Ties between Parametrically Polymorphic Type Systems and Finite Control Automata

We present a correspondence and bisimulation between variants of parametrically polymorphic type systems and variants of finite control automata, such as FSA, PDA, tree automata and Turing machine. Within this correspondence we show that two recent celebrated results on automatic generation of fluent API are optimal in certain senses, present new results on the studied type systems, formulate open problems, and present potential software engineering applications, other than fluent API generation, which may benefit from judicious use of type theory.