> I also don't get the performance argument: Type hints aren't evaluated at runtime, so whether code has them or not shouldn't matter for performance.

Type hints actually are evaluated at runtime, since they're part of the syntax tree. They just aren't checked for correctness, so the (small, but sometimes non-negligible) amount of parsing overhead they add is essentially lost performance.

The correct way would be to do conditional imports that are only performed while typechecking in this case. But I'd expect the issue to happen often.

    from __future__ import annotations
    from typing import TYPE_CHECKING

    if TYPE_CHECKING:
        import mymodule

    def myfunc(arg: mymodule.MyType) -> bool:
        return bool(arg)

    from __future__ import annotations

Most runtime type checking modules I am aware of support

  from __future__ import annotations

When I had complained earlier, Guido didn't give 2 shits, although it broke typedload, a library I wrote that is very similar to pydantic, when pydantic didn't exist.

So I know what I am saying

There are applications where all the unnecessary abstractions might make sense but those are the exception not the rule.

I hate this spin to somehow make it about not trusting developers to do their job right. As if it was an insult to test for correctness. Imagine skipping pre-flight checks for accomplished pilots, or load calculations for renowned bridge engineers.

This hubris of some software developers assuming to be hyper-correct geniuses really alienates me.