gh-94912: Adjusted check for non-standard coroutine function marker. (#100935)

The initial implementation did not correctly identify explicitly
marked class instances.

Follow up to 532aa4e

Author: carltongibson

Lib/inspect.py

@@ -399,8 +399,6 @@ def _has_coroutine_mark(f):
     while ismethod(f):
         f = f.__func__
     f = functools._unwrap_partial(f)
-    if not (isfunction(f) or _signature_is_functionlike(f)):
-        return False
     return getattr(f, "_is_coroutine_marker", None) is _is_coroutine_marker
 
 def markcoroutinefunction(func):

Lib/test/test_inspect.py

@@ -223,6 +223,10 @@ async def __call__(self):
         self.assertFalse(inspect.iscoroutinefunction(Cl))
         # instances with async def __call__ are NOT recognised.
         self.assertFalse(inspect.iscoroutinefunction(Cl()))
+        # unless explicitly marked.
+        self.assertTrue(inspect.iscoroutinefunction(
+            inspect.markcoroutinefunction(Cl())
+        ))
 
         class Cl2:
             @inspect.markcoroutinefunction
@@ -232,6 +236,10 @@ def __call__(self):
         self.assertFalse(inspect.iscoroutinefunction(Cl2))
         # instances with marked __call__ are NOT recognised.
         self.assertFalse(inspect.iscoroutinefunction(Cl2()))
+        # unless explicitly marked.
+        self.assertTrue(inspect.iscoroutinefunction(
+            inspect.markcoroutinefunction(Cl2())
+        ))
 
         class Cl3:
             @inspect.markcoroutinefunction