Encoding Featherweight Java with assignment and immutability using the Coq proof assistant

We develop a mechanized proof of Featherweight Java with Assignment and Immutability in the Coq proof assistant. This is a step towards more machine-checked proofs of a non-trivial type system. We used object immutability close to that of IGJ [9]. We describe the challenges of the mechanisation and the encoding we used inside of Coq.