Return new classes when inferring calls to type(name, bases, ns) and its subtypes.

3 files changed, 40 insertions, 1 deletions

diff --git a/ChangeLog b/ChangeLog
index ae4d7bc..ef24ed5 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -2,6 +2,10 @@ Change log for the astroid package (used to be astng)
 =====================================================
 
 --
+   
+    * infer_call_result called on a subtype of the builtin type will now
+      return a new `Class` rather than an `Instance`.
+
     * `Class.metaclass()` now handles module-level __metaclass__ declaration
       on python 2, and no longer looks at the __metaclass__ class attribute on
       python 3.
diff --git a/scoped_nodes.py b/scoped_nodes.py
index f070837..6b09b9d 100644
--- a/scoped_nodes.py
+++ b/scoped_nodes.py
@@ -851,9 +851,32 @@ class Class(Statement, LocalsDictNodeNG, FilterStmtsMixin):
     def callable(self):
         return True
 
+    def _is_subtype_of(self, type_name):
+        if self.qname() == type_name:
+            return True
+        for anc in self.ancestors():
+            if anc.qname() == type_name:
+                return True
+
     def infer_call_result(self, caller, context=None):
         """infer what a class is returning when called"""
-        yield Instance(self)
+        if self._is_subtype_of('%s.type' % (BUILTINS,)) and len(caller.args) == 3:
+            name_node = caller.args[0].infer().next()
+            if isinstance(name_node, Const) and isinstance(name_node.value, basestring):
+                name = name_node.value
+            else:
+                yield YES
+                return
+            result = Class(name, None)
+            bases = caller.args[1].infer().next()
+            if isinstance(bases, (Tuple, List)):
+                result.bases = bases.itered()
+            else:
+                result.bases = [YES]
+            result.parent = caller.parent
+            yield result
+        else:
+           yield Instance(self)
 
     def scope_lookup(self, node, name, offset=0):
         if node in self.bases:
diff --git a/test/unittest_scoped_nodes.py b/test/unittest_scoped_nodes.py
index 37ff3be..116b275 100644
--- a/test/unittest_scoped_nodes.py
+++ b/test/unittest_scoped_nodes.py
@@ -852,6 +852,18 @@ def g2():
                 self.assertIsInstance(meta, nodes.Class)
                 self.assertEqual(meta.name, metaclass)
 
+    def test_metaclass_type(self):
+        klass = extract_node("""
+        def with_metaclass(meta, base=object):
+            return meta("NewBase", (base, ), {})
+
+        class ClassWithMeta(with_metaclass(type)): #@
+            pass
+        """)
+        self.assertEqual(
+            ['NewBase', 'object'],
+            [base.name for base in klass.ancestors()])
+
     def test_nonregr_infer_callresult(self):
         astroid = abuilder.string_build(dedent("""
         class Delegate(object):