Derive Macro GetType 

#[derive(GetType)]
{
    // Attributes available to this derive:
    #[idx]
    #[get_type]
}

• #[get_type(idx = 1)] in fields
• #[get_type(flatten)] for unnamed structs
• #[get_type(with_type(Type))] for named struct fields
• #[get_type(unimplemented)] for named struct fields
• #[get_type(custom("name", &[Typ::Bool, Typ::Str]))] for named struct fields