PyTypeFlags::{SEQUENCE,MAPPING} #6109
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WalkthroughAdds 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
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
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Actionable comments posted: 1
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⚠️ Outside diff range comments (1)
vm/src/builtins/memory.rs (1)
558-560: Bug: class_getitem isn’t exposed without #[pyclassmethod]The method compiles but won’t be visible to Python without the macro attribute. The current comment suggests intent to expose it; please add #[pyclassmethod] so memoryview[...] works.
Apply:
- // TODO: Uncomment when Python adds __class_getitem__ to memoryview - // #[pyclassmethod] - fn __class_getitem__(cls: PyTypeRef, args: PyObjectRef, vm: &VirtualMachine) -> PyGenericAlias { + #[pyclassmethod] + fn __class_getitem__(cls: PyTypeRef, args: PyObjectRef, vm: &VirtualMachine) -> PyGenericAlias { PyGenericAlias::from_args(cls, args, vm) }Optionally, add a small test covering memoryview[int] creation.
I can draft a unit/integration test ensuring memoryview.class_getitem returns a PyGenericAlias and that memoryview[int].origin is memoryview.
🧹 Nitpick comments (1)
vm/src/builtins/type.rs (1)
235-244: Nit: simplify flag set constructionYou can construct COLLECTION_FLAGS directly with bitflags OR. It’s clearer and const-evaluable without from_bits_truncate.
- const COLLECTION_FLAGS: PyTypeFlags = PyTypeFlags::from_bits_truncate( - PyTypeFlags::SEQUENCE.bits() | PyTypeFlags::MAPPING.bits(), - ); + const COLLECTION_FLAGS: PyTypeFlags = PyTypeFlags::SEQUENCE | PyTypeFlags::MAPPING;
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📒 Files selected for processing (7)
vm/src/builtins/dict.rs(1 hunks)vm/src/builtins/list.rs(1 hunks)vm/src/builtins/memory.rs(1 hunks)vm/src/builtins/range.rs(1 hunks)vm/src/builtins/tuple.rs(1 hunks)vm/src/builtins/type.rs(4 hunks)vm/src/types/slot.rs(1 hunks)
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**/*.rs
📄 CodeRabbit inference engine (.github/copilot-instructions.md)
**/*.rs: Follow the default rustfmt code style (cargo fmtto 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
Files:
vm/src/builtins/list.rsvm/src/types/slot.rsvm/src/builtins/dict.rsvm/src/builtins/tuple.rsvm/src/builtins/range.rsvm/src/builtins/type.rsvm/src/builtins/memory.rs
🧬 Code graph analysis (1)
vm/src/builtins/range.rs (2)
derive/src/lib.rs (1)
pyclass(124-128)derive-impl/src/util.rs (1)
with(305-317)
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🔇 Additional comments (9)
vm/src/types/slot.rs (1)
126-127: Add documentation for SEQUENCE and MAPPING flagsThe new flags in
vm/src/types/slot.rsare correctly placed at bits1<<5and1<<6and already propagate as expected:
- SEQUENCE is applied to
list,tuple,range, andmemoryviewin
vm/src/builtins/{list,tuple,range,memory}.rs.- MAPPING is applied to
dictinvm/src/builtins/dict.rs.- Both flags are used in the ABC/type-creation logic (
inherit_patma_flagsand__abc_tpflags__) invm/src/builtins/type.rs.Please add these inline docs at the definition site:
--- a/vm/src/types/slot.rs +++ b/vm/src/types/slot.rs @@ lines 126-127 - const SEQUENCE = 1 << 5; - const MAPPING = 1 << 6; + /// Semantically sequence-like types (e.g., list, tuple, range, memoryview). + /// This is a nominal flag used by type/ABC logic, not a raw “has sq_* slots” check. + const SEQUENCE = 1 << 5; + /// Semantically mapping-like types (e.g., dict). + /// Nominal flag; presence of mp_* slots alone shouldn’t set this. + const MAPPING = 1 << 6;With these comments in place, the implementation and propagation checks are complete.
vm/src/builtins/list.rs (1)
112-113: Marking list with SEQUENCE is correct and consistent with its behavior.List also exposes mapping slots for index-based get/set, but not setting the MAPPING flag is appropriate; the nominal “mapping” concept shouldn’t apply to list.
vm/src/builtins/tuple.rs (1)
247-247: Tuple flagged as SEQUENCE — good alignment with protocol and slots.No further action; consistent with AsSequence implementation.
vm/src/builtins/dict.rs (1)
179-180: Dict flagged as MAPPING — matches semantics and ABC expectations.Dict keeps AsSequence for contains/len, but not marking SEQUENCE is correct.
vm/src/builtins/range.rs (1)
177-188: Range flagged as SEQUENCE — matches Python’s semantics.Length/getitem paths already go through protocol_length/downcasts appropriately; no issues spotted.
vm/src/builtins/type.rs (3)
303-308: LGTM: flag propagation order matches CPython intentInheriting from the best base and only consulting abc_tpflags if neither SEQUENCE nor MAPPING is set aligns with CPython’s “don’t override explicit/base-provided flags” behavior.
361-363: LGTM: static type creation also inherits collection flagsPropagating SEQUENCE/MAPPING for static types ensures builtin subclasses correctly advertise their pattern-matching traits.
34-34: No action needed:num-traitsis already declared and aligned
The workspace rootCargo.tomlpinsnum-traits = "0.2", and thevmcrate (along with all other workspace members) references it viaworkspace = true. Theuse num_traits::ToPrimitiveimport is satisfied—no further dependency changes are required.vm/src/builtins/memory.rs (1)
541-554: LGTM: advertise memoryview as a SEQUENCEGiven memoryview implements AsSequence (length, item) and is used as a sequence in pattern matching contexts, the flags(SEQUENCE) addition is appropriate. Keeping MAPPING out is correct despite AsMapping support, since memoryview is not semantically a mapping.
| /// Check for __abc_tpflags__ and set the appropriate flags | ||
| /// This checks in attrs and all base classes for __abc_tpflags__ | ||
| fn check_abc_tpflags( | ||
| slots: &mut PyTypeSlots, | ||
| attrs: &PyAttributes, | ||
| bases: &[PyRef<Self>], | ||
| ctx: &Context, | ||
| ) { | ||
| const COLLECTION_FLAGS: PyTypeFlags = PyTypeFlags::from_bits_truncate( | ||
| PyTypeFlags::SEQUENCE.bits() | PyTypeFlags::MAPPING.bits(), | ||
| ); | ||
|
|
||
| // Don't override if flags are already set | ||
| if slots.flags.intersects(COLLECTION_FLAGS) { | ||
| return; | ||
| } | ||
|
|
||
| // First check in our own attributes | ||
| let abc_tpflags_name = ctx.intern_str("__abc_tpflags__"); | ||
| if let Some(abc_tpflags_obj) = attrs.get(abc_tpflags_name) { | ||
| if let Some(int_obj) = abc_tpflags_obj.downcast_ref::<crate::builtins::int::PyInt>() { | ||
| let flags_val = int_obj.as_bigint().to_i64().unwrap_or(0); | ||
| let abc_flags = PyTypeFlags::from_bits_truncate(flags_val as u64); | ||
| slots.flags |= abc_flags & COLLECTION_FLAGS; | ||
| return; | ||
| } | ||
| } | ||
|
|
||
| // Then check in base classes | ||
| for base in bases { | ||
| if let Some(abc_tpflags_obj) = base.find_name_in_mro(abc_tpflags_name) { | ||
| if let Some(int_obj) = abc_tpflags_obj.downcast_ref::<crate::builtins::int::PyInt>() | ||
| { | ||
| let flags_val = int_obj.as_bigint().to_i64().unwrap_or(0); | ||
| let abc_flags = PyTypeFlags::from_bits_truncate(flags_val as u64); | ||
| slots.flags |= abc_flags & COLLECTION_FLAGS; | ||
| return; | ||
| } | ||
| } | ||
| } | ||
| } | ||
|
|
There was a problem hiding this comment.
🛠️ Refactor suggestion
Fix: avoid silently zeroing or truncating abc_tpflags when converting from PyInt
Using to_i64().unwrap_or(0) will:
- turn any large positive flag value (> i64::MAX) into 0,
- turn any negative value into 0,
- silently mask real issues.
At minimum, prefer an unsigned conversion and ignore non-convertible values; this avoids introducing incorrect zero flags. If you want CPython-compatible behavior (PyLong_AsUnsignedLongMask), you can additionally mask to the low 64 bits, but even the minimal fix below prevents accidental zeroing.
Apply this diff (both occurrences inside check_abc_tpflags):
- if let Some(int_obj) = abc_tpflags_obj.downcast_ref::<crate::builtins::int::PyInt>() {
- let flags_val = int_obj.as_bigint().to_i64().unwrap_or(0);
- let abc_flags = PyTypeFlags::from_bits_truncate(flags_val as u64);
- slots.flags |= abc_flags & COLLECTION_FLAGS;
- return;
- }
+ if let Some(int_obj) = abc_tpflags_obj.downcast_ref::<crate::builtins::int::PyInt>() {
+ if let Some(flags_val) = int_obj.as_bigint().to_u64() {
+ let abc_flags = PyTypeFlags::from_bits_truncate(flags_val);
+ slots.flags |= abc_flags & COLLECTION_FLAGS;
+ return;
+ }
+ }And:
- if let Some(int_obj) = abc_tpflags_obj.downcast_ref::<crate::builtins::int::PyInt>()
- {
- let flags_val = int_obj.as_bigint().to_i64().unwrap_or(0);
- let abc_flags = PyTypeFlags::from_bits_truncate(flags_val as u64);
- slots.flags |= abc_flags & COLLECTION_FLAGS;
- return;
- }
+ if let Some(int_obj) = abc_tpflags_obj.downcast_ref::<crate::builtins::int::PyInt>()
+ {
+ if let Some(flags_val) = int_obj.as_bigint().to_u64() {
+ let abc_flags = PyTypeFlags::from_bits_truncate(flags_val);
+ slots.flags |= abc_flags & COLLECTION_FLAGS;
+ return;
+ }
+ }If you’d like parity with PyLong_AsUnsignedLongMask, I can follow up with a small helper that extracts the low 64 bits (two’s complement) from BigInt.
📝 Committable suggestion
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Carefully review the code before committing. Ensure that it accurately replaces the highlighted code, contains no missing lines, and has no issues with indentation. Thoroughly test & benchmark the code to ensure it meets the requirements.
| /// Check for __abc_tpflags__ and set the appropriate flags | |
| /// This checks in attrs and all base classes for __abc_tpflags__ | |
| fn check_abc_tpflags( | |
| slots: &mut PyTypeSlots, | |
| attrs: &PyAttributes, | |
| bases: &[PyRef<Self>], | |
| ctx: &Context, | |
| ) { | |
| const COLLECTION_FLAGS: PyTypeFlags = PyTypeFlags::from_bits_truncate( | |
| PyTypeFlags::SEQUENCE.bits() | PyTypeFlags::MAPPING.bits(), | |
| ); | |
| // Don't override if flags are already set | |
| if slots.flags.intersects(COLLECTION_FLAGS) { | |
| return; | |
| } | |
| // First check in our own attributes | |
| let abc_tpflags_name = ctx.intern_str("__abc_tpflags__"); | |
| if let Some(abc_tpflags_obj) = attrs.get(abc_tpflags_name) { | |
| if let Some(int_obj) = abc_tpflags_obj.downcast_ref::<crate::builtins::int::PyInt>() { | |
| let flags_val = int_obj.as_bigint().to_i64().unwrap_or(0); | |
| let abc_flags = PyTypeFlags::from_bits_truncate(flags_val as u64); | |
| slots.flags |= abc_flags & COLLECTION_FLAGS; | |
| return; | |
| } | |
| } | |
| // Then check in base classes | |
| for base in bases { | |
| if let Some(abc_tpflags_obj) = base.find_name_in_mro(abc_tpflags_name) { | |
| if let Some(int_obj) = abc_tpflags_obj.downcast_ref::<crate::builtins::int::PyInt>() | |
| { | |
| let flags_val = int_obj.as_bigint().to_i64().unwrap_or(0); | |
| let abc_flags = PyTypeFlags::from_bits_truncate(flags_val as u64); | |
| slots.flags |= abc_flags & COLLECTION_FLAGS; | |
| return; | |
| } | |
| } | |
| } | |
| } | |
| /// Check for __abc_tpflags__ and set the appropriate flags | |
| /// This checks in attrs and all base classes for __abc_tpflags__ | |
| fn check_abc_tpflags( | |
| slots: &mut PyTypeSlots, | |
| attrs: &PyAttributes, | |
| bases: &[PyRef<Self>], | |
| ctx: &Context, | |
| ) { | |
| const COLLECTION_FLAGS: PyTypeFlags = PyTypeFlags::from_bits_truncate( | |
| PyTypeFlags::SEQUENCE.bits() | PyTypeFlags::MAPPING.bits(), | |
| ); | |
| // Don't override if flags are already set | |
| if slots.flags.intersects(COLLECTION_FLAGS) { | |
| return; | |
| } | |
| // First check in our own attributes | |
| let abc_tpflags_name = ctx.intern_str("__abc_tpflags__"); | |
| if let Some(abc_tpflags_obj) = attrs.get(abc_tpflags_name) { | |
| if let Some(int_obj) = abc_tpflags_obj.downcast_ref::<crate::builtins::int::PyInt>() { | |
| if let Some(flags_val) = int_obj.as_bigint().to_u64() { | |
| let abc_flags = PyTypeFlags::from_bits_truncate(flags_val); | |
| slots.flags |= abc_flags & COLLECTION_FLAGS; | |
| return; | |
| } | |
| } | |
| } | |
| // Then check in base classes | |
| for base in bases { | |
| if let Some(abc_tpflags_obj) = base.find_name_in_mro(abc_tpflags_name) { | |
| if let Some(int_obj) = abc_tpflags_obj.downcast_ref::<crate::builtins::int::PyInt>() { | |
| if let Some(flags_val) = int_obj.as_bigint().to_u64() { | |
| let abc_flags = PyTypeFlags::from_bits_truncate(flags_val); | |
| slots.flags |= abc_flags & COLLECTION_FLAGS; | |
| return; | |
| } | |
| } | |
| } | |
| } | |
| } |
🤖 Prompt for AI Agents
In vm/src/builtins/type.rs around lines 245–286, the code uses
to_i64().unwrap_or(0) when reading __abc_tpflags__, which can silently turn
large/negative BigInt values into 0; replace that conversion with an
unsigned-aware approach: call the BigInt -> u64 conversion (e.g.
ToPrimitive::to_u64 or an equivalent helper) and if it returns None, treat the
value as non-convertible and skip applying flags (do not default to 0); if you
need CPython parity instead, extract the low 64 bits (unsigned mask) from the
BigInt (two’s complement) and use that u64. Apply this change in both places
inside check_abc_tpflags so flags are not silently zeroed or truncated.
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