Python: add support for type(self)()

Author: RasmusWL

python/ql/lib/semmle/python/dataflow/new/internal/DataFlowDispatch.qll

@@ -466,7 +466,7 @@ Node classTracker(Class cls) { classTracker(TypeTracker::end(), cls).flowsTo(res
  */
 private TypeTrackingNode classInstanceTracker(TypeTracker t, Class cls) {
   t.start() and
-  result.(CallCfgNode).getFunction() = classTracker(cls)
+  resolveClassCall(result.(CallCfgNode).asCfgNode(), cls)
   or
   exists(TypeTracker t2 | result = classInstanceTracker(t2, cls).track(t2, t)) and
   not result.(ParameterNodeImpl).isParameterOf(_, any(ParameterPosition pp | pp.isSelf()))
@@ -951,6 +951,12 @@ import MethodCalls
  */
 predicate resolveClassCall(CallNode call, Class cls) {
   call.getFunction() = classTracker(cls).asCfgNode()
+  or
+  // `cls()` inside a classmethod (which also contains `type(self)()` inside a method)
+  exists(Class classWithMethod |
+    call.getFunction() = clsTracker(classWithMethod).asCfgNode() and
+    getADirectSuperclass*(cls) = classWithMethod
+  )
 }
 
 /**

python/ql/test/experimental/library-tests/CallGraph/InlineCallGraphTest.expected

@@ -7,7 +7,6 @@ pointsTo_found_typeTracker_notFound
 | code/class_attr_assign.py:10:9:10:27 | ControlFlowNode for Attribute() | my_func |
 | code/class_attr_assign.py:11:9:11:25 | ControlFlowNode for Attribute() | my_func |
 | code/class_attr_assign.py:26:9:26:25 | ControlFlowNode for Attribute() | DummyObject.method |
-| code/class_construction.py:23:1:23:11 | ControlFlowNode for Attribute() | X.foo |
 | code/class_super.py:50:1:50:6 | ControlFlowNode for Attribute() | outside_def |
 | code/conditional_in_argument.py:18:5:18:11 | ControlFlowNode for Attribute() | X.bar |
 | code/func_defined_outside_class.py:21:1:21:11 | ControlFlowNode for Attribute() | A.foo |

python/ql/test/experimental/library-tests/CallGraph/code/class_construction.py

@@ -8,19 +8,19 @@ def foo(self):
 
     def meth(self):
         print("X.meth")
-        return type(self)(42.1) # $ MISSING: tt=X.__init__ tt=Y.__init__
+        return type(self)(42.1) # $ tt=X.__init__ tt=Y.__init__
 
     @classmethod
     def cm(cls):
         print("X.cm")
-        cls(42.2) # $ MISSING: tt=X.__init__ tt=Y.__init__
+        cls(42.2) # $ tt=X.__init__ tt=Y.__init__
 
 x = X(42.0) # $ tt=X.__init__
 x_421 = x.meth() # $ pt,tt=X.meth
 X.cm() # $ pt,tt=X.cm
 x.foo() # $ pt,tt=X.foo
 print()
-x_421.foo() # $ pt=X.foo MISSING: tt=X.foo
+x_421.foo() # $ pt=X.foo tt=X.foo
 print()