Enhancement: Improved type analysis perf by about 5% and reduced memory usage slightly by not formatting and logging diagnostic messages in cases where they are suppressed (e.g. argument type mismatches when doing overload matching).
Bug Fix: Fixed bug that affected dependency tracking of source files on platforms with case-insensitive file systems. In some cases, the case of paths differed, and the logic was treating these as separate files.
Enhancement: Added diagnostics for type variables that are used improperly as defined in PEP 484: 1) conflicting type variables that are used in nested generic class declarations, and 2) type variables that are used within annotations outside of a context in which they have meaning.
New Feature: Added support for "higher-order" type variables. You can now pass a generic function as an argument to another generic function, and the type var solver can solve the type variables for both at the same time.
New Feature: Added support for recursive type aliases.
Behavior Change: Updated the default Python version from 3.8 to 3.9. This is used only if it is not otherwise configured and there is no Python environment from which to determine the version.
Enhancement: Added checks for usage of certain built-in types that are defined as generic in the typeshed stubs but generate runtime exceptions if subscripted on older versions of Python (prior to 3.9). Such types need to be enclosed in quotes when used in annotations.