Fix wrapping into StopIteration of return values in generators and coroutines (#644) (#648)

3 files changed, 18 insertions, 2 deletions

diff --git a/Lib/test/test_coroutines.py b/Lib/test/test_coroutines.py
index 4a327b5..6d63cdb 100644
--- a/Lib/test/test_coroutines.py
+++ b/Lib/test/test_coroutines.py
@@ -975,6 +975,21 @@ class CoroutineTest(unittest.TestCase):
                                     "coroutine is being awaited already"):
             waiter(coro).send(None)
 
+    def test_await_16(self):
+        # See https://bugs.python.org/issue29600 for details.
+
+        async def f():
+            return ValueError()
+
+        async def g():
+            try:
+                raise KeyError
+            except:
+                return await f()
+
+        _, result = run_async(g())
+        self.assertIsNone(result.__context__)
+
     def test_with_1(self):
         class Manager:
             def __init__(self, name):
diff --git a/Misc/NEWS b/Misc/NEWS
index 98b47bd..e56c091 100644
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -10,6 +10,8 @@ Release date: XXXX-XX-XX
 Core and Builtins
 -----------------
 
+- bpo-29600: Fix wrapping coroutine return values in StopIteration.
+
 - Issue #29537: Restore runtime compatibility with bytecode files generated by
   CPython 3.5.0 to 3.5.2, and adjust the eval loop to avoid the problems that
   could be caused by the malformed variant of the BUILD_MAP_UNPACK_WITH_CALL
diff --git a/Objects/genobject.c b/Objects/genobject.c
index d403598..0de5408 100644
--- a/Objects/genobject.c
+++ b/Objects/genobject.c
@@ -466,8 +466,7 @@ _PyGen_SetStopIterationValue(PyObject *value)
     PyObject *e;
 
     if (value == NULL ||
-        (!PyTuple_Check(value) &&
-         !PyObject_TypeCheck(value, (PyTypeObject *) PyExc_StopIteration)))
+        (!PyTuple_Check(value) && !PyExceptionInstance_Check(value)))
     {
         /* Delay exception instantiation if we can */
         PyErr_SetObject(PyExc_StopIteration, value);