Fix set in-place operators with self argument (RustPython#6661)

HueCodes · terryluan12 · commit 4f66dec045a4 · 2026-01-14T19:15:41.000-05:00
Co-authored-by: Hugh &lt;HueCodes@users.noreply.github.com&gt;
diff --git a/crates/vm/src/builtins/set.rs b/crates/vm/src/builtins/set.rs
@@ -24,6 +24,7 @@ use crate::{
     vm::VirtualMachine,
 };
 use alloc::fmt;
+use core::borrow::Borrow;
 use core::ops::Deref;
 use rustpython_common::{
     atomic::{Ordering, PyAtomic, Radium},
@@ -719,8 +720,10 @@ impl PySet {
     }
 
     fn __iand__(zelf: PyRef<Self>, set: AnySet, vm: &VirtualMachine) -> PyResult<PyRef<Self>> {
-        zelf.inner
-            .intersection_update(core::iter::once(set.into_iterable(vm)?), vm)?;
+        if !set.is(zelf.as_object()) {
+            zelf.inner
+                .intersection_update(core::iter::once(set.into_iterable(vm)?), vm)?;
+        }
         Ok(zelf)
     }
 
@@ -731,8 +734,12 @@ impl PySet {
     }
 
     fn __isub__(zelf: PyRef<Self>, set: AnySet, vm: &VirtualMachine) -> PyResult<PyRef<Self>> {
-        zelf.inner
-            .difference_update(set.into_iterable_iter(vm)?, vm)?;
+        if set.is(zelf.as_object()) {
+            zelf.inner.clear();
+        } else {
+            zelf.inner
+                .difference_update(set.into_iterable_iter(vm)?, vm)?;
+        }
         Ok(zelf)
     }
 
@@ -748,8 +755,12 @@ impl PySet {
     }
 
     fn __ixor__(zelf: PyRef<Self>, set: AnySet, vm: &VirtualMachine) -> PyResult<PyRef<Self>> {
-        zelf.inner
-            .symmetric_difference_update(set.into_iterable_iter(vm)?, vm)?;
+        if set.is(zelf.as_object()) {
+            zelf.inner.clear();
+        } else {
+            zelf.inner
+                .symmetric_difference_update(set.into_iterable_iter(vm)?, vm)?;
+        }
         Ok(zelf)
     }
 
@@ -1297,6 +1308,13 @@ struct AnySet {
     object: PyObjectRef,
 }
 
+impl Borrow<PyObject> for AnySet {
+    #[inline(always)]
+    fn borrow(&self) -> &PyObject {
+        &self.object
+    }
+}
+
 impl AnySet {
     /// Check if object is a set or frozenset (including subclasses)
     /// Equivalent to CPython's PyAnySet_Check
diff --git a/extra_tests/snippets/builtin_set.py b/extra_tests/snippets/builtin_set.py
@@ -200,6 +200,18 @@ class S(set):
 with assert_raises(TypeError):
     a &= [1, 2, 3]
 
+a = set([1, 2, 3])
+a &= a
+assert a == set([1, 2, 3])
+
+a = set([1, 2, 3])
+a -= a
+assert a == set()
+
+a = set([1, 2, 3])
+a ^= a
+assert a == set()
+
 a = set([1, 2, 3])
 a.difference_update([3, 4, 5])
 assert a == set([1, 2])
