coroutines: Error when awaiting on coroutine that's being awaited
Issue #25888
diff --git a/Python/ceval.c b/Python/ceval.c
index aee0e6b..f9ecad4 100644
--- a/Python/ceval.c
+++ b/Python/ceval.c
@@ -2021,6 +2021,21 @@
Py_DECREF(iterable);
+ if (iter != NULL && PyCoro_CheckExact(iter)) {
+ PyObject *yf = _PyGen_yf((PyGenObject*)iter);
+ if (yf != NULL) {
+ /* `iter` is a coroutine object that is being
+ awaited, `yf` is a pointer to the current awaitable
+ being awaited on. */
+ Py_DECREF(yf);
+ Py_CLEAR(iter);
+ PyErr_SetString(
+ PyExc_RuntimeError,
+ "coroutine is being awaited already");
+ /* The code below jumps to `error` if `iter` is NULL. */
+ }
+ }
+
SET_TOP(iter); /* Even if it's NULL */
if (iter == NULL) {