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Merged
youknowone merged 5 commits into from
Jun 29, 2025
Merged

Rework issubclass #5867

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8abf2da
check_exact
youknowone Jun 28, 2025
7a92989
check_class
youknowone Jun 28, 2025
241a8f1
Type compatibility tools
youknowone Jun 28, 2025
6e08225
abstract_issubclass
youknowone Jun 29, 2025
4e5007a
recursive_issubclass
youknowone Jun 29, 2025
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abstract_issubclass
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@youknowone
youknowone committed Jun 29, 2025
commit 6e0822570352597cbf955eaf916c71f824a4aba0
69 changes: 42 additions & 27 deletions vm/src/protocol/object.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -410,40 +410,55 @@ impl PyObject {
}

fn abstract_issubclass(&self, cls: &PyObject, vm: &VirtualMachine) -> PyResult<bool> {
let mut derived = self;
let mut first_item: PyObjectRef;
loop {
if derived.is(cls) {
return Ok(true);
}

let bases = derived.get_attr(identifier!(vm, __bases__), vm)?;
let tuple = PyTupleRef::try_from_object(vm, bases)?;
// # Safety: The lifetime of `derived` is forced to be ignored
let bases = unsafe {
let mut derived = self;
// First loop: handle single inheritance without recursion
loop {
if derived.is(cls) {
return Ok(true);
}

let n = tuple.len();
match n {
0 => {
let Some(bases) = derived.abstract_get_bases(vm)? else {
return Ok(false);
}
1 => {
first_item = tuple[0].clone();
derived = &first_item;
continue;
}
_ => {
for i in 0..n {
let check = vm.with_recursion("in abstract_issubclass", || {
tuple[i].abstract_issubclass(cls, vm)
})?;
if check {
return Ok(true);
}
};
let n = bases.len();
match n {
0 => return Ok(false),
1 => {
// Avoid recursion in the single inheritance case
// # safety
// Intention:
// ```
// derived = bases.as_slice()[0].as_object();
// ```
// Though type-system cannot guarantee, derived does live long enough in the loop.
derived = &*(bases.as_slice()[0].as_object() as *const _);
continue;
}
_ => {
// Multiple inheritance - break out to handle recursively
break bases;
}
}
}
};

return Ok(false);
// Second loop: handle multiple inheritance with recursion
// At this point we know n >= 2
let n = bases.len();
debug_assert!(n >= 2);

for i in 0..n {
let result = vm.with_recursion("in __issubclass__", || {
bases.as_slice()[i].abstract_issubclass(cls, vm)
})?;
if result {
return Ok(true);
}
}

Ok(false)
}

fn recursive_issubclass(&self, cls: &PyObject, vm: &VirtualMachine) -> PyResult<bool> {
Expand Down