on setSuperClass fix subclasses in old base classes

Author: tomasstupka

graalpython/com.oracle.graal.python/src/com/oracle/graal/python/builtins/objects/type/PythonManagedClass.java

@@ -230,7 +230,7 @@ public void setSuperClass(PythonAbstractClass... newBaseClasses) {
         PythonAbstractClass[] oldBaseClasses = getBaseClasses();
         Object[] oldMRO = this.methodResolutionOrder.getInternalArray();
 
-        Set<PythonAbstractClass> subclasses = getSubClasses();
+        Set<PythonAbstractClass> subclasses = GetSubclassesNode.getUncached().execute(this);
         PythonAbstractClass[] subclassesArray = subclasses.toArray(new PythonAbstractClass[subclasses.size()]);
         Object[][] oldSubClasssMROs = new Object[subclasses.size()][];
         for (int i = 0; i < subclassesArray.length; i++) {
@@ -241,28 +241,28 @@ public void setSuperClass(PythonAbstractClass... newBaseClasses) {
         }
 
         try {
-            for (PythonAbstractClass base : newBaseClasses) {
-                if (base != null) {
-                    GetSubclassesNode.getUncached().execute(base).add(this);
-                }
-            }
-
+            // for what follows see also typeobject.c#type_set_bases()
             this.baseClasses = newBaseClasses;
             this.methodResolutionOrder.setInternalArrayObject(ComputeMroNode.doSlowPath(this));
             this.methodResolutionOrder.lookupChanged();
 
+            for (PythonAbstractClass scls : subclasses) {
+                if (scls instanceof PythonManagedClass) {
+                    PythonManagedClass pmc = (PythonManagedClass) scls;
+                    pmc.methodResolutionOrder.setInternalArrayObject(ComputeMroNode.doSlowPath(scls));
+                    pmc.methodResolutionOrder.lookupChanged();
+                }
+            }
             if (this.baseClasses == newBaseClasses) {
                 // take no action if bases were replaced through reentrance
-                for (PythonAbstractClass scls : subclasses) {
-                    if (scls instanceof PythonManagedClass) {
-                        PythonManagedClass pmc = (PythonManagedClass) scls;
-                        pmc.methodResolutionOrder.setInternalArrayObject(ComputeMroNode.doSlowPath(scls));
-                        pmc.methodResolutionOrder.lookupChanged();
+                for (PythonAbstractClass base : oldBaseClasses) {
+                    if (base instanceof PythonManagedClass) {
+                        GetSubclassesNode.getUncached().execute(base).remove(this);
                     }
                 }
-                for (PythonAbstractClass obc : oldBaseClasses) {
-                    if (obc instanceof PythonManagedClass) {
-                        ((PythonManagedClass) obc).getSubClasses().remove(this);
+                for (PythonAbstractClass base : newBaseClasses) {
+                    if (base instanceof PythonManagedClass) {
+                        GetSubclassesNode.getUncached().execute(base).add(this);
                     }
                 }
             }