Introspection: generate nested classes for complex enums

[Tpt]

No description provided.

[Tpt]

We need the two "flavors" because for complex enum variants the first one will be Enum_Variant and the second one just Variant

[Tpt]

Note the the PyTypeInfo::TYPE_HINT value for variants is currently wrong. Will fix it in a follow-up.

[davidhewitt]

This syntax technically isn't valid:

class MixedComplexEnum:
    @final
    class Empty(MixedComplexEnum): ...

    @final
    class Nothing(MixedComplexEnum): ...

gives

Traceback (most recent call last):
  File "<python-input-2>", line 1, in <module>
    class MixedComplexEnum:
    ...<4 lines>...
        class Nothing(MixedComplexEnum): ...
  File "<python-input-2>", line 3, in MixedComplexEnum
    class Empty(MixedComplexEnum): ...
                ^^^^^^^^^^^^^^^^
NameError: name 'MixedComplexEnum' is not defined

... I wonder, is something like the below better?

class MixedComplexEnum:
    Empty: Final[type[Empty]] = ...
    Nothing: Final[type[Nothing]] = ...
    
@final
class Empty(MixedComplexEnum): ...

@final
class Nothing(MixedComplexEnum): ...

[Tpt]

Interesting. Missed that. Thanks!

... I wonder, is something like the below better?

We would need to tweak it a bit to make sure Empty is not exposed as one of the member of the module. Happily there is a hack for that. I will experiment around it.

[Tpt]

I just tested with Mypy and this syntax error does not prevent it to parse the stubs.

I added the implementation of enums method to this MR.

If it's fine with you I would leave this issue for later (adding it to the introspection TODO issue) and focus on having mypy green on the pytests module (we are nearly there, with this MR and #5758 I only get misc and override errors that should be not too hard to fix). WDYT?

[davidhewitt]

Makes sense to me, happy to defer until when we know it's actually a problem (if it ever is).