> This is definitely not what Python is doing.

Maybe not by default but there is tooling that makes it work that way — that’s exactly how the python build system works at my company. I don’t know the details but when I “build” python code (creating bytecode pyc files) it produces compiler errors and fails to build if I e.g. try to pass an int to an f(x: str). This has usefully caught bugs before I ran some expensive/time-consuming scripts.

I guess you could say this doesn’t count as it’s a separate program doing the type checking but IMO there’s not a clear distinction between that and e.g. having a first type checking pass in the “same” compiler program.