ci: run `ty` and `zuban` on test suite

[MarcoGorelli]

It'll take a while until we can run them on the source code

But I'll like to prioritise running them on the test suite, and that tells us that/whether the public API works as intended

[dangotbanned]

Could we split this up into sub issues?

Idea

• Adopt more type checkers
  • Tracking: Adopt ty as an (additional) type checker #3409
    • Run ty on tests
      • I don't think this is worth doing yet, considering what's missing in (#3409)
      • But there has been a big improvement to (ty's spec-conformance results) 👏
    • Run ty on source
  • Adopt pyrefly
    • chore: run Pyrefly on tests #3563
    • Run pyrefly on source
      • I think this is worth exploring now since (Pyrefly 1.0.0) landed
  • Adopt zuban
    • Run zuban on tests
      • As a completionist, sure. Since it aims for mypy compatibility, it may not be that tricky?
      • But maybe we should wait until there's demand?
    • Run zuban on source

Related

I think that if you want to run 3x more type checkers in CI, then mypy and pyright need to be bumped to their most recent versions.

My thought being - if we can't keep these guys updated, how realistic is it to support all these emerging tools as well?

Note

I also want the shiny thing now, but these guys do need to take priority while they're more popular (and complete) 😔

mypy

• 1.15.0 (-15 months)
• 2.1.0

pyright

• 1.1.408 (-4 months)
• 1.1.409

[MarcoGorelli]

No reason not to work on these concurrently, if anything improving the situation for one type checker tends to improve it for others too

For pyright, there's a lot of errors related to NativeExpr not having __add__, __sub__ defined. My preference would to just add those to NativeExpr, and then relax the typing in _ibis (which isn't very useful anyway) https://github.com/narwhals-dev/narwhals/pull/2963/changes. Do you have an alternative suggestion?