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Implement cell comparison and repr
The cell type implemented neither Comparable nor Representable, so object's address-based defaults leaked through: cell(1) == cell(1) was False, ordering raised TypeError, and repr rendered <cell object at 0x...> rather than <cell at 0x...: int object at 0x...>. Compare cells by contents, with empty cells ordering before everything else, and render CPython's repr for both the filled and empty cases. Mark the type unhashable. Content-based equality combined with the inherited identity hash would break the hash/eq contract; CPython gets this implicitly, because defining tp_richcompare suppresses tp_hash inheritance. Reference: CPython Objects/cellobject.c, cell_richcompare and cell_repr. Assisted-by: Claude Code:claude-opus-5
1 parent 1c7759c commit bba2b7f

3 files changed

Lines changed: 33 additions & 4 deletions

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‎Lib/test/test_funcattrs.py‎

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@@ -432,7 +432,6 @@ def f():
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class CellTest(unittest.TestCase):
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@unittest.expectedFailure # TODO: RUSTPYTHON
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def test_comparison(self):
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# These tests are here simply to exercise the comparison code;
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# their presence should not be interpreted as providing any

‎Lib/test/test_reprlib.py‎

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@@ -237,7 +237,6 @@ def test_nesting(self):
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eq(r([[[[[[{}]]]]]]), "[[[[[[{}]]]]]]")
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eq(r([[[[[[[{}]]]]]]]), "[[[[[[[...]]]]]]]")
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@unittest.expectedFailure # TODO: RUSTPYTHON
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def test_cell(self):
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def get_cell():
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x = 42

‎crates/vm/src/builtins/function.rs‎

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@@ -1507,7 +1507,7 @@ impl Representable for PyBoundMethod {
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}
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}
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#[pyclass(module = false, name = "cell", traverse)]
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#[pyclass(module = false, name = "cell", unhashable = true, traverse)]
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#[derive(Debug, Default)]
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pub(crate) struct PyCell {
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contents: PyMutex<Option<PyObjectRef>>,
@@ -1530,7 +1530,7 @@ impl Constructor for PyCell {
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}
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}
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#[pyclass(with(Constructor))]
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#[pyclass(with(Constructor, Comparable, Representable))]
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impl PyCell {
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pub(crate) const fn new(contents: Option<PyObjectRef>) -> Self {
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Self {
@@ -1561,6 +1561,37 @@ impl PyCell {
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}
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}
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impl Comparable for PyCell {
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fn cmp(
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zelf: &Py<Self>,
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other: &PyObject,
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op: PyComparisonOp,
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vm: &VirtualMachine,
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) -> PyResult<PyComparisonValue> {
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let other = class_or_notimplemented!(Self, other);
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// compare cells by contents; empty cells come before anything else
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match (zelf.get(), other.get()) {
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(Some(a), Some(b)) => a.rich_compare(b, op, vm)?.is_true(vm).map(Into::into),
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(a, b) => Ok(op.eval_ord(b.is_none().cmp(&a.is_none())).into()),
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}
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}
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}
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impl Representable for PyCell {
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#[inline]
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fn repr_str(zelf: &Py<Self>, _vm: &VirtualMachine) -> PyResult<String> {
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let id = zelf.get_id();
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Ok(match zelf.get() {
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Some(value) => format!(
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"<cell at {id:#x}: {} object at {:#x}>",
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value.class().slot_name(),
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value.get_id()
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),
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None => format!("<cell at {id:#x}: empty>"),
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})
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}
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}
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/// Vectorcall implementation for PyFunction (PEP 590).
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/// Takes owned args to avoid cloning when filling fastlocals.
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pub(crate) fn vectorcall_function(

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