fn each(vm: &mut VM, self_val: Value, args: &Args2) -> VMResult {
    args.check_args_num(0)?;
    let block = to_enum_id!(vm, self_val, args, IdentId::EACH);
    let aref = self_val.into_array();
    let mut i = 0;
    let f = vm.eval_block_map1(block);
    while i < aref.len() {
        f(vm, aref[i])?;
        i += 1;
    }
    Ok(self_val)
}
## instance method Array#each
- each {|item| .... } -> self
- each -> Enumerator

https://docs.ruby-lang.org/ja/latest/method/Array/i/each.html
ruruby/src/builtin/array.rs