Reject a fifth argument to property() - #8510

• Closes property() accepts a fifth positional argument instead of raising TypeError #8460
• This PR follows our AI policy

Summary

PropertyArgs declared a fifth positional-or-keyword field, name, so the derived arity was 0..=5 and property(None, None, None, None, None) built a property object with the fifth argument stored in the __name__ slot. CPython's property.__init__ is Argument Clinic generated with maxpos = 4 and the keyword list {fget, fset, fdel, doc}, so it rejects both that call and property(name='x').

AS-IS

>>> type(property(None, None, None, None, None))
<class 'property'>
>>> type(property(name='x'))
<class 'property'>

TO-BE

>>> property(None, None, None, None, None)
TypeError: expected at most 4 arguments, got 5
>>> property(name='x')
TypeError: Unexpected keyword argument name

(matching CPython, which raises TypeError for both; the message wording still comes from FuncArgs::bind rather than CPython's property() takes at most 4 arguments (5 given), which is a separate repo-wide difference)

Changes

• Remove the name field from PropertyArgs and the assignment that consumes it in Initializer::init, dropping the derived arity back to 0..=4.
• Drop the now-dead name: None initializer in clone_property_with and the unused PyStrRef import. The PyProperty name slot is untouched and is still filled by __set_name__ and the __name__ setter.
• Add regression tests in extra_tests/snippets/builtin_property.py for the five-positional-argument and name= keyword forms.

Test plan

Built and run on macOS aarch64 against upstream/main 525ba8cf0, using the CI feature set --no-default-features --features stdlib,importlib,stdio,encodings,sqlite,ssl-rustls-aws-lc,host_env.

• On an unpatched build of that commit both forms produced a property object; with the patch both raise TypeError. Four-argument construction, the getter/setter/deleter builders and __set_name__ still behave as before, and __set_name__ still fills the name slot.
• cargo run --release -- -m test test_property test_descr test_builtin: 331 run, 36 skipped, all pass.
• cargo test --workspace --exclude rustpython-capi --exclude rustpython_wasm --exclude rustpython-compiler-source --exclude rustpython-venvlauncher --features threading: 1107 pass, 0 fail. cargo test in crates/capi: 102 pass.
• extra_tests builtin snippets under RustPython: 66 of 67 pass, the new builtin_property.py cases among them. The one failure, builtin_thread.py, asserts _thread.TIMEOUT_MAX in [9223372036.0, 4294967.0] and my build reports 2147483648, which is an unrelated platform constant.
• cargo fmt --check clean, cargo clippy -p rustpython-vm --all-targets reports nothing on the changed file, and pre-commit run --files passes on both changed files.

I used Claude Code (claude-opus-5) to draft the analysis, the patch and this description; I reviewed the change and ran every command above myself.

Summary by CodeRabbit

• Bug Fixes
  • Corrected property handling so property names are managed consistently through standard name-assignment behavior.
  • property() now correctly rejects more than four positional arguments.
  • Unsupported name keyword arguments are now rejected.