Gradual typing, proposed by Siek and Taha, is a framework to combine the benefits of static and dynamic typing. Under gradual typing, some parts of the program are type-checked at compile time, and the other parts are type-checked at run time. The main advantage of gradual typing is that a programmer can write a program rapidly without static type annotations in the beginning of development, then add type annotations as the development progresses and end up with a fully statically typed program; and all these development steps are carried out in a single language.

This paper reports work in progress on the introduction of gradual typing into class-based object-oriented programming languages with generics. In previous work, we have developed a gradual typing system for Feather-weight Java and proved that statically typed parts do not go wrong. After reviewing the previous work, we discuss issues raised when generics are introduced, and sketch a formalization of our solutions.