Add section about metaclass constructors - #2326
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Viicos
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Jul 31, 2026
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| Regardless of the evaluated return type of the implied metaclass call, a | ||
| :keyword:`class` statement defines a class, and type checkers should evaluate the | ||
| type of the bound name accordingly (``type[MyClass1]`` in the example above). | ||
| The implied metaclass call is evaluated only for the purpose of validating | ||
| its arguments. |
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This doesn't represent the runtime behavior:
class Meta(type):
def __new__(cls, *args, **kwargs):
return 1
class Class(metaclass=Meta): ...
Class
#> 1But all type checkers currently model this. It is pretty unusual for something like this to happen, and type checkers may rely on the assumption that a class statements always results in a type object.
Viicos
commented
Jul 31, 2026
| class MyClass4(other=1): # Type error: MyClass4.__init_subclass__() takes no keyword arguments | ||
| pass | ||
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| A metaclass :meth:`!__init__` method has no effect on this rule: when the |
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Perhaps type checkers could also enforce consistency between __init_subclass__() and __new__()/__init__() in some way?
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|
Apologies, I keep facing a Github bug opening PRs on the upstream repo. Meant to open this on my fork. |
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