Guido van Rossum <[email protected]> added the comment:
When PEP 585 was discussed and implemented we did not expect people to care as
much about runtime types as they did.
I already explained that making list['Node'] incorporate a ForwardRef instance
is unrealistic (we'd have to reimplement ForwardRef in C first).
It might be possible to change get_type_hints() to recognize strings, and
deprecate ForwardRef altogether. But I suspect that that would break something
else, since ForwardRef is documented (I had intended it to remain an internal
detail but somehow it got exposed, I don't recall why).
Please stop asking why the decision was made (it sounds rather
passive-aggressive to me) and start explaining the problem you are having in a
way that we can actually start thinking about a solution.
I have boiled down the original example to a slightly simpler one (dataclasses
are a red herring):
>>> from typing import get_type_hints, List
>>> class N:
... c1: list["N"]
... c2: List["N"]
...
>>> N.__annotations__
{'c1': list['N'], 'c2': typing.List[ForwardRef('N')]}
>>> get_type_hints(N)
{'c1': list['N'], 'c2': typing.List[__main__.N]}
The key problem here is that the annotation list['N'] is not expanded to
list[N]. What can we do to make get_type_hint() produce list[N] instead here?
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<https://bugs.python.org/issue41370>
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