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

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Merged
youknowone merged 1 commit into from
Aug 26, 2025
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PyTypeFlags::{SEQUENCE,MAPPING} #6109

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PyTypeFlags::{SEQUENCE,MAPPING}
  • Loading branch information
@youknowone
youknowone committed Aug 25, 2025
commit 96364acbdf60b841b0f65df011bc42449b6b0b5d
2 changes: 1 addition & 1 deletion vm/src/builtins/dict.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -176,7 +176,7 @@ impl PyDict {
AsMapping,
Representable
),
flags(BASETYPE)
flags(BASETYPE, MAPPING)
)]
impl PyDict {
#[pyclassmethod]
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2 changes: 1 addition & 1 deletion vm/src/builtins/list.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -109,7 +109,7 @@ pub type PyListRef = PyRef<PyList>;
AsSequence,
Representable
),
flags(BASETYPE)
flags(BASETYPE, SEQUENCE)
)]
impl PyList {
#[pymethod]
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25 changes: 14 additions & 11 deletions vm/src/builtins/memory.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -538,17 +538,20 @@ impl Py<PyMemoryView> {
}
}

#[pyclass(with(
Py,
Hashable,
Comparable,
AsBuffer,
AsMapping,
AsSequence,
Constructor,
Iterable,
Representable
))]
#[pyclass(
with(
Py,
Hashable,
Comparable,
AsBuffer,
AsMapping,
AsSequence,
Constructor,
Iterable,
Representable
),
flags(SEQUENCE)
)]
impl PyMemoryView {
// TODO: Uncomment when Python adds __class_getitem__ to memoryview
// #[pyclassmethod]
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21 changes: 12 additions & 9 deletions vm/src/builtins/range.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -174,15 +174,18 @@ pub fn init(context: &Context) {
PyRangeIterator::extend_class(context, context.types.range_iterator_type);
}

#[pyclass(with(
Py,
AsMapping,
AsSequence,
Hashable,
Comparable,
Iterable,
Representable
))]
#[pyclass(
with(
Py,
AsMapping,
AsSequence,
Hashable,
Comparable,
Iterable,
Representable
),
flags(SEQUENCE)
)]
impl PyRange {
fn new(cls: PyTypeRef, stop: ArgIndex, vm: &VirtualMachine) -> PyResult<PyRef<Self>> {
Self {
Expand Down
2 changes: 1 addition & 1 deletion vm/src/builtins/tuple.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -244,7 +244,7 @@ impl<T> PyTuple<PyRef<T>> {
}

#[pyclass(
flags(BASETYPE),
flags(BASETYPE, SEQUENCE),
with(
AsMapping,
AsSequence,
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64 changes: 64 additions & 0 deletions vm/src/builtins/type.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -31,6 +31,7 @@ use crate::{
};
use indexmap::{IndexMap, map::Entry};
use itertools::Itertools;
use num_traits::ToPrimitive;
use std::{borrow::Borrow, collections::HashSet, ops::Deref, pin::Pin, ptr::NonNull};

#[pyclass(module = false, name = "type", traverse = "manual")]
Expand Down Expand Up @@ -231,6 +232,58 @@ impl PyType {
linearise_mro(mros)
}

/// Inherit SEQUENCE and MAPPING flags from base class (CPython: inherit_patma_flags)
fn inherit_patma_flags(slots: &mut PyTypeSlots, base: &PyRef<Self>) {
const COLLECTION_FLAGS: PyTypeFlags = PyTypeFlags::from_bits_truncate(
PyTypeFlags::SEQUENCE.bits() | PyTypeFlags::MAPPING.bits(),
);
if !slots.flags.intersects(COLLECTION_FLAGS) {
slots.flags |= base.slots.flags & COLLECTION_FLAGS;
}
}

/// 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;
}
}
}
}

Comment on lines +245 to +286

@coderabbitai coderabbitai Bot Aug 25, 2025

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🛠️ 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

‼️ IMPORTANT
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.

Suggested change
/// 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.

#[allow(clippy::too_many_arguments)]
fn new_heap_inner(
base: PyRef<Self>,
Expand All @@ -246,6 +299,13 @@ impl PyType {
if base.slots.flags.has_feature(PyTypeFlags::HAS_DICT) {
slots.flags |= PyTypeFlags::HAS_DICT
}

// Inherit SEQUENCE and MAPPING flags from base class
Self::inherit_patma_flags(&mut slots, &base);

// Check for __abc_tpflags__ from ABCMeta (for collections.abc.Sequence, Mapping, etc.)
Self::check_abc_tpflags(&mut slots, &attrs, &bases, ctx);

if slots.basicsize == 0 {
slots.basicsize = base.slots.basicsize;
}
Expand Down Expand Up @@ -297,6 +357,10 @@ impl PyType {
if base.slots.flags.has_feature(PyTypeFlags::HAS_DICT) {
slots.flags |= PyTypeFlags::HAS_DICT
}

// Inherit SEQUENCE and MAPPING flags from base class
Self::inherit_patma_flags(&mut slots, &base);

if slots.basicsize == 0 {
slots.basicsize = base.slots.basicsize;
}
Expand Down
2 changes: 2 additions & 0 deletions vm/src/types/slot.rs
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Expand Up @@ -123,6 +123,8 @@ bitflags! {
#[non_exhaustive]
pub struct PyTypeFlags: u64 {
const MANAGED_DICT = 1 << 4;
const SEQUENCE = 1 << 5;
const MAPPING = 1 << 6;
const IMMUTABLETYPE = 1 << 8;
const HEAPTYPE = 1 << 9;
const BASETYPE = 1 << 10;
Expand Down