The types of `builtins.locals` and `types.FrameType.f_locals` aren't correct

builtins.locals and types.FrameType.f_locals are currently typed with dict[str, Any], which is incorrect:

• https://github.com/python/typeshed/blob/85a787bba3057f1df44188b4c815069d2d931557/stdlib/builtins.pyi#L1547

  Counterexample:

  from collections import UserDict
  
  class A(type):
      @classmethod
      def __prepare__(cls, name, bases): 
          return UserDict()
  
      def __new__(mcs, name, bases, namespace, /, **kw): 
          return super().__new__(mcs, name, bases, dict(namespace), **kw)
  
  class B(metaclass=A):
      assert isinstance(locals(), dict)  # AssertionError
  

• https://github.com/python/typeshed/blob/85a787bba3057f1df44188b4c815069d2d931557/stdlib/types.pyi#L585-L586

  Counterexample as a consequence of PEP 667 (Python >= 3.13):

  from inspect import currentframe
  
  def f():
      print(type(currentframe().f_locals))  # <class 'FrameLocalsProxy'>  (runtime type is `_collections_abc.framelocalsproxy`; not in `.pyi` stubs yet)
      assert isinstance(currentframe().f_locals, dict)  # AssertionError
  
  f()
  

However, I'm not sure what the actual type should be. From what I can gather, the type should implement a mapping interface, with a few (but not all?) MutableMapping methods (PEP 667 describes what these mutable mapping methods are for FrameType.f_locals, but I'm not sure what's exactly expected of builtins.locals()).

In addition, collections.abc.Mapping and collections.abc.MutableMapping themselves are unsuitable, because they're nominal types, although this could be fixed by defining a Protocol which looks like a Mapping.

So, what should the types of builtins.locals and types.FrameType.f_locals be?

Bắt đầu với các khai báo được tham chiếu trong stdlib/builtins.pyi và stdlib/types.pyi, sau đó đọc mô tả về FrameType.f_locals trong PEP 667 và so sánh với các ví dụ runtime trong issue. Công việc được xem là hoàn tất khi đã xác định và ghi lại các kiểu tương thích cho cả locals() và f_locals, bao gồm cả việc có cần một giao thức ánh xạ cấu trúc hay không.