Common Lisp was the first language I'm aware of with optional typing. In theory, what you're saying is true. In practice there's a lot of pressure to ship the w

Common Lisp was the first language I'm aware of with optional typing. In theory, what you're saying is true. In practice there's a lot of pressure to ship the working prototype, and retrofitting types on it later doesn't actually happen. The result was a reputation for being slow. (This was back when computers were slow enough that the overhead of being dynamic was pretty painful.)