function is lacking a `__signature__` attribute

PEP-362 specifies that in order to cache the signature of any function, it is possible for the user to set its __signature__ attribute.

Actual

This attribute is not set in the builtins module over at https://github.com/python/typeshed/blob/main/stdlib/builtins.pyi#L1009

As a result a typechecker might reject the following piece of code

from inspect import signature


def main():

    def f():
        pass

    f.__signature__ = signature(f)


if __name__ == "__main__":
    main()

e.g. with pyright I have a false positive

/Users/leogermond/Lab/python/signature/main.py
  /Users/leogermond/Lab/python/signature/main.py:9:7 - error: Cannot assign to attribute "__signature__" for class "function"
    Attribute "__signature__" is unknown (reportFunctionMemberAccess)
1 error, 0 warnings, 0 informations

Expected

I would the __signature__ attribute to be specified in the function class (with a special marker indicating it's optional?) of the builtins module. A type checker such as pyright could then infer that setting this attribute is possible and accept the piece of code given in example.

Beginnen Sie bei stdlib/builtins.pyi ungefähr in Zeile 1009 und prüfen Sie, wie die function class deklariert ist. Vergleichen Sie die angeforderte Unterstützung für signature mit PEP 362 und dem bereitgestellten Zuweisungsbeispiel und verifizieren Sie anschließend, dass ein Typechecker wie pyright sie akzeptiert, sobald die Stub-Änderung vollständig ist.