bpo-43683: Handle generator entry in bytecode (GH-25138)

* Handle check for sending None to starting generator and coroutine into bytecode.

* Document new bytecode and make it fail gracefully if mis-compiled.

1 files changed, 6 insertions, 21 deletions

diff --git a/Objects/genobject.c b/Objects/genobject.c
index 6998967..b02a558 100644
--- a/Objects/genobject.c
+++ b/Objects/genobject.c
@@ -176,27 +176,12 @@ gen_send_ex2(PyGenObject *gen, PyObject *arg, PyObject **presult,
     }
 
     assert(_PyFrame_IsRunnable(f));
-    if (f->f_lasti == -1) {
-        if (arg && arg != Py_None) {
-            const char *msg = "can't send non-None value to a "
-                              "just-started generator";
-            if (PyCoro_CheckExact(gen)) {
-                msg = NON_INIT_CORO_MSG;
-            }
-            else if (PyAsyncGen_CheckExact(gen)) {
-                msg = "can't send non-None value to a "
-                      "just-started async generator";
-            }
-            PyErr_SetString(PyExc_TypeError, msg);
-            return PYGEN_ERROR;
-        }
-    } else {
-        /* Push arg onto the frame's value stack */
-        result = arg ? arg : Py_None;
-        Py_INCREF(result);
-        gen->gi_frame->f_valuestack[gen->gi_frame->f_stackdepth] = result;
-        gen->gi_frame->f_stackdepth++;
-    }
+    assert(f->f_lasti >= 0 || ((unsigned char *)PyBytes_AS_STRING(f->f_code->co_code))[0] == GEN_START);
+    /* Push arg onto the frame's value stack */
+    result = arg ? arg : Py_None;
+    Py_INCREF(result);
+    gen->gi_frame->f_valuestack[gen->gi_frame->f_stackdepth] = result;
+    gen->gi_frame->f_stackdepth++;
 
     /* Generators always return to their most recent caller, not
      * necessarily their creator. */