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Merged
youknowone merged 6 commits into from
Dec 26, 2025
Merged

Prevent __class__ reassignment across incompatible layouts #6521

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3271b74
Initial plan
Copilot Dec 25, 2025
a3fb6fe
fix: guard __class__ reassignment layout
Copilot Dec 25, 2025
fbdb400
Auto-format: cargo fmt --all
github-actions[bot] Dec 25, 2025
71e9eb7
test: move __class__ layout check to builtin_type snippet
Copilot Dec 25, 2025
89e0801
fix: allow module __class__ reassignment with matching layout
Copilot Dec 25, 2025
e0090ff
Fix condition
youknowone Dec 26, 2025
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test: move __class__ layout check to builtin_type snippet 
Co-authored-by: youknowone <69878+youknowone@users.noreply.github.com>
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@youknowone
Copilot and youknowone committed Dec 26, 2025
commit 71e9eb7431741c9862ad16b302e4a1e84d5ea0bb
27 changes: 0 additions & 27 deletions crates/vm/src/vm/interpreter.rs
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@youknowone youknowone Dec 25, 2025

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Instead of adding test in rust code, add test test in builtin_type.py

Original file line number Diff line number Diff line change
Expand Up @@ -169,31 +169,4 @@ mod tests {
assert_eq!(value.as_str(), "Hello Hello Hello Hello ")
})
}

#[test]
fn class_assignment_layout_mismatch_error() {
Interpreter::without_stdlib(Default::default()).enter(|vm| {
let scope = vm.new_scope_with_builtins();
let source = r#"
class TypeA:
def __init__(self):
self.a = 1

class TypeB:
__slots__ = "b"
def __init__(self):
self.b = 2

obj = TypeA()
try:
obj.__class__ = TypeB
except TypeError as e:
assert str(e) == "__class__ assignment: 'TypeB' object layout differs from 'TypeA'"
else:
raise AssertionError("TypeError not raised")
"#;
vm.run_code_string(scope, source, "<test>".to_owned())
.expect("script should complete without uncaught exceptions");
})
}
}
20 changes: 20 additions & 0 deletions extra_tests/snippets/builtin_type.py
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Original file line number Diff line number Diff line change
Expand Up @@ -240,6 +240,26 @@ class C(B, BB):
assert C.mro() == [C, B, A, BB, AA, object]


class TypeA:
def __init__(self):
self.a = 1


class TypeB:
__slots__ = "b"

def __init__(self):
self.b = 2


obj = TypeA()
with assert_raises(TypeError) as cm:
obj.__class__ = TypeB
assert "__class__ assignment: 'TypeB' object layout differs from 'TypeA'" in str(
cm.exception
)


assert type(Exception.args).__name__ == "getset_descriptor"
assert type(None).__bool__(None) is False

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