Lazy circular import with bottom import cannot determine type if the module name is alphabetically after the base class module

[nelsyeung]

To Reproduce

mkdir mypyissue
cd mypyissue
touch __init__.py a.py b.py c.py circular.py py.typed

a.py:

import typing_extensions as t
from .b import Base
class A(Base):
    def run(self) -> None:
        t.reveal_type(self._v)

b.py:

import typing as t
class Base:
    def __init__(self, v: t.Optional[str] = None) -> None:
        from .circular import circular
        self._v: t.Final = v or circular.v
from .a import A
from .c import C

c.py:

import typing_extensions as t
from .b import Base
class C(Base):
    def run(self) -> None:
        t.reveal_type(self._v)

circular.py

from .b import Base
class Circular:
    @property
    def v(self) -> str:
        return "value"
circular = Circular()

Expected Behavior

self._v to have the correct type for all children. Or at least consistently fail rather than now where somehow the module name matters.

Actual Behavior

c.py:5: error: Cannot determine type of "_v"  [has-type]
c.py:5: note: Revealed type is "Any"
a.py:5: note: Revealed type is "builtins.str"
Found 1 error in 1 file (checked 5 source files)

Notice that a.py has the correct type but not c.py.

Your Environment

• Mypy version used: mypy 1.15.0 (compiled: yes)
• Mypy command-line flags: Nothing
• Mypy configuration options from mypy.ini (and other config files): Nothing
• Python version used: 3.9.19

Additional notes

• Pyright works in this case.
• The first character of the file name is important. In this case, since Base is in b.py, any module named after b alphabetically (i.e., c, d, e, etc...) will fail to determine the type but not a.py. E.g., if b.py was instead d.py, then both a.py and c.py will have the correct type.
• The bottom imports and the Base import in circular.py are needed to reproduce this. If removed, this works.

Workaround

Explicitly add the type:

self._v: t.Final[str] = v or circular.v