Initial proof-of-concept for yielding synchronous functions.

Author: ZeroIntensity

Include/internal/pycore_genobject.h

@@ -32,10 +32,12 @@ PyAPI_FUNC(int) _PyGen_FetchStopIterationValue(PyObject **);
 
 PyAPI_FUNC(PyObject *)_PyCoro_GetAwaitableIter(PyObject *o);
 PyAPI_FUNC(PyObject *)_PyAsyncGenValueWrapperNew(PyThreadState *state, PyObject *);
+PyAPI_FUNC(PyObject *)_PyAsyncGenYieldFrom_New(PyThreadState *state, PyObject *);
 
 extern PyTypeObject _PyCoroWrapper_Type;
 extern PyTypeObject _PyAsyncGenWrappedValue_Type;
 extern PyTypeObject _PyAsyncGenAThrow_Type;
+extern PyTypeObject _PyAsyncGenYieldFrom_Type;
 
 #ifdef __cplusplus
 }

Include/internal/pycore_intrinsics.h

@@ -18,8 +18,9 @@
 #define INTRINSIC_TYPEVARTUPLE                   9
 #define INTRINSIC_SUBSCRIPT_GENERIC             10
 #define INTRINSIC_TYPEALIAS                     11
+#define INSTRINSIC_ASYNC_GEN_WRAP_YIELD_FROM    12
 
-#define MAX_INTRINSIC_1                         11
+#define MAX_INTRINSIC_1                         12
 
 
 /* Binary Functions: */

Objects/genobject.c

@@ -2605,3 +2605,111 @@ async_gen_athrow_new(PyAsyncGenObject *gen, PyObject *args)
     _PyObject_GC_TRACK((PyObject*)o);
     return (PyObject*)o;
 }
+
+typedef struct {
+    PyObject_HEAD
+    PyObject *agyf_iterator;
+} _PyAsyncGenYieldFrom;
+
+#define _PyAsyncGenYieldFrom_CAST(op) ((_PyAsyncGenYieldFrom *)op)
+
+static int
+async_gen_yield_from_traverse(PyObject *op, visitproc visit, void *arg)
+{
+    assert(op != NULL);
+    _PyAsyncGenYieldFrom *self = _PyAsyncGenYieldFrom_CAST(op);
+    Py_VISIT(self->agyf_iterator);
+    return 0;
+}
+
+static int
+async_gen_yield_from_clear(PyObject *op)
+{
+    assert(op != NULL);
+    _PyAsyncGenYieldFrom *self = _PyAsyncGenYieldFrom_CAST(op);
+    Py_CLEAR(self->agyf_iterator);
+    return 0;
+}
+
+static void
+async_gen_yield_from_dealloc(PyObject *op)
+{
+    assert(op != NULL);
+    _PyAsyncGenYieldFrom *self = _PyAsyncGenYieldFrom_CAST(op);
+    _PyObject_GC_UNTRACK(op);
+    (void)async_gen_yield_from_clear(op);
+    PyObject_GC_Del(op);
+}
+
+static PyObject *
+async_gen_yield_from_iternext(PyObject *op)
+{
+    assert(op != NULL);
+    _PyAsyncGenYieldFrom *self = _PyAsyncGenYieldFrom_CAST(op);
+    PyObject *result = PyIter_Next(self->agyf_iterator);
+    if (result == NULL) {
+        return NULL;
+    }
+
+    PyObject *wrapped = _PyAsyncGenValueWrapperNew(_PyThreadState_GET(), result);
+    Py_DECREF(result);
+    return wrapped;
+}
+
+PyTypeObject _PyAsyncGenYieldFrom_Type = {
+    PyVarObject_HEAD_INIT(&PyType_Type, 0)
+    "async_generator_yield_from",               /* tp_name */
+    sizeof(_PyAsyncGenYieldFrom),               /* tp_basicsize */
+    0,                                          /* tp_itemsize */
+    /* methods */
+    async_gen_yield_from_dealloc,               /* tp_dealloc */
+    0,                                          /* tp_vectorcall_offset */
+    0,                                          /* tp_getattr */
+    0,                                          /* tp_setattr */
+    0,                                          /* tp_as_async */
+    0,                                          /* tp_repr */
+    0,                                          /* tp_as_number */
+    0,                                          /* tp_as_sequence */
+    0,                                          /* tp_as_mapping */
+    0,                                          /* tp_hash */
+    0,                                          /* tp_call */
+    0,                                          /* tp_str */
+    PyObject_GenericGetAttr,                    /* tp_getattro */
+    0,                                          /* tp_setattro */
+    0,                                          /* tp_as_buffer */
+    Py_TPFLAGS_DEFAULT | Py_TPFLAGS_HAVE_GC,    /* tp_flags */
+    0,                                          /* tp_doc */
+    async_gen_yield_from_traverse,              /* tp_traverse */
+    async_gen_yield_from_clear,                 /* tp_clear */
+    0,                                          /* tp_richcompare */
+    0,                                          /* tp_weaklistoffset */
+    PyObject_SelfIter,                          /* tp_iter */
+    async_gen_yield_from_iternext,              /* tp_iternext */
+    0,                                          /* tp_methods */
+    0,                                          /* tp_members */
+    0,                                          /* tp_getset */
+    0,                                          /* tp_base */
+    0,                                          /* tp_dict */
+    0,                                          /* tp_descr_get */
+    0,                                          /* tp_descr_set */
+    0,                                          /* tp_dictoffset */
+    0,                                          /* tp_init */
+    0,                                          /* tp_alloc */
+    0,                                          /* tp_new */
+};
+
+
+PyObject *
+_PyAsyncGenYieldFrom_New(PyThreadState *tstate, PyObject *iterator)
+{
+    assert(tstate != NULL);
+    assert(iterator != NULL);
+    _PyAsyncGenYieldFrom *yield_from = PyObject_GC_New(_PyAsyncGenYieldFrom,
+                                                      &_PyAsyncGenYieldFrom_Type);
+    if (yield_from == NULL) {
+        return NULL;
+    }
+    yield_from->agyf_iterator = Py_NewRef(iterator);
+    _PyObject_GC_TRACK((PyObject *)yield_from);
+    return (PyObject *)yield_from;
+}

Python/codegen.c

@@ -5404,10 +5404,11 @@ codegen_visit_expr(compiler *c, expr_ty e)
         if (!_PyST_IsFunctionLike(SYMTABLE_ENTRY(c))) {
             return _PyCompile_Error(c, loc, "'yield from' outside function");
         }
+
+        VISIT(c, expr, e->v.YieldFrom.value);
         if (SCOPE_TYPE(c) == COMPILE_SCOPE_ASYNC_FUNCTION) {
-            return _PyCompile_Error(c, loc, "'yield from' inside async function");
+            ADDOP_I(c, loc, CALL_INTRINSIC_1, INSTRINSIC_ASYNC_GEN_WRAP_YIELD_FROM);
         }
-        VISIT(c, expr, e->v.YieldFrom.value);
         ADDOP(c, loc, GET_YIELD_FROM_ITER);
         ADDOP_LOAD_CONST(c, loc, Py_None);
         ADD_YIELD_FROM(c, loc, 0);

Python/intrinsics.c

@@ -219,6 +219,7 @@ _PyIntrinsics_UnaryFunctions[] = {
     INTRINSIC_FUNC_ENTRY(INTRINSIC_TYPEVARTUPLE, _Py_make_typevartuple)
     INTRINSIC_FUNC_ENTRY(INTRINSIC_SUBSCRIPT_GENERIC, _Py_subscript_generic)
     INTRINSIC_FUNC_ENTRY(INTRINSIC_TYPEALIAS, _Py_make_typealias)
+    INTRINSIC_FUNC_ENTRY(INSTRINSIC_ASYNC_GEN_WRAP_YIELD_FROM, _PyAsyncGenYieldFrom_New)
 };