On 2/2/2021 8:37 PM, Caleb Donovick wrote:
The discussion around PEP 649 got me thinking about what I believe is
the largest downside to PEP 563: the inability to evaluate annotations
created with closures. While this is in general unavoidable, if
the type is ever referenced in an annotated function (including as an
annotation) it should be resolvable via `__closure__`.
For example:
```
from __future__ import annotations
import typing
def gen(T):
def f(x: T):
y: T = ...
return f
f = gen(int)
nonlocal_vars = {
var : cell.cell_contents
for var, cell in zip(f.__code__.co_freevars, f.__closure__)
}
assert typing.get_type_hints(f, localns=nonlocal_vars) == {'x': int}
```
I would just open a PR to have `get_type_hints` attempt to resolve
closure variables by default. However, this would require an update to
PEP 563 and I don't know what the protocol is there.
Once a PEP is accepted and implemented, the PEP document itself is
frozen and not updated. The Python language and docs and the CPython
implementation are still subject to what is hopefully further progress.
You are free to open an thread on python-ideas list or an issue on bpo,
optionally with a PR, or both. It would be good to reference the PEP
and note whether this idea appears there or not. Further discussion of
the idea itself would depend on whether is was a rejected alternative, a
deferred addition, or just mentioned.
A speculative PR for an idea not yet accepted in principle may be
rejected but may help gain acceptance.
PS: I don't use type hints yet and have not much opinion about about
your idea (it naively seems plausible), so the above is a generic answer.
--
Terry Jan Reedy
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