Signature for weakref __new__ incorrect?

[alicederyn]

The signature for weakref.ReferenceType.__new__ seems to be saying the arguments can be named:

typeshed/stdlib/_weakref.pyi

Line 23 in 52cf716

def __new__(cls, o: _T, callback: Callable[[ReferenceType[_T]], Any] | None = ...) -> Self: ...

If I try doing the following:

from weakref import ref

class Foo:
  pass

def callback(_):
  print("Deleted")

x = Foo()
y = ref(x, callback=callback)

pyright and mypy both seem happy with this, but in both Python 3.9 and 3.11 I get:

TypeError: ref() takes no keyword arguments

Should the parameters be renamed to __o and __callback to indicate they are positional-only?

[Akuli]

Yes, they should be named __o and __callback. I looked at the C code, and it uses PyArg_UnpackTuple whose documentation mentions this exact thing. PR welcome!

While you're at it, you could change the = ... to = None. In the C code, passing in None for the callback is handled the same as not giving a callback.