Issue #24400: Resurrect inspect.isawaitable()

collections.abc.Awaitable and collections.abc.Coroutine no longer
use __instancecheck__ hook to detect generator-based coroutines.

inspect.isawaitable() can be used to detect generator-based coroutines
and to distinguish them from regular generator objects.

Lib/inspect.py

@@ -207,6 +207,13 @@ def iscoroutine(object):
     """Return true if the object is a coroutine."""
     return isinstance(object, types.CoroutineType)
 
+def isawaitable(object):
+    """Return true is object can be passed to an ``await`` expression."""
+    return (isinstance(object, types.CoroutineType) or
+            isinstance(object, types.GeneratorType) and
+                object.gi_code.co_flags & CO_ITERABLE_COROUTINE or
+            isinstance(object, collections.abc.Awaitable))
+
 def istraceback(object):
     """Return true if the object is a traceback.