Borrow exception and dict methods that only read self (#8808)

add_note, __reduce__, and __setstate__ take &Py<BaseException>.
dict.__ror__ takes &Py<PyDict>. Callers drop the clone made for add_note.

Assisted-by: Grok CLI:grok-4.7

crates/stdlib/src/json.rs

@@ -881,7 +881,7 @@ mod _json {
     fn add_note(exc: PyBaseExceptionRef, note: Wtf8Buf, vm: &VirtualMachine) -> PyBaseExceptionRef {
         // `PyBaseException::add_note` is `pub`, so call it directly instead
         // of going through the generic attribute-lookup + call machinery.
-        let _ = exc.clone().add_note(vm.ctx.new_str(note), vm);
+        let _ = exc.add_note(vm.ctx.new_str(note), vm);
         exc
     }
 

crates/stdlib/src/pickle.rs

@@ -2133,7 +2133,7 @@ mod _pickle {
     // saving
 
     fn add_note(err: PyBaseExceptionRef, note: String, vm: &VirtualMachine) -> PyBaseExceptionRef {
-        let _ = err.clone().add_note(vm.ctx.new_str(note), vm);
+        let _ = err.add_note(vm.ctx.new_str(note), vm);
         err
     }
 

crates/vm/src/builtins/dict.rs

@@ -585,6 +585,16 @@ impl Py<PyDict> {
     fn __getitem__(&self, key: PyObjectRef, vm: &VirtualMachine) -> PyResult {
         self.inner_getitem(&*key, vm)
     }
+
+    fn __ror__(&self, other: PyObjectRef, vm: &VirtualMachine) -> PyResult {
+        let other_dict = other.downcast::<PyDict>();
+        if let Ok(other) = other_dict {
+            let other_cp = other.copy();
+            other_cp.merge_dict(self, true, vm)?;
+            return Ok(other_cp.into_pyobject(vm));
+        }
+        Ok(vm.ctx.not_implemented())
+    }
 }
 
 #[pyclass]
@@ -613,16 +623,6 @@ impl PyRef<PyDict> {
         self.merge_object(other, vm)?;
         Ok(self)
     }
-
-    fn __ror__(self, other: PyObjectRef, vm: &VirtualMachine) -> PyResult {
-        let other_dict: Result<Self, _> = other.downcast();
-        if let Ok(other) = other_dict {
-            let other_cp = other.copy();
-            other_cp.merge_dict(&self, true, vm)?;
-            return Ok(other_cp.into_pyobject(vm));
-        }
-        Ok(vm.ctx.not_implemented())
-    }
 }
 
 impl DefaultConstructor for PyDict {}

crates/vm/src/exceptions.rs

@@ -786,18 +786,9 @@ impl Py<PyBaseException> {
             Err(i) => PyStr::from(format!("({})", i.format(", "))).into_ref(&vm.ctx),
         }
     }
-}
-
-#[pyclass]
-impl PyRef<PyBaseException> {
-    #[pymethod]
-    fn with_traceback(self, tb: Option<PyTracebackRef>) -> Self {
-        *self.traceback.write() = tb;
-        self
-    }
 
     #[pymethod]
-    pub fn add_note(self, note: PyStrRef, vm: &VirtualMachine) -> PyResult<()> {
+    pub fn add_note(&self, note: PyStrRef, vm: &VirtualMachine) -> PyResult<()> {
         let dict = crate::builtins::object::object_get_dict(self.as_object().to_owned(), vm)
             .map_err(|_| vm.new_attribute_error("Exception object has no __dict__"))?;
 
@@ -818,7 +809,7 @@ impl PyRef<PyBaseException> {
     }
 
     #[pymethod]
-    fn __reduce__(self, vm: &VirtualMachine) -> PyTupleRef {
+    fn __reduce__(&self, vm: &VirtualMachine) -> PyTupleRef {
         if let Some(dict) = self.as_object().dict().filter(|x| !x.is_empty()) {
             vm.new_tuple((self.class().to_owned(), self.args(), dict))
         } else {
@@ -827,7 +818,7 @@ impl PyRef<PyBaseException> {
     }
 
     #[pymethod]
-    fn __setstate__(self, state: PyObjectRef, vm: &VirtualMachine) -> PyResult<PyObjectRef> {
+    fn __setstate__(&self, state: PyObjectRef, vm: &VirtualMachine) -> PyResult<PyObjectRef> {
         if !vm.is_none(&state) {
             let dict = state
                 .downcast::<crate::builtins::PyDict>()
@@ -845,6 +836,15 @@ impl PyRef<PyBaseException> {
     }
 }
 
+#[pyclass]
+impl PyRef<PyBaseException> {
+    #[pymethod]
+    fn with_traceback(self, tb: Option<PyTracebackRef>) -> Self {
+        *self.traceback.write() = tb;
+        self
+    }
+}
+
 impl Constructor for PyBaseException {
     type Args = FuncArgs;