Since this PR was written, the PSF has decided to go on a different direction than from __future__ import annotations. You can read about it here. Right now they consider moving towards PEP 649 instead.

Unfortunately, I think we might should drop this PR. @davidism , would love to hear your opinion on it.

from __future__ import annotations will continue to work as it does, and any change will still result in deferred evaluation of annotations.

Updated to use modern typing syntax and features. Both MyPy and PyRight support using modern syntax with older Pythons when using from __future__ import annotations.

• Remove typing_extensions where possible.
• Use shorthand union syntax | instead of Union and Optional.
• Use generic types from built-ins, collections, collections.abcandcontextlib`.
• Quote TypeVar bound and cast types to avoid runtime evaluation of generics and unions.