Allow only typeguard lower than 3.x.x version

[knyazer]

Hi Patrick,

I noticed that in pyproject.toml there is no constraint on the highest allowed version of typeguard, eventhough it looks like there should be. PEP 508 explains how does version notation work, and thus I just introduced this constraint.

[knyazer]

I am not exactly sure what all the effects might be, but I think the main effect is reduced amount of wrong-typeguard-version problems when doing pip install jaxtyping, since now the typeguard of the correct version will be installed.

[patrick-kidger]

LGTM! This is worthwhile, agreed.

[MaximilienLC]

Hi y'all, typeguard < 3 dates back 2 years or so. Might be better to bound it to a more recent date to avoid conflicts. First example: pygls

jaxtyping 0.2.23 depends on typeguard<3 and >=2.13.3
pygls 1.1.1 depends on typeguard<4.0.0 and >=3.0.0

[patrick-kidger]

Unfortunately, typeguard v3 or v4 are known to have some bugs; these issues are triggered by jaxtyping in particular. There's some back-and-forth on the topic here: agronholm/typeguard#353

To be honest, my impression is that later versions of typeguard have started doing things that are unlikely to be broadly compatible with the ecosystem at large -- things like setting typing.TYPE_CHECKING=True, or re-parsing the AST of modules after they've been imported. Hence why we pin to an older version.

(As JAX's JIT compilation means that the overhead from runtime type-checking is unimportant, I'm starting to contemplate writing my own simple-and-slow-but-correct runtime type checker just to solve this issue.)