python >=3.8: cmath functions should accept any object with __index__

[Akuli]

runtime:

akuli@akuli-desktop:/tmp$ cat asd.py
class Foo:
    def __index__(self):
        return 1
akuli@akuli-desktop:/tmp$ python3.7 -c 'import cmath, asd; cmath.sin(asd.Foo())'
Traceback (most recent call last):
  File "<string>", line 1, in <module>
TypeError: must be real number, not Foo
akuli@akuli-desktop:/tmp$ python3.8 -c 'import cmath, asd; cmath.sin(asd.Foo())'
akuli@akuli-desktop:/tmp$ 

(The error message is wrong, the functions also accept complex numbers)

Stub:

typeshed/stdlib/cmath.pyi

Line 11 in 05cc30b

_C = Union[SupportsFloat, SupportsComplex, complex]

typeshed/stdlib/cmath.pyi

Line 30 in 05cc30b

def sin(__z: _C) -> complex: ...