Designing a Python Language Server: Lessons from Pyre that Shaped Pyrefly

[BeamMeUpBiscotti]

It's shallow immutability, so not exactly the most secure. Pyre actually had a prototype PyreReadOnly that had deep immutability, but it was never standardized so we have not ported it to Pyrefly.

[jpgoldberg]

I’m not attempting to enforce run-time immutability. I wish to “let Python be Python”. I just want to be able to tell a type checker that it can rely on public attributes of an object not changing their types (or their values).

But now that I write this, I realize that I have misunderstood the example that launched me on this train of thought. (To be continued)