The implementation of the typing module is now more resilient to reference leaks in binary extension modules.
Previously, a reference leak in a typed C API-based extension module could leak internals of the typing module, which could in turn introduce leaks in essentially any other package with typed function signatures. Although the typing package is not the original source of the problem, such non-local dependences exacerbate debugging of large-scale projects, and the implementation was therefore changed to reduce harm by providing better isolation.