PEP 0492 -- Coroutines with async and await syntax. Issue #24017.

Include/object.h

@@ -173,6 +173,9 @@ typedef PyObject *(*ssizessizeargfunc)(PyObject *, Py_ssize_t, Py_ssize_t);
 typedef int(*ssizeobjargproc)(PyObject *, Py_ssize_t, PyObject *);
 typedef int(*ssizessizeobjargproc)(PyObject *, Py_ssize_t, Py_ssize_t, PyObject *);
 typedef int(*objobjargproc)(PyObject *, PyObject *, PyObject *);
+typedef PyObject *(*getawaitablefunc) (PyObject *);
+typedef PyObject *(*getaiterfunc) (PyObject *);
+typedef PyObject *(*aiternextfunc) (PyObject *);
 
 #ifndef Py_LIMITED_API
 /* buffer interface */
@@ -301,6 +304,11 @@ typedef struct {
     objobjargproc mp_ass_subscript;
 } PyMappingMethods;
 
+typedef struct {
+    getawaitablefunc am_await;
+    getaiterfunc am_aiter;
+    aiternextfunc am_anext;
+} PyAsyncMethods;
 
 typedef struct {
      getbufferproc bf_getbuffer;
@@ -346,7 +354,7 @@ typedef struct _typeobject {
     printfunc tp_print;
     getattrfunc tp_getattr;
     setattrfunc tp_setattr;
-    void *tp_reserved; /* formerly known as tp_compare */
+    PyAsyncMethods *tp_as_async; /* formerly known as tp_compare or tp_reserved */
     reprfunc tp_repr;
 
     /* Method suites for standard classes */
@@ -453,6 +461,7 @@ typedef struct _heaptypeobject {
     /* Note: there's a dependency on the order of these members
        in slotptr() in typeobject.c . */
     PyTypeObject ht_type;
+    PyAsyncMethods as_async;
     PyNumberMethods as_number;
     PyMappingMethods as_mapping;
     PySequenceMethods as_sequence; /* as_sequence comes after as_mapping,