Incremental Type Migration Using Type Algebra

When a new set of types is introduced into a large software system, the task of retrofitting that system to take advantage of those types is generally cost-prohibitive. Existing automated type migration systems assume a one-to-one correspondence between old types and new types, making them unable to do partial migrations to more complex type sets. By using compiler-based migration tooling and an algebraically modeled type set, it is possible to use a small amount of manually seeded type information to automatically propagate the new types through a large monolithic C++ codebase. We demonstrate this technique by automatically generating 20k+ individual changes across a large industrial codebase of millions of lines of C++.