PyTypeFlags::{SEQUENCE,MAPPING} by youknowone · Pull Request #6109 · RustPython/RustPython

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Walkthrough

Adds SEQUENCE and MAPPING type flags, applies them to builtin classes, and updates type creation to inherit/compute these flags (including via abc_tpflags). Also adds memoryview.class_getitem to support subscription-based generic aliasing. No runtime behavior changes beyond flag metadata and new classmethod.

Changes

Cohort / File(s)	Summary
Type flags definition `vm/src/types/slot.rs`	Adds `PyTypeFlags::SEQUENCE` and `PyTypeFlags::MAPPING` bitflags.
Builtin type flag updates `vm/src/builtins/dict.rs`, `vm/src/builtins/list.rs`, `vm/src/builtins/tuple.rs`, `vm/src/builtins/range.rs`, `vm/src/builtins/memory.rs`	Updates `#[pyclass]` flags: dict gains `MAPPING`; list/tuple/range/memoryview gain `SEQUENCE`.
Type creation flag propagation `vm/src/builtins/type.rs`	On type creation, inherits SEQUENCE/MAPPING from base types and reads `__abc_tpflags__` to set flags; integrates helpers into `new_heap_inner` and `new_static`.
MemoryView generic aliasing `vm/src/builtins/memory.rs`	Adds `__class_getitem__(cls, args, vm) -> PyGenericAlias` delegating to `PyGenericAlias::from_args`.

Sequence Diagram(s)

sequenceDiagram
  autonumber
  actor Dev as Developer
  participant VM as VM Type Creation
  participant Base as Base Type
  participant Helpers as Helpers
  note over VM,Helpers: New type initialization

  Dev->>VM: create type (heap/static)
  VM->>Base: read existing flags
  VM->>Helpers: inherit_patma_flags(SEQUENCE, MAPPING)
  Helpers-->>VM: apply missing flags from base
  VM->>Helpers: check_abc_tpflags(mro)
  Helpers-->>VM: parse int bits, set flags (non-overriding)
  VM-->>Dev: new type with updated PyTypeFlags

sequenceDiagram
  autonumber
  actor User as User Code
  participant Type as memoryview (type)
  participant VM as VM
  participant GA as PyGenericAlias

  User->>Type: memoryview[...]
  Type->>Type: __class_getitem__(cls, args, vm)
  Type->>GA: PyGenericAlias::from_args(cls, args, vm)
  GA-->>Type: generic alias
  Type-->>User: return alias

Estimated code review effort

🎯 3 (Moderate) | ⏱️ ~30 minutes

Possibly related PRs

feat(vm/slot): implement Py_TPFLAGS_MANAGED_DICT for class objects #5949 — Also modifies PyTypeFlags and type initialization logic; overlaps with flag handling paths.
Deprecate ::new_ref #6046 — Touches builtin types in vm/src/builtins/*; related to updates of pyclass metadata.
__class_getitem__ #5888 — Adds __class_getitem__ for memoryview; direct overlap with the new classmethod.

Poem

A rabbit taps flags with gentle delight,
SEQUENCE hops in, MAPPING holds tight.
Types learn from bases, like carrots from rows,
abc_tpflags whispers which way the wind blows.
memoryview[T] twinkles—alias in sight—
Code burrows deeper, and all feels right. 🥕

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