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typing __parameters__ __type_params__ by youknowone · Pull Request #5909 · RustPython/RustPython

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Walkthrough

This update extends the compiler and runtime to support default values for type parameters and automatic insertion of generic base classes in line with PEP 695. It introduces new bytecode instructions, intrinsic function handling, synchronization for type parameter defaults, and updates class construction to manage type parameter attributes and defaults.

Changes

File(s) Change Summary
compiler/codegen/src/compile.rs Enhanced type parameter compilation to support defaults per PEP 695; updated class definition logic for automatic generic base insertion and deferred symbol table popping.
compiler/core/src/bytecode.rs Added enums for intrinsic functions, new bytecode instructions (CallIntrinsic1, CallIntrinsic2), and updated stack effect and instruction display logic.
vm/src/builtins/genericalias.rs Added subscript_generic function to create a GenericAlias from type parameters, mimicking CPython’s internal behavior.
vm/src/frame.rs Implemented execution for new intrinsic call instructions; added methods for intrinsic dispatch; minor fix in ParamSpec handling.
vm/src/stdlib/builtins.rs Modified __build_class__ to set both __type_params__ (cloned) and new __parameters__ attributes on classes for typing compatibility.
vm/src/stdlib/typevar.rs Changed evaluate_default fields to use PyMutex for thread-safe access; added set_typeparam_default function; adjusted Generic.__class_getitem__ argument unpacking.
vm/src/stdlib/typing.rs Re-exported set_typeparam_default from typevar module for public use.

Sequence Diagram(s)

sequenceDiagram
    participant Compiler
    participant VM
    participant Typing
    participant TypeParam

    Compiler->>VM: Emit instructions for type parameters
    alt Default value present
        Compiler->>VM: CallIntrinsic2(SetTypeparamDefault) with TypeParam, default
        VM->>Typing: set_typeparam_default(TypeParam, default)
        Typing-->>VM: Default set on TypeParam
    end
    Compiler->>VM: Emit class construction instructions
    alt TypeParams exist and no explicit bases
        Compiler->>VM: CallIntrinsic1(SubscriptGeneric) with type_params
        VM->>Typing: subscript_generic(type_params)
        Typing-->>VM: GenericAlias returned
        Compiler->>VM: Call __build_class__ with GenericAlias as base
    else Explicit bases present
        Compiler->>VM: Call __build_class__ with explicit bases
    else No type params
        Compiler->>VM: Call __build_class__ normally
    end
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Possibly related PRs

  • __type_params__ in __build_class__ #5883: Refactors type parameter handling in the compiler, including special symbol table management and class/function compilation logic, closely related to this PR's enhancements for PEP 695 support.

  • Fix TypeParams, TypeAlias compile #5862: Fixes compilation and execution of type parameters specifically for TypeAlias; related by modifying compile.rs but focusing on different constructs than this PR.

Suggested reviewers

  • arihant2math

Poem

In the warren where code bunnies dwell,
Type parameters now have defaults as well!
With intrinsic bytecode, they hop in line,
And classes generic—oh, how they shine!
A tuple of types, a carrot of base,
PEP 695’s magic fills the place.
🥕✨

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📥 Commits

Reviewing files that changed from the base of the PR and between f5d036e and bd54e53.

⛔ Files ignored due to path filters (2)
  • Lib/test/test_module/__init__.py is excluded by !Lib/**
  • Lib/test/test_typing.py is excluded by !Lib/**
📒 Files selected for processing (6)
  • compiler/codegen/src/compile.rs (2 hunks)
  • compiler/core/src/bytecode.rs (4 hunks)
  • vm/src/builtins/genericalias.rs (1 hunks)
  • vm/src/frame.rs (3 hunks)
  • vm/src/stdlib/typevar.rs (18 hunks)
  • vm/src/stdlib/typing.rs (1 hunks)
🚧 Files skipped from review as they are similar to previous changes (5)
  • vm/src/builtins/genericalias.rs
  • vm/src/stdlib/typing.rs
  • compiler/core/src/bytecode.rs
  • vm/src/frame.rs
  • compiler/codegen/src/compile.rs
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📓 Path-based instructions (1)
`**/*.rs`: Follow the default rustfmt code style (`cargo fmt` to format) Always ...

**/*.rs: Follow the default rustfmt code style (cargo fmt to format)
Always run clippy to lint code (cargo clippy) before completing tasks. Fix any warnings or lints that are introduced by your 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

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List of files the instruction was applied to:

  • vm/src/stdlib/typevar.rs
🧠 Learnings (1)
vm/src/stdlib/typevar.rs (1) 
Learnt from: CR
PR: RustPython/RustPython#0
File: .github/copilot-instructions.md:0-0
Timestamp: 2025-06-30T10:08:48.858Z
Learning: Applies to **/*.rs : Use the macro system (`pyclass`, `pymodule`, `pyfunction`, etc.) when implementing Python functionality in Rust
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🔇 Additional comments (5)
vm/src/stdlib/typevar.rs (5)

5-5: LGTM: Thread safety improvements for TypeVar.

The conversion of evaluate_default to PyMutex<PyObjectRef> aligns with the existing thread safety pattern used by other fields like bound and constraints. The access patterns are correctly updated to use .lock() throughout the implementation.

Also applies to: 80-80, 149-152, 176-176, 363-363, 389-390

404-405: LGTM: ParamSpec field type changes and thread safety.

The changes correctly handle the transition from Option<PyObjectRef> to PyObjectRef for default_value, using the NoDefault singleton pattern. The thread safety improvements with PyMutex are consistent with other type parameter implementations.

Also applies to: 466-478, 481-483, 491-497, 591-591, 597-597, 619-629

638-638: LGTM: TypeVarTuple thread safety improvements.

The thread safety changes for evaluate_default are consistent with the pattern used in TypeVar and ParamSpec implementations.

Also applies to: 654-657, 666-666, 758-758, 781-781

974-976: LGTM: Fixed CPython compatibility in Generic.class_getitem.

The change to delegate to the typing module's _generic_class_getitem function addresses the previous compatibility issue with tuple unwrapping. This approach ensures behavior matches CPython's implementation.

984-1022: LGTM: Well-implemented set_typeparam_default function.

The implementation is clean and follows good Rust practices:

  • Uses a generic helper function to reduce code duplication
  • Properly handles all three type parameter types (TypeVar, ParamSpec, TypeVarTuple)
  • Correctly uses mutex locks for thread safety
  • Appropriate error handling for invalid type parameters
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