I'd like type annotations to be used to optimise performance. After all, if it has been statically verified that a particular variable is always an instance of

I'd like type annotations to be used to optimise performance. After all, if it has been statically verified that a particular variable is always an instance of class X, why not use that to optimise code? This is an argument for type annotations to be integrated into every dynamically typed language, rather than tacked on via an external tool.