Developers who write code in a statically typed language are denied the ability to obtain dynamic feedback by executing their code during periods when it fails the static type checker. They are further confined to the static typing discipline during times in the development process where it does not yield the highest productivity. If they opt instead to use a dynamic language, they forgo the many benefits of static typing, including machine-checked documentation, improved correctness and reliability, tool support (such as for refactoring), and better runtime performance.