Type and Effect Systems for Dynamically Changing Code - DRAFT CORRECTIONS, DO NOT DISTRIBUTE

We extend type and effect analyses to permit dynamically changing effects and dynamically changing code in multi-threaded systems with shared resources. We guarantee that after a well typed modification a set of threads will have the specified desired effects and will continue to safely use the resources. We prove the key properties of subject reduction and fidelity (safety) for our general system. We provide an application of our system: dynamic software updating for a multi-threaded asynchronous message passing system. We show how key safety properties from session typing follow from the properties of our general system