Walkthrough

The changes refactor type instance and subclass checking in the virtual machine. The __instancecheck__ method on PyType now accepts a VirtualMachine argument and returns PyResult<bool>, delegating to a new real_is_instance method. The is_instance and is_subclass methods are enhanced to handle union types, reorder checks to match CPython, and avoid infinite recursion by using real_is_instance.

Changes

Sequence Diagram(s)

sequenceDiagram
    participant Caller
    participant PyType
    participant PyObject
    participant VirtualMachine

    Caller->>PyType: __instancecheck__(obj, vm)
    PyType->>PyObject: real_is_instance(self.as_object(), vm)
    PyObject->>VirtualMachine: (uses vm for context)
    PyObject-->>PyType: PyResult<bool>
    PyType-->>Caller: PyResult<bool>

sequenceDiagram
    participant Caller
    participant PyObject
    participant VirtualMachine

    Caller->>PyObject: is_instance(cls, vm)
    alt cls is a type
        PyObject->>PyObject: real_is_instance(cls, vm)
    else cls is a union
        loop each member in union
            PyObject->>PyObject: is_instance(member, vm)
        end
    else cls is a tuple
        loop each member in tuple
            PyObject->>PyObject: is_instance(member, vm)
        end
    else cls has __instancecheck__
        PyObject->>cls: __instancecheck__(self, vm)
    else
        PyObject->>PyObject: real_is_instance(cls, vm)
    end
    PyObject-->>Caller: PyResult<bool>

Poem

In the warren of types, a new path we define,
With real_is_instance, the checks are more fine.
No more recursion traps, nor confusion in sight,
Union and tuple types now handled just right.
With each hop and check, our logic aligns—
A rabbit’s delight in these elegant lines! 🐇

Configuration used: CodeRabbit UI
Review profile: CHILL
Plan: Pro

Reviewing files that changed from the base of the PR and between 1b40c45 and dd90515.

• Lib/test/test_isinstance.py (7 hunks)
• vm/src/builtins/type.rs (1 hunks)
• vm/src/protocol/object.rs (4 hunks)

• vm/src/builtins/type.rs
• vm/src/protocol/object.rs

Lib/**/*: Files in the Lib/ directory (Python standard library copied from CPython) should be edited very conservatively; modifications should be minimal and only to work around RustPython limitations.

📄 Source: CodeRabbit Inference Engine (.github/copilot-instructions.md)

List of files the instruction was applied to:

• Lib/test/test_isinstance.py

Lib/test/**/*: Tests in Lib/test often use markers such as '# TODO: RUSTPYTHON', 'unittest.skip("TODO: RustPython ")', or 'unittest.expectedFailure' with a '# TODO: RUSTPYTHON ' comment when modifications are made.
NEVER comment out or delete any test code lines except for removing '@unittest.expectedFailure' decorators and upper TODO comments.
NEVER modify test assertions, test logic, or test data in Lib/test files.
The only acceptable modifications to test files are: (1) removing '@unittest.expectedFailure' decorators and the upper TODO comments when tests actually pass, (2) adding '@unittest.expectedFailure' decorators when tests cannot be fixed.
When a test cannot pass due to missing language features, keep it as expectedFailure and document the reason.

📄 Source: CodeRabbit Inference Engine (.github/copilot-instructions.md)

List of files the instruction was applied to:

• Lib/test/test_isinstance.py

Learnt from: CR
PR: RustPython/RustPython#0
File: .github/copilot-instructions.md:0-0
Timestamp: 2025-06-26T12:52:11.109Z
Learning: When a test fails due to unsupported Python syntax or features, keep the test as '@unittest.expectedFailure' and document the reason, rather than modifying the test logic or data.

• GitHub Check: Run snippets and cpython tests (macos-latest)
• GitHub Check: Check Rust code with rustfmt and clippy
• GitHub Check: Run tests under miri
• GitHub Check: Run snippets and cpython tests on wasm-wasi
• GitHub Check: Run snippets and cpython tests (windows-latest)
• GitHub Check: Check the WASM package and demo
• GitHub Check: Run rust tests (windows-latest)
• GitHub Check: Run snippets and cpython tests (ubuntu-latest)
• GitHub Check: Run rust tests (macos-latest)
• GitHub Check: Run rust tests (ubuntu-latest)
• GitHub Check: Ensure compilation on various targets

Lib/test/test_isinstance.py (3)

355-356: Approve import localization improvement.

Moving the sys import from module level to function level improves code organization by placing the import close to its usage.

---

227-227: Verify that union type order change is necessary and doesn't alter test intent.

The order of types in the union was changed from (int | str | list[int] | float) to (float | str | list[int] | int). According to coding guidelines, test data modifications in Lib/test files should be avoided.

Please confirm this change is necessary to align with core implementation behavior and doesn't fundamentally alter the test's intent:

#!/bin/bash
# Description: Search for related changes in core isinstance/issubclass implementation
# Expected: Find evidence of union type ordering changes in core files

rg -A 5 -B 5 "union.*type.*order|type.*union.*order" 
ast-grep --pattern 'isinstance($_, $union_type)' 

---

313-313: Verify recursion depth parameter changes align with core implementation.

The support.infinite_recursion() calls now include a depth parameter of 25. This appears to accommodate core implementation changes but modifies test behavior.

Please verify these parameter changes are necessary:

#!/bin/bash
# Description: Check for changes in infinite_recursion support function and core recursion handling
# Expected: Find evidence of recursion depth changes in core or test support

rg -A 3 -B 3 "infinite_recursion.*25|recursion.*25"
ast-grep --pattern 'infinite_recursion($depth)'
rg "support\.infinite_recursion" --type py

Also applies to: 347-347

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