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bpo-39481: Implementation for PEP 585 (#18239)

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This implements things like `list[int]`,
which returns an object of type `types.GenericAlias`.
This object mostly acts as a proxy for `list`,
but has attributes `__origin__` and `__args__`
that allow recovering the parts (with values `list` and `(int,)`.

There is also an approximate notion of type variables;
e.g. `list[T]` has a `__parameters__` attribute equal to `(T,)`.
Type variables are objects of type `typing.TypeVar`.
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Guido van Rossum 2020-04-07 09:50:06 -07:00 • committed by GitHub
parent 9cc3ebd7e0
commit 48b069a003
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30 changed files with 830 additions and 53 deletions
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7
Lib/typing.py
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@ -26,7 +26,7 @@ import operator
import re as stdlib_re # Avoid confusion with the re we export.
import sys
import types
from types import WrapperDescriptorType, MethodWrapperType, MethodDescriptorType
from types import WrapperDescriptorType, MethodWrapperType, MethodDescriptorType, GenericAlias
# Please keep __all__ alphabetized within each category.
__all__ = [
@ -180,7 +180,8 @@ def _collect_type_vars(types):
for t in types:
if isinstance(t, TypeVar) and t not in tvars:
tvars.append(t)
if isinstance(t, _GenericAlias) and not t._special:
if ((isinstance(t, _GenericAlias) and not t._special)
or isinstance(t, GenericAlias)):
tvars.extend([t for t in t.__parameters__ if t not in tvars])
return tuple(tvars)
@ -947,7 +948,7 @@ _TYPING_INTERNALS = ['__parameters__', '__orig_bases__', '__orig_class__',
_SPECIAL_NAMES = ['__abstractmethods__', '__annotations__', '__dict__', '__doc__',
'__init__', '__module__', '__new__', '__slots__',
'__subclasshook__', '__weakref__']
'__subclasshook__', '__weakref__', '__class_getitem__']
# These special attributes will be not collected as protocol members.
EXCLUDED_ATTRIBUTES = _TYPING_INTERNALS + _SPECIAL_NAMES + ['_MutableMapping__marker']