Python多态重载故障

debugcn 发表于 Dev

卢卡·桑斯（Luca Sans S）

当尝试按照pep-3124 *中所述使用重载功能时，我遇到了一些麻烦：

[luca@artix tmp]$ more foo.py 
from overloading import overload
from collections import Iterable

def flatten(ob):
    """Flatten an object to its component iterables"""
    yield ob

@overload
def flatten(ob: Iterable):
    for o in ob:
        for ob in flatten(o):
            yield ob

@overload
def flatten(ob: basestring):
    yield ob
[luca@artix tmp]$ python3 foo.py 
/tmp/foo.py:2: DeprecationWarning: Using or importing the ABCs from 'collections' instead of from 'collections.abc' is deprecated since Python 3.3, and in 3.10 it will stop working
  from collections import Iterable
Traceback (most recent call last):
  File "/usr/lib/python3.9/site-packages/overloading.py", line 63, in overload
    return register(__registry[fname], func)
KeyError: '__main__.flatten'

在处理上述异常期间，发生了另一个异常：

Traceback (most recent call last):
  File "/tmp/foo.py", line 9, in <module>
    def flatten(ob: Iterable):
  File "/usr/lib/python3.9/site-packages/overloading.py", line 65, in overload
    __registry[fname] = overloaded(func)
  File "/usr/lib/python3.9/site-packages/overloading.py", line 151, in overloaded
    return register(dispatcher, func)
  File "/usr/lib/python3.9/site-packages/overloading.py", line 199, in register
    signature = get_signature(fn)
  File "/usr/lib/python3.9/site-packages/overloading.py", line 441, in get_signature
    types = tuple(normalize_type(type_hints.get(param, AnyType)) for param in parameters)
  File "/usr/lib/python3.9/site-packages/overloading.py", line 441, in <genexpr>
    types = tuple(normalize_type(type_hints.get(param, AnyType)) for param in parameters)
  File "/usr/lib/python3.9/site-packages/overloading.py", line 468, in normalize_type
    if not typing or not isinstance(type_, typing.TypingMeta) or type_ is AnyType:
AttributeError: module 'typing' has no attribute 'TypingMeta'
[luca@artix tmp]$

请注意，我卸载了键入模块。