python · brandtbucher · Mar 17, 2022 · Mar 17, 2022 · Mar 17, 2022 · Mar 17, 2022
diff --git a/Doc/library/dis.rst b/Doc/library/dis.rst
@@ -1313,13 +1313,23 @@ iterations of the loop.
     .. versionadded:: 3.11
 
 
-.. opcode:: SEND
+.. opcode:: SEND (delta)
 
-    Sends ``None`` to the sub-generator of this generator.
-    Used in ``yield from`` and ``await`` statements.
+    Equivalent to ``TOS = TOS1.send(TOS)``. Used in ``yield from`` and ``await``
+    statements.
+
+    If the call raises :exc:`StopIteration`, pop both values, push its return
+    value, and increment the bytecode counter by *delta*.
+
+    If TOS1 is ``NULL`` (set when a ``throw()`` through the current frame
+    returns), pop both values, push TOS (its return value) back, and increment
+    the bytecode counter by *delta*.
 
     .. versionadded:: 3.11
 
+    .. versionchanged:: 3.12
+       Added ``NULL`` handling for subiterators that return during ``throw()``.
+
 
 .. opcode:: ASYNC_GEN_WRAP
 

diff --git a/Misc/NEWS.d/next/Core and Builtins/2022-03-17-11-40-20.bpo-46841.cU7e6B.rst b/Misc/NEWS.d/next/Core and Builtins/2022-03-17-11-40-20.bpo-46841.cU7e6B.rst
@@ -0,0 +1,3 @@
+When a sub-iterator returns a value during a ``throw()`` call, perform the
+resulting jump during the next :opcode:`SEND` instruction (rather than as
+part of the ``throw()`` implementation).
@@ -491,14 +491,8 @@ _gen_throw(PyGenObject *gen, int close_on_genexit,
             ret = _PyFrame_StackPop((_PyInterpreterFrame *)gen->gi_iframe);
             assert(ret == yf);
             Py_DECREF(ret);
-            // XXX: Performing this jump ourselves is awkward and problematic.
-            // See https://github.com/python/cpython/pull/31968.
-            /* Termination repetition of SEND loop */
-            assert(_PyInterpreterFrame_LASTI(frame) >= 0);
-            /* Backup to SEND */
-            assert(_Py_OPCODE(frame->prev_instr[-1]) == SEND);
-            int jump = _Py_OPARG(frame->prev_instr[-1]);
-            frame->prev_instr += jump - 1;
+            // NULL tells SEND to quit sending:
+            _PyFrame_StackPush((_PyInterpreterFrame *)gen->gi_iframe, NULL);
             if (_PyGen_FetchStopIterationValue(&val) == 0) {
                 ret = gen_send(gen, val);
                 Py_DECREF(val);

@@ -2591,6 +2591,12 @@ _PyEval_EvalFrameDefault(PyThreadState *tstate, _PyInterpreterFrame *frame, int
             assert(STACK_LEVEL() >= 2);
             PyObject *v = POP();
             PyObject *receiver = TOP();
+            if (receiver == NULL) {
+                // Receiver returned during a throw(). v is its return value:
+                SET_TOP(v);
+                JUMPBY(oparg);
+                DISPATCH();
+            }
             PySendResult gen_status;
             PyObject *retval;
             if (tstate->c_tracefunc == NULL) {