Fix _format_coroutine for coroutine-like objects without __name__

Some built-in coroutine-like objects might not have __name__ or
__qualname__. A good example of such are 'asend', 'aclose' and
'athrow' coroutine methods of asynchronous generators.

Author: 1st1

asyncio/coroutines.py

@@ -262,8 +262,12 @@ def _format_coroutine(coro):
     assert iscoroutine(coro)
 
     if not hasattr(coro, 'cr_code') and not hasattr(coro, 'gi_code'):
-        # Most likely a Cython coroutine.
-        coro_name = getattr(coro, '__qualname__', coro.__name__)
+        # Most likely a built-in type or a Cython coroutine.
+
+        # Built-in types might not have __qualname__ or __name__.
+        coro_name = getattr(
+            coro, '__qualname__',
+            getattr(coro, '__name__', type(coro).__name__))
         coro_name = '{}()'.format(coro_name)
 
         running = False

tests/test_events.py

@@ -2384,8 +2384,6 @@ def test_coroutine_like_object_debug_formatting(self):
         # (such as ones compiled with Cython).
 
         class Coro:
-            __name__ = 'AAA'
-
             def send(self, v):
                 pass
 
@@ -2399,6 +2397,7 @@ def __await__(self):
                 pass
 
         coro = Coro()
+        coro.__name__ = 'AAA'
         self.assertTrue(asyncio.iscoroutine(coro))
         self.assertEqual(coroutines._format_coroutine(coro), 'AAA()')
 
@@ -2408,6 +2407,11 @@ def __await__(self):
         coro.cr_running = True
         self.assertEqual(coroutines._format_coroutine(coro), 'BBB() running')
 
+        coro = Coro()
+        # Some coroutines might not have '__name__', such as
+        # built-in async_gen.asend().
+        self.assertEqual(coroutines._format_coroutine(coro), 'Coro()')
+
 
 class TimerTests(unittest.TestCase):