From 9ddd07a65620660d75d521ae019d0fa49d67ed4e Mon Sep 17 00:00:00 2001
From: Lee Dogeon <dev.moreal@gmail.com>
Date: Sun, 15 Mar 2026 17:04:23 +0900
Subject: [PATCH] Preserve imaginary zero signs when adding real values to
 complex numbers (#7421)

* Preserve imaginary zero signs when adding real values to complex numbers

* Refactor complex_add with match expression

* Correct complex real subtract op

* Remove unnecessary vm arugment
---
 Lib/test/test_builtin.py          |  1 -
 crates/vm/src/builtins/complex.rs | 60 +++++++++++++++++++++++++++++--
 2 files changed, 58 insertions(+), 3 deletions(-)

diff --git a/Lib/test/test_builtin.py b/Lib/test/test_builtin.py
index ff6175723..cf0268c2c 100644
--- a/Lib/test/test_builtin.py
+++ b/Lib/test/test_builtin.py
@@ -1971,7 +1971,6 @@ class BuiltinTest(ComplexesAreIdenticalMixin, unittest.TestCase):
 
     # test_str(): see test_str.py and test_bytes.py for str() tests.
 
-    @unittest.expectedFailure # TODO: RUSTPYTHON; AssertionError: floats 0.0 and -0.0 are not identical: zeros have different signs
     def test_sum(self):
         self.assertEqual(sum([]), 0)
         self.assertEqual(sum(list(range(2,8))), 27)
diff --git a/crates/vm/src/builtins/complex.rs b/crates/vm/src/builtins/complex.rs
index b3425d2aa..3e905b6ec 100644
--- a/crates/vm/src/builtins/complex.rs
+++ b/crates/vm/src/builtins/complex.rs
@@ -287,6 +287,44 @@ impl PyComplex {
             Ok(vm.ctx.not_implemented())
         }
     }
+
+    fn complex_real_binop<CCF, RCF, CRF, R>(
+        a: &PyObject,
+        b: &PyObject,
+        cc_op: CCF,
+        cr_op: CRF,
+        rc_op: RCF,
+        vm: &VirtualMachine,
+    ) -> PyResult
+    where
+        CCF: FnOnce(Complex64, Complex64) -> R,
+        CRF: FnOnce(Complex64, f64) -> R,
+        RCF: FnOnce(f64, Complex64) -> R,
+        R: ToPyResult,
+    {
+        let value = match (a.downcast_ref::<PyComplex>(), b.downcast_ref::<PyComplex>()) {
+            // complex + complex
+            (Some(a_complex), Some(b_complex)) => cc_op(a_complex.value, b_complex.value),
+            (Some(a_complex), None) => {
+                let Some(b_real) = float::to_op_float(b, vm)? else {
+                    return Ok(vm.ctx.not_implemented());
+                };
+
+                // complex + real
+                cr_op(a_complex.value, b_real)
+            }
+            (None, Some(b_complex)) => {
+                let Some(a_real) = float::to_op_float(a, vm)? else {
+                    return Ok(vm.ctx.not_implemented());
+                };
+
+                // real + complex
+                rc_op(a_real, b_complex.value)
+            }
+            (None, None) => return Ok(vm.ctx.not_implemented()),
+        };
+        value.to_pyresult(vm)
+    }
 }
 
 #[pyclass(
@@ -396,8 +434,26 @@ impl Hashable for PyComplex {
 impl AsNumber for PyComplex {
     fn as_number() -> &'static PyNumberMethods {
         static AS_NUMBER: PyNumberMethods = PyNumberMethods {
-            add: Some(|a, b, vm| PyComplex::number_op(a, b, |a, b, _vm| a + b, vm)),
-            subtract: Some(|a, b, vm| PyComplex::number_op(a, b, |a, b, _vm| a - b, vm)),
+            add: Some(|a, b, vm| {
+                PyComplex::complex_real_binop(
+                    a,
+                    b,
+                    |a, b| a + b,
+                    |a_complex, b_real| Complex64::new(a_complex.re + b_real, a_complex.im),
+                    |a_real, b_complex| Complex64::new(a_real + b_complex.re, b_complex.im),
+                    vm,
+                )
+            }),
+            subtract: Some(|a, b, vm| {
+                PyComplex::complex_real_binop(
+                    a,
+                    b,
+                    |a, b| a - b,
+                    |a_complex, b_real| Complex64::new(a_complex.re - b_real, a_complex.im),
+                    |a_real, b_complex| Complex64::new(a_real - b_complex.re, -b_complex.im),
+                    vm,
+                )
+            }),
             multiply: Some(|a, b, vm| PyComplex::number_op(a, b, |a, b, _vm| a * b, vm)),
             power: Some(|a, b, c, vm| {
                 if vm.is_none(c) {