Fix #27431.

The layer class was incorrectly tracked by layer._layer, which should
only track layer instance. This should be mitigated once b/110718070 is
fixed.

PiperOrigin-RevId: 243103748

tensorflow/python/keras/engine/base_layer_test.py

@@ -541,6 +541,19 @@ class NestedTrackingTest(test.TestCase):
 
     self.assertEqual([layer.v], layer.variables)
 
+  def test_layer_class_not_tracked_as_sublayer(self):
+    # See https://github.com/tensorflow/tensorflow/issues/27431 for details.
+
+    class LayerWithClassAttribute(keras.layers.Layer):
+
+      def __init__(self):
+        super(LayerWithClassAttribute, self).__init__()
+        self.layer_fn = keras.layers.Dense
+
+    layer = LayerWithClassAttribute()
+    self.assertEmpty(layer.variables)
+    self.assertEmpty(layer.submodules)
+
 
 @test_util.run_all_in_graph_and_eager_modes
 class NameScopingTest(keras_parameterized.TestCase):

tensorflow/python/training/tracking/layer_utils.py

@@ -27,14 +27,15 @@ from tensorflow.python.training.tracking import object_identity
 def is_layer(obj):
   """Implicit check for Layer-like objects."""
   # TODO(b/110718070): Replace with isinstance(obj, base_layer.Layer).
-  return hasattr(obj, "_is_layer")
+  return hasattr(obj, "_is_layer") and not isinstance(obj, type)
 
 
 def has_weights(obj):
   """Implicit check for Layer-like objects."""
   # TODO(b/110718070): Replace with isinstance(obj, base_layer.Layer).
   return (hasattr(obj, "trainable_weights")
-          and hasattr(obj, "non_trainable_weights"))
+          and hasattr(obj, "non_trainable_weights")
+          and not isinstance(obj, type))
 
 
 def filter_empty_layer_containers(layer_list):