make Coroutine ABC inherit from Awaitable

Cython/Utility/Coroutine.c

@@ -1451,22 +1451,49 @@ Generator.register(_cython_generator_type)
 #endif
 #ifdef __Pyx_Coroutine_USED
                 CSTRING("""\
-def mk_coroutine():
+def mk_awaitable():
     from abc import abstractmethod, ABCMeta
 """)
 #if PY_MAJOR_VERSION >= 3
                 CSTRING("""\
-    class Coroutine(metaclass=ABCMeta):
+    class Awaitable(metaclass=ABCMeta):
 """)
 #else
                 CSTRING("""\
-    class Coroutine(object):
+    class Awaitable(object):
         __metaclass__ = ABCMeta
 """)
 #endif
                 CSTRING("""\
         __slots__ = ()
 
+        @abstractmethod
+        def __await__(self):
+            yield
+
+        @classmethod
+        def __subclasshook__(cls, C):
+            if cls is Awaitable:
+                for B in C.__mro__:
+                    if '__await__' in B.__dict__:
+                        if B.__dict__['__await__']:
+                            return True
+                        break
+            return NotImplemented
+
+    return Awaitable
+
+try:
+    Awaitable = _module.Awaitable
+except AttributeError:
+    Awaitable = _module.Awaitable = mk_awaitable()
+
+def mk_coroutine():
+    from abc import abstractmethod, ABCMeta
+
+    class Coroutine(Awaitable):
+        __slots__ = ()
+
         @abstractmethod
         def send(self, value):
             '''Send a value into the coroutine.
@@ -1497,53 +1524,27 @@ def mk_coroutine():
             else:
                 raise RuntimeError('coroutine ignored GeneratorExit')
 
-    return Coroutine
-
-try:
-    Coroutine = _module.Coroutine
-except AttributeError:
-    Coroutine = _module.Coroutine = mk_coroutine()
-Coroutine.register(_cython_coroutine_type)
-
-def mk_awaitable():
-    from abc import abstractmethod, ABCMeta
-""")
-#if PY_MAJOR_VERSION >= 3
-                CSTRING("""\
-    class Awaitable(metaclass=ABCMeta):
-""")
-#else
-                CSTRING("""\
-    class Awaitable(object):
-        __metaclass__ = ABCMeta
-""")
-#endif
-                CSTRING("""\
-        __slots__ = ()
-
-        @abstractmethod
-        def __await__(self):
-            yield
-
          @classmethod
          def __subclasshook__(cls, C):
-            if cls is Awaitable:
-                for B in C.__mro__:
-                    if '__await__' in B.__dict__:
-                        if B.__dict__['__await__']:
-                            return True
+             if cls is Coroutine:
+                 mro = C.__mro__
+                 for method in ('__await__', 'send', 'throw', 'close'):
+                     for base in mro:
+                         if method in base.__dict__:
                              break
+                     else:
+                         return NotImplemented
+                 return True
              return NotImplemented
 
-    return Awaitable
+
+    return Coroutine
 
 try:
-    Awaitable = _module.Awaitable
+    Coroutine = _module.Coroutine
 except AttributeError:
-    Awaitable = _module.Awaitable = mk_awaitable()
-    Awaitable.register(Coroutine)
-
-Awaitable.register(_cython_coroutine_type)
+    Coroutine = _module.Coroutine = mk_coroutine()
+Coroutine.register(_cython_coroutine_type)
 """)
 #endif
             );