Deprecate custom node types during collection by using special names

changelog/3616.deprecation.rst

@@ -9,3 +9,10 @@ The following accesses have been documented as deprecated for years, but are now
 
 * ``request.cached_setup``, this was the precursor of the setup/teardown mechanism available to fixtures. You can
   consult `funcarg comparision section in the docs <https://docs.pytest.org/en/latest/funcarg_compare.html>`_.
+
+* Using objects named ``"Class"`` as a way to customize the type of nodes that are collected in ``Collector``
+  subclasses has been deprecated. Users instead should use ``pytest_collect_make_item`` to customize node types during
+  collection.
+
+  This issue should affect only advanced plugins who create new collection types, so if you see this warning
+  message please contact the authors so they can change the code.

src/_pytest/nodes.py

@@ -130,10 +130,13 @@ class Node(object):
             return getattr(__import__("pytest"), name)
         else:
             cls = getattr(self, name)
-            # TODO: reenable in the features branch
-            # warnings.warn("use of node.%s is deprecated, "
-            #    "use pytest_pycollect_makeitem(...) to create custom "
-            #    "collection nodes" % name, category=DeprecationWarning)
+            msg = (
+                'use of special named "%s" objects in collectors of type "%s" to '
+                "customize the created nodes is deprecated. "
+                "Use pytest_pycollect_makeitem(...) to create custom "
+                "collection nodes instead." % (name, type(self).__name__)
+            )
+            self.warn(RemovedInPytest4Warning(msg))
         return cls
 
     def __repr__(self):

testing/deprecated_test.py

@@ -68,6 +68,36 @@ def test_cached_setup_deprecation(testdir):
     )
 
 
+def test_custom_class_deprecation(testdir):
+    testdir.makeconftest(
+        """
+        import pytest
+
+        class MyModule(pytest.Module):
+
+            class Class(pytest.Class):
+                pass
+
+        def pytest_pycollect_makemodule(path, parent):
+            return MyModule(path, parent)
+    """
+    )
+    testdir.makepyfile(
+        """
+        class Test:
+            def test_foo(self):
+                pass
+    """
+    )
+    result = testdir.runpytest()
+    result.stdout.fnmatch_lines(
+        [
+            '*test_custom_class_deprecation.py:1:*"Class" objects in collectors of type "MyModule*',
+            "*1 passed, 1 warnings in*",
+        ]
+    )
+
+
 @pytest.mark.filterwarnings("default")
 def test_funcarg_prefix_deprecation(testdir):
     testdir.makepyfile(