Support Python 3.10 and ensure that new type hints works

[aaltat]

3.10 brings new way to present type hints. Make sure that example this works:

def func(arg: list[int] | list[str]):
    ...

[pekkaklarck]

Doesn't PLC just forward __annotations__ to RF? If yes, this ought to work with RF 4.1.1 and newer out of the box. Adding explicit tests is definitely a good idea anyway.

[aaltat]

Yes, it does forwards. If there is no changes in that area, things will most likely just work. But testing it out, is always a good idea.

[pekkaklarck]

PLC could actually convert x | y into (x, y) that RF handles as well. The benefit would be that then using x | y syntax would work also with older RF versions. I doubt that's worth the effort, though. People using Python 3.10 are likely to use latest RF version as well.

[aaltat]

I need to check, I think that is tested in unit level, but I used the Py3.10 in acceptance tests.

[pekkaklarck]

The x | y syntax requires Python 3.10 so no point testing with older. But it also requires RF 4.1.1 because x | y is actually types.UnionType and earlier RF versions don't support that. If PLC would convert types.UnionType to a tuple (just accessing its __args__ is enough), it would work also with earlier RF 4 versions. Implementation would be something like

try:
    from types import UnionType
except ImportError:
    UnionType = ()

...

if isintance(typ, UnionType):
    typ = typ.__args__

[aaltat]

PLC might actually do it already. Just need test and check how it goes in the code.