maximum semantic analysis iteration count reached with importing two dataclasses modules

[NiklasRosenstein]

Crash Report

Deferral trace:
    databind.core.dataclasses_test:35
    databind.core.dataclasses_test:35
    [...]
    databind.core.dataclasses_test:35
    databind.core.dataclasses_test:35
src/databind/core/dataclasses_test.py: error: INTERNAL ERROR: maximum semantic analysis iteration count reached
Found 1 error in 1 file (errors prevented further checking)

My project has a databind.core.dataclasses module which is supposed to be used as a drop-in replacement for dataclasses. In the unittests dataclasses_test, I import both of these modules but doing that crashes Mypy.

I haven't been able to come up with a smaller scenario to reproduce the issue.

Traceback

--show-traceback does not give any additional information other than what is shown above.

To Reproduce

1. Clone https://github.com/NiklasRosenstein/databind.git and check out 74c5c6e
2. Change directory into databind.core
3. Install mypy pytest types-setuptools
4. Run mypy src and not how there are no errors
5. Open src/databind/core/dataclasses_test.py and insert import dataclasses at the top of the file
6. Run mypy src again (you will see the error)

Your Environment

• Mypy version used: 0.910
• Mypy command-line flags: n/a
• Mypy configuration options from mypy.ini (and other config files): n/a
• Python version used: 3.9.6
• Operating system and version: osx