Description: Add filename to classes
 Add filename from class-defining code object to classes as __filename__
Author: Thomas Viehmann <tv@beamnet.de>

--- a/Python/bltinmodule.c
+++ b/Python/bltinmodule.c
@@ -36,6 +36,7 @@
 
 _Py_IDENTIFIER(__builtins__);
 _Py_IDENTIFIER(__dict__);
+_Py_IDENTIFIER(__filename__);
 _Py_IDENTIFIER(__prepare__);
 _Py_IDENTIFIER(__round__);
 _Py_IDENTIFIER(encoding);
@@ -58,6 +59,7 @@
     PyObject *cls = NULL, *cell = NULL;
     Py_ssize_t nargs;
     int isclass = 0;   /* initialize to prevent gcc warning */
+    int err = 0;
 
     assert(args != NULL);
     if (!PyTuple_Check(args)) {
@@ -178,6 +180,19 @@
                              NULL, 0, NULL, 0, NULL, 0, NULL,
                              PyFunction_GET_CLOSURE(func));
     if (cell != NULL) {
+        if (PyDict_CheckExact(ns)) {
+            err = _PyDict_SetItemId(ns, &PyId___filename__, ((PyCodeObject*) PyFunction_GET_CODE(func))->co_filename);
+        }
+        else {
+            PyObject *filename_str = _PyUnicode_FromId(&PyId___filename__);
+            if (filename_str == NULL) {
+                goto error;
+            }
+            err = PyObject_SetItem(ns, filename_str, ((PyCodeObject*) PyFunction_GET_CODE(func))->co_filename);
+        }
+        if (err != 0) {
+            goto error;
+        }
         PyObject *margs[3] = {name, bases, ns};
         cls = _PyObject_FastCallDict(meta, margs, 3, mkw);
         if (cls != NULL && PyType_Check(cls) && PyCell_Check(cell)) {
--- a/Lib/test/test_descr.py
+++ b/Lib/test/test_descr.py
@@ -4688,8 +4688,8 @@
         self.assertNotIsInstance(it, list)
         keys = list(it)
         keys.sort()
-        self.assertEqual(keys, ['__dict__', '__doc__', '__module__',
-                                '__weakref__', 'meth'])
+        self.assertEqual(keys, ['__dict__', '__doc__', '__filename__',
+                                '__module__', '__weakref__', 'meth'])
 
     @unittest.skipIf(hasattr(sys, 'gettrace') and sys.gettrace(),
                         'trace function introduces __local__')
@@ -4698,7 +4698,7 @@
         it = self.C.__dict__.values()
         self.assertNotIsInstance(it, list)
         values = list(it)
-        self.assertEqual(len(values), 5)
+        self.assertEqual(len(values), 6)
 
     @unittest.skipIf(hasattr(sys, 'gettrace') and sys.gettrace(),
                         'trace function introduces __local__')
@@ -4708,8 +4708,8 @@
         self.assertNotIsInstance(it, list)
         keys = [item[0] for item in it]
         keys.sort()
-        self.assertEqual(keys, ['__dict__', '__doc__', '__module__',
-                                '__weakref__', 'meth'])
+        self.assertEqual(keys, ['__dict__', '__doc__', '__filename__',
+                                '__module__', '__weakref__', 'meth'])
 
     def test_dict_type_with_metaclass(self):
         # Testing type of __dict__ when metaclass set...
--- a/Lib/test/test_metaclass.py
+++ b/Lib/test/test_metaclass.py
@@ -145,7 +145,8 @@
 
     >>> class LoggingDict(dict):
     ...     def __setitem__(self, key, value):
-    ...         print("d[%r] = %r" % (key, value))
+    ...         if key != '__filename__':
+    ...             print("d[%r] = %r" % (key, value))
     ...         dict.__setitem__(self, key, value)
     ...
     >>> class Meta(type):
@@ -169,7 +170,7 @@
 
     >>> def meta(name, bases, namespace, **kwds):
     ...     print("meta:", name, bases)
-    ...     print("ns:", sorted(namespace.items()))
+    ...     print("ns:", sorted([(k, v) for k, v in namespace.items() if k != "__filename__"]))
     ...     print("kw:", sorted(kwds.items()))
     ...     return namespace
     ...
@@ -182,7 +183,7 @@
     kw: []
     >>> type(C) is dict
     True
-    >>> print(sorted(C.items()))
+    >>> print(sorted([(k, v) for k, v in C.items() if k != "__filename__"]))
     [('__module__', 'test.test_metaclass'), ('__qualname__', 'C'), ('a', 42), ('b', 24)]
     >>>
 
--- a/Lib/inspect.py
+++ b/Lib/inspect.py
@@ -647,6 +647,8 @@
             return object.__file__
         raise TypeError('{!r} is a built-in module'.format(object))
     if isclass(object):
+        if hasattr(object, '__filename__'):
+            return object.__filename__
         if hasattr(object, '__module__'):
             object = sys.modules.get(object.__module__)
             if hasattr(object, '__file__'):
--- a/Lib/typing.py
+++ b/Lib/typing.py
@@ -1681,7 +1681,8 @@ class _ProtocolMeta(GenericMeta):
                             attr != '__orig_bases__' and
                             attr != '__extra__' and
                             attr != '__tree_hash__' and
-                            attr != '__module__'):
+                            attr != '__module__' and
+                            attr != '__filename__'):
                         attrs.add(attr)
 
         return attrs
@@ -2121,7 +2122,7 @@ _prohibited = ('__new__', '__init__', '_
                '_fields', '_field_defaults', '_field_types',
                '_make', '_replace', '_asdict', '_source')
 
-_special = ('__module__', '__name__', '__qualname__', '__annotations__')
+_special = ('__filename__', '__module__', '__name__', '__qualname__', '__annotations__')
 
 
 class NamedTupleMeta(type):