[3.12] gh-120200: Fix inspect.iscoroutinefunction(inspect) is True corner case (GH-120214) (#120239)

* [3.12] gh-120200: Fix `inspect.iscoroutinefunction(inspect) is True` corner case (GH-120214)
(cherry picked from commit 10fb1b8)

Co-authored-by: Nikita Sobolev <[email protected]>

Author: sobolevn

Lib/inspect.py

@@ -401,21 +401,21 @@ def isgeneratorfunction(obj):
     return _has_code_flag(obj, CO_GENERATOR)
 
 # A marker for markcoroutinefunction and iscoroutinefunction.
-_is_coroutine_marker = object()
+_is_coroutine_mark = object()
 
 def _has_coroutine_mark(f):
     while ismethod(f):
         f = f.__func__
     f = functools._unwrap_partial(f)
-    return getattr(f, "_is_coroutine_marker", None) is _is_coroutine_marker
+    return getattr(f, "_is_coroutine_marker", None) is _is_coroutine_mark
 
 def markcoroutinefunction(func):
     """
     Decorator to ensure callable is recognised as a coroutine function.
     """
     if hasattr(func, '__func__'):
         func = func.__func__
-    func._is_coroutine_marker = _is_coroutine_marker
+    func._is_coroutine_marker = _is_coroutine_mark
     return func
 
 def iscoroutinefunction(obj):

Lib/test/test_inspect/test_inspect.py

@@ -199,6 +199,7 @@ def test_iscoroutine(self):
             inspect.iscoroutinefunction(
                 functools.partial(functools.partial(
                     gen_coroutine_function_example))))
+        self.assertFalse(inspect.iscoroutinefunction(inspect))
         self.assertFalse(inspect.iscoroutine(gen_coro))
 
         self.assertTrue(