;
    }
}