Move PyList Python methods and operators to Py<PyList> - #8848

Follow-up to #8819, same rules applied to list. Four commits.

Move PyList Python methods and operators to Py

• Py<PyList>::borrow_vec() / borrow_vec_mut() are the views. PyList::__len__() is removed; its callers read borrow_vec().len().

• The Python interface of list moves from the PyList payload to a #[pyclass] impl Py<PyList> block, registered through with(Py, ...):

  • every #[pymethod] (append, extend, insert, clear, copy, __sizeof__, reverse, __reversed__, __getitem__, count, index, pop, remove, sort) and #[pyclassmethod] __class_getitem__
  • the operators __add__ (which replaces concat()), __iadd__, __mul__, __imul__, __setitem__, __delitem__, __contains__ and inplace_concat

  The #[pyclass] impl PyList block keeps only with(...) and flags(...).

• PyList keeps the helpers that work on the payload: _getitem, _setitem, _delitem, repeat, irepeat and sort, which sorted() and dir() also call on a PyList value before it becomes an object. Py<PyList> reaches them through the payload field. The mapping and sequence slots call the Py<PyList> operators.

• GenericAlias.__dir__ works on the PyList value returned by vm.dir(), so it appends through borrow_vec_mut() and checks membership with mut_contains().

• Deref is unchanged and behavior is unchanged.

Rename Traverse::clear to clear_refs

Traverse::clear becomes clear_refs, and MaybeTraverse::try_clear becomes try_clear_refs. Before this, list.clear() on a PyRef<PyList> resolved to the Traverse trait method instead of Py<PyList>::clear. The derive macros and every existing impl are renamed. try_clear_obj, HAS_CLEAR and #[pyclass(clear)] are unchanged.

Expose the PyList_* operations on Py

Only the operations that have a PyList_* counterpart are pub on Py<PyList>. Names follow pyo3's PyListMethods.

• The sort pymethod is now implemented by sort_with_options().
• get_slice, set_slice and del_slice clamp both bounds to the list.
• set_item, set_slice and del_slice drop the replaced elements after the list lock is released.
• The capi PyList_Size, PyList_Append, PyList_Insert, PyList_Reverse and PyList_AsTuple call these methods.
• A unit test covers the new methods.

Call the Py methods from the remaining capi PyList_* functions

PyList_GetItemRef, PyList_SetItem, PyList_GetSlice, PyList_SetSlice and PyList_Sort now call the Py<PyList> methods. Their behavior changes to match the C API:

• PyList_GetSlice and PyList_SetSlice clamp negative bounds to 0 instead of counting them from the end of the list.
• PyList_SetSlice collects the new items before taking the list lock, so a list can be assigned into itself.
• PyList_GetItemRef and PyList_SetItem raise IndexError without the index in the message.
• PyList_Sort sorts the list directly instead of calling its sort method.
• PyList_SetItem still appends when the index equals the length and the list has spare capacity, as after PyList_New.

New capi tests cover negative bounds, deleting a slice, and assigning a list into itself.

🤖 Generated with Claude Code

Summary by CodeRabbit

• Bug Fixes
  • Corrected C API list indexing so negative indices are treated as out of range.
  • Improved list slicing behavior, including deletion and replacing a list’s contents with itself.
• Improvements
  • Updated list operations to provide consistent behavior across Python-facing and C API usage, with expanded coverage for list mutations and sorting.