Let's start with the CPython hierarchy (name => text repr):

• PyDescrObject - common fields for all descriptors: d_type, d_name, d_qualname. Is extended by:
• • PyMethodDescrObject => <method '%V' of '%s' objects>
• • PyMemberDescrObject => <member '%V' of '%s' objects>
• • PyGetSetDescrObject => <attribute '%V' of '%s' objects>
• • • Embeds PyGetSetDef
• • PyWrapperDescrObject => <slot wrapper '%V' of '%s' objects>

Our structure is nothing near. It consists of:

• trait SlotDescriptor, which defines __get__. It is used for all descriptors like methods, properties
• PyGetSet which is used for @property declarations, it also defines __set__ and __delete__
• PyBuiltinMethod, right now it looks like PyMethodDescrObject and PyCMethodObject at the same time

My plan (I might be wrong):

1. Create PyDescrObject with d_type, d_name, d_qualname fields (names would be without prefixes)
2. Create PyWrapperDescrObject and PyMemberDescrObject with PyDescrObject field
3. Create PyGetSetDescrObject with PyDescrObject and PyGetSet fields
4. Add PyDescObject field to PyBuiltinMethod, do we really need an extra wrapper here?
5. Change new_getset and new_readonly_getset methods in ctx to use new descriptor types and new names
6. Change how we create builtin methods
7. Add proper repr to new types to match CPython, refs #2811 and #2809
8. Document our descriptor hierarchy and compare it with CPython

Any other things I've missed?

It doesn't look important, but PyGetSet and PyProperty(@property) are different. PyGetSet is a sort of internal property, but their detailed behaviours are not the same.

About plans:

1. Sounds perfect
2. is this #2842?
3. great
4. If CPython does, let's just go like that. nothing to lose. So PyMethodDescrObject here with additional field vectorcall(what's this?).
5. good. but what you meant by 'new names'?
6. no idea yet

I think #2842 is just type.__new__ not looking for a __slots__ present. __slot__ entries turn into members if I remember correctly we just don't currently do it.

@youknowone

2. Yes, sounds related. I will keep this in mind. Does RustPython have any optimizations (similar to CPython) right now for __slots__ attribute access?
3. Ok. vectorcall is an optimization for faster calling: https://www.python.org/dev/peps/pep-0590/ I think it safe to leave this out of scope for now
4. New names that do not reference getset, because it is going to be "more internal"
5. It will be required if we change how PyBuiltinMethod works in 4.

2. No, we don't have any optimizations for __slots__.
   4/5. I think we just need new_getset. We only use it to create classes and modules. The name just need to show we are creating a getset object. The annotation name is even #[pyproperty] which is not property at all, but to fit mental model for people.