Cannot determine type of "userlist"

Bug Report

Unexpected error Cannot determine type of "userlist". Needs a cyclic import to happen.

To Reproduce

foo.py

import bar

class Foo:
    def __init__(self) -> None:
        self.view_selector = object()

bar.py

from foo import Foo

class ServerView:
    def __init__(self) -> None:
        print(ChannelView().userlist)
        self.view_id = str(Foo().view_selector)

class ChannelView:
    def __init__(self) -> None:
        print(ServerView().view_id)
        self.userlist = object()

Expected Behavior

no error, or an error that does not confusingly go away when I delete a seemingly unrelated line of code

Actual Behavior

$ python3 -m mypy foo.py bar.py
bar.py:5: error: Cannot determine type of "userlist"
Found 1 error in 1 file (checked 2 source files)

Your Environment

• Mypy version used: master (053a1beb94ee4e5b3260725594315d1b6776e42f)
• Mypy command-line flags: none
• Mypy configuration options from mypy.ini (and other config files): none
• Python version used: doesn't matter, why do you ask?
• Operating system and version: is a weird question to ask. I am tired of answering this question. But I guess it could be useful in some other issue.

まず、提供された循環インポートの例に対して python3 -m mypy foo.py bar.py を実行し、userlist エラーを期待される動作と比較します。mypy が foo.py と bar.py の Foo、ServerView、ChannelView の定義をどのように解析するかを追跡します。完了の条件は、例で紛らわしい Cannot determine type of "userlist" エラーが発生しなくなるか、より明確な診断が報告されることです。