From 1b3e67ecd46908b133f838baf039bfb6f90f2bae Mon Sep 17 00:00:00 2001
From: Mark Dickinson <mdickinson@enthought.com>
Date: Tue, 30 Oct 2018 07:36:46 +0000
Subject: [PATCH] Revert "FIX: Check function attributes upon class creation"

---
 traits/has_traits.py            |  8 ++++----
 traits/tests/test_regression.py | 30 +-----------------------------
 2 files changed, 5 insertions(+), 33 deletions(-)

diff --git a/traits/has_traits.py b/traits/has_traits.py
index 0453d0fc79..54420156ba 100644
--- a/traits/has_traits.py
+++ b/traits/has_traits.py
@@ -547,10 +547,10 @@ def __init__ ( self, cls, class_name, bases, class_dict, is_category ):
                     prefix_list.append( name )
                     prefix_traits[ name ] = value
 
-            elif (( isinstance( value, FunctionType ) or
-                    is_cython_func_or_method(value) ) and
-                   hasattr( value, 'on_trait_change' )):
-                listeners[ name ] = ( 'method', value.on_trait_change )
+            elif isinstance( value, FunctionType ) or is_cython_func_or_method(value):
+                pattern = getattr( value, 'on_trait_change', None )
+                if pattern is not None:
+                    listeners[ name ] = ( 'method', pattern )
 
             elif isinstance( value, property ):
                 class_traits[ name ] = generic_trait
diff --git a/traits/tests/test_regression.py b/traits/tests/test_regression.py
index cd03ca6930..b110fb0d36 100644
--- a/traits/tests/test_regression.py
+++ b/traits/tests/test_regression.py
@@ -11,9 +11,7 @@
     from ..trait_numeric import Array
 
 from ..has_traits import HasTraits, Property, on_trait_change
-from ..trait_types import (
-    Bool, Callable, DelegatesTo, Either, Instance, Int, List
-)
+from ..trait_types import Bool, DelegatesTo, Either, Instance, Int, List
 from ..testing.unittest_tools import unittest
 
 
@@ -234,31 +232,5 @@ def test_on_trait_change_with_list_of_extended_names(self):
         self.assertTrue(model.changed)
 
 
-class TestDerivedClassDefaults(unittest.TestCase):
-
-    def test_function_default(self):
-        # Regression test for enthought/traits#411. Providing a pure Python
-        # default in a child class for a Callable trait declared in the base
-        # class didn't work as expected -- the default value would be silently
-        # ignored.
-
-        # Given
-
-        def square(x):
-            return x ** 2
-
-        class A(HasTraits):
-            f = Callable()
-
-        class B(A):
-            f = square
-
-        # When
-        b = B()
-
-        # Then
-        self.assertEquals(b.f(3), 9)
-
-
 if __name__ == '__main__':
     unittest.main()