`mypy` 1.20 and 1.20.1 break build of psygnal

[Czaki]

With mypy 1.20 and 1.20.1 the execution of uv run python -c "import psygnal; print('compiled:', psygnal._compiled)" ends with 139 error code.

Pinned mypy in #413

[mr-c]

Was this reported to the mypy devs? What is the issue number?

I was going to enable mypyc compiled builds of psygnal for Debian, and I ran into this issue.

[Czaki]

I don't reported it yet. I was waiting on @tlambert03 feedback, as I do not have experience with mypyc so don't know how to prepare some smaller example with bug reproduction.

[tlambert03]

I find that it's often hard to truly get to the bottom of mypyc issues. But more importantly, because it's only a build time and not a run time dependency, pinning to a specific version just for the sake of building is a perfectly acceptable solution for a project like this, with limited maintenance resources, until we have time (or sufficient other reason) to update to the latest mypyc and fix build issues. @mr-c, can you just use the same build time mypyc version that we use here when building for Debian? Or does it have to build on a broad range or the most recent version of mypyc?

[mr-c]

@tlambert03 I understand, and I empathize.

In Debian, all packages must be built using other official Debian packages. So we can't pull in any version of mypy, we have to use the version in the Debian archive. Alas we have upgraded mypy in the development release of Debian to 2.1.0. So I'll wait for this issue to be fixed before I enable mypyc compiled builds of psygnal in Debian.

(Theoretically we could revert the mypy Debian package to an older version, but that is messy and I don't think is warranted in this situation, since psygnal is already built without mypyc in Debian; so there is no regression there)

[tlambert03]

Ok thanks. I'll see what I can do to get it working on 2.10 again when I have a moment

[tlambert03]

@mr-c, fixed and working on mypy v2.1.0 now in #418

I'm curious: for Debian, do you need/prefer a new tag or versioned release of pysygnal? Or do you just pull this from main?