Allow ABCMeta in PyType_FromMetaclass

Feature or enhancement

Proposal:

Currently Python 3.14 will deny any metaclass that implements tp_new, which ABCMeta does.

My suggestion is to add special logic in PyType_FromMetaclass that if the metaclass is ABCMeta or a subtype uses its tp_new instead of custom that it adds the abstract flag, and calls the method that calculates abstractmethods attribute.

Currently there is logic in CPython to mark native methods as abstract.

Has this already been discussed elsewhere?

No response given

Links to previous discussion of this feature:

No response

首先定位 PyType_FromMetaclass 以及將原生方法標記為抽象方法的現有邏輯。追蹤 ABCMeta 及其子型別如何處理 tp_new，以及如何計算 abstractmethods。完成的標準是接受與 ABCMeta 相容的中繼類別，同時保留抽象標誌和計算行為。