Actionable comments posted: 0

crates/vm/src/builtins/type.rs (1)

1798-1808: Handle edge case when class name consists entirely of underscores.

When class_name consists only of underscores (e.g., _, __, ___), trim_start_matches('_') returns an empty string. This causes the code to produce "___x" for a name like "__x" in such a class, which diverges from CPython's behavior—CPython does not mangle names in classes whose names consist only of underscores and returns the original name unchanged.

Add a check after stripping the leading underscores:

 fn mangle_name(class_name: &str, name: &str) -> String {
     // Only mangle names starting with __ and not ending with __
     if !name.starts_with("__") || name.ends_with("__") || name.contains('.') {
         return name.to_string();
     }
     // Strip leading underscores from class name
     let class_name = class_name.trim_start_matches('_');
+    if class_name.is_empty() {
+        return name.to_string();
+    }
     format!("_{}{}", class_name, name)
 }

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Reviewing files that changed from the base of the PR and between 98fff96 and 8718dc4.

• Lib/test/datetimetester.py is excluded by !Lib/**
• Lib/test/test_contextlib.py is excluded by !Lib/**
• Lib/test/test_contextlib_async.py is excluded by !Lib/**
• Lib/test/test_dataclasses.py is excluded by !Lib/**
• Lib/test/test_decimal.py is excluded by !Lib/**
• Lib/test/test_fractions.py is excluded by !Lib/**
• Lib/test/test_functools.py is excluded by !Lib/**
• Lib/test/test_os.py is excluded by !Lib/**
• Lib/test/test_statistics.py is excluded by !Lib/**
• Lib/test/test_typing.py is excluded by !Lib/**

• crates/vm/src/builtins/object.rs (1 hunks)
• crates/vm/src/builtins/type.rs (4 hunks)
• crates/vm/src/stdlib/typevar.rs (2 hunks)

📄 CodeRabbit inference engine (.github/copilot-instructions.md)

**/*.rs: Follow the default rustfmt code style by running cargo fmt to format Rust code
Always run clippy to lint Rust code (cargo clippy) before completing tasks and fix any warnings or lints introduced by changes
Follow Rust best practices for error handling and memory management
Use the macro system (pyclass, pymodule, pyfunction, etc.) when implementing Python functionality in Rust

Files:

• crates/vm/src/builtins/object.rs
• crates/vm/src/stdlib/typevar.rs
• crates/vm/src/builtins/type.rs

Learnt from: CR
Repo: RustPython/RustPython PR: 0
File: .github/copilot-instructions.md:0-0
Timestamp: 2025-11-29T12:17:28.606Z
Learning: Applies to **/*.rs : Use the macro system (`pyclass`, `pymodule`, `pyfunction`, etc.) when implementing Python functionality in Rust

Applied to files:

• crates/vm/src/builtins/type.rs

• GitHub Check: Run snippets and cpython tests (windows-latest)

crates/vm/src/builtins/type.rs (3)

310-317: LGTM! Correct HAS_DICT inheritance from MRO.

The change from checking only the first base to checking any base in the MRO aligns with CPython's behavior. If any base class in the MRO has HAS_DICT, the subclass should inherit it too since it needs to support instance dictionaries from any base.

---

1188-1213: LGTM! Name mangling correctly applied to slot-backed member descriptors.

The implementation properly:

1. Extracts the class name before processing slots
2. Applies mangling to each slot attribute name
3. Uses the mangled name consistently for both the PyMemberDef and the attribute key on the type

This matches CPython's behavior where __x in __slots__ becomes _ClassName__x as the actual attribute.

---

1233-1246: LGTM! Correct conditional addition of __dict__ descriptor.

The updated condition ensures the __dict__ descriptor is only added when:

1. The base is not type (type subclasses inherit __dict__ from type)
2. The class has the HAS_DICT flag (meaning __slots__ was not defined, or __dict__ was explicitly in __slots__)

This correctly implements the __slots__ xor __dict__ semantics.

crates/vm/src/builtins/object.rs (1)

69-79: LGTM! Dict creation now driven by HAS_DICT flag.

The change correctly ties instance dict creation to the HAS_DICT flag rather than a hardcoded type check. This ensures:

• Classes with __slots__ (no __dict__ in slots) → no instance dict
• Classes without __slots__ or with __dict__ in __slots__ → instance dict created

This aligns with the type initialization changes and properly implements Python's __slots__ semantics.

crates/vm/src/stdlib/typevar.rs (3)

3-3: LGTM!

The Context import is required for the new __slots__ method signature.

---

975-978: LGTM! Empty __slots__ on Generic matches CPython.

Defining __slots__ = () on Generic prevents instances from having an instance dictionary, which is the expected behavior for this typing construct. Using #[pyattr] correctly defines this as a class attribute.

---

986-988: LGTM! __init_subclass__ delegation to typing module.

The implementation correctly delegates to _generic_init_subclass in the typing module, consistent with the existing __class_getitem__ pattern and CPython's behavior for handling Generic subclass initialization.