Incorrect attribute access for functions nested inside methods

[bzoracler]

Bug Report, To Reproduce, & Actual Behaviour

The first parameter of a function, nested inside a method, can inappropriately access certain attributes on the method's bound instance. See mypy Playground:

from typing_extensions import reveal_type

class A:
    class B: ...
    
    def method(self) -> None:
        def f2(arg: object) -> None:
            reveal_type(arg.B)  # N: Revealed type is "def () -> __main__.A.B"
        f2(3)  # Runtime error

The accessible items are static references to modules, classes, and type aliases. This is due to some implementation details in semanal.py:

mypy/mypy/semanal.py

Lines 6091 to 6097 in 30b2a2d

	elif isinstance(base.node, Var) and self.type and self.function_stack:
	# check for self.bar or cls.bar in method/classmethod
	func_def = self.function_stack[-1]
	if not func_def.is_static and isinstance(func_def.type, CallableType):
	formal_arg = func_def.type.argument_by_name(base.node.name)
	if formal_arg and formal_arg.pos == 0:
	type_info = self.type

Expected Behavior

            reveal_type(arg.B)  # E: "object" has no attribute "B"  [attr-defined]

Your Environment

• Mypy version used: 1.19.1, master