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ilevkivskyigvanrossum
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Kill __subclasscheck__ (#283)
This PR: - Fixes #136 - Fixes #133 - Partially addresses #203 (fixes the isinstance part, and multiple inheritance, still typing.Something is not a drop-in replacement for collections.abc.Something in terms of implementation). - Also fixes http://bugs.python.org/issue26075, http://bugs.python.org/issue25830, and http://bugs.python.org/issue26477 - Makes almost everything up to 10x faster. - Is aimed to be a minimalistic change. I only removed issubclass tests from test_typing and main changes to typing are __new__ and __getitem__. The idea is to make most things not classes. Now _ForwardRef(), TypeVar(), Union[], Tuple[], Callable[] are not classes (i.e. new class objects are almost never created by typing). Using isinstance() or issubclass() rises TypeError for almost everything. There are exceptions: Unsubscripted generics are still OK, e.g. issubclass({}, typing.Mapping). This is done to (a) not break existing code by addition of type information; (b) to allow using typing classes as a replacement for collections.abc in class and instance checks. Finally, there is an agreement that a generic without parameters assumes Any, and Any means fallback to dynamic typing. isinstance(lambda x: x, typing.Callable) is also OK. Although Callable is not a generic class, when unsubscribed, it could be also used as a replacement for collections.abc.Callable. The first rule for generics makes isinstance([], typing.List) possible, for consistency I also allowed isinstance((), typing.Tuple). Finally, generics should be classes, to allow subclassing, but now the outcome of __getitem__ on classes is cached. I use an extended version of functools.lru_cache that allows fallback to non-cached version for unhashable arguments.
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