register __class__ cell var for class def scope

- special handling for __class__ variable defined in a Class scope

- add relevant unittest for the special __class__ attribute

Author: cosminbasca

graalpython/com.oracle.graal.python.test/src/tests/test_object.py

@@ -1,4 +1,4 @@
-# Copyright (c) 2018, Oracle and/or its affiliates. All rights reserved.
+# Copyright (c) 2018, 2019, Oracle and/or its affiliates. All rights reserved.
 # DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 #
 # The Universal Permissive License (UPL), Version 1.0
@@ -128,3 +128,26 @@ def get_non_existing_attr():
     assert m1.my_attr == 10
     assert "my_attr" not in m1.__dict__
     assert m1.d == 10
+
+
+def test_class_attr():
+    class AAA:
+        def foo(self):
+            assert __class__ == AAA
+            assert self.__class__ == AAA
+
+    class BBB:
+        pass
+
+    class CCC(AAA):
+        def getclass(self):
+            return BBB
+
+        __class__ = property(getclass)
+
+        def bar(self):
+            assert __class__ == CCC
+            assert self.__class__ == BBB
+
+    AAA().foo()
+    CCC().bar()

graalpython/com.oracle.graal.python/src/com/oracle/graal/python/parser/PythonTreeTranslator.java

@@ -1760,7 +1760,7 @@ public Object visitClassdef(Python3Parser.ClassdefContext ctx) {
         visitCallArglist(ctx.arglist(), argumentNodes, keywords, splatArguments);
 
         environment.pushScope(ctx.scope);
-
+        environment.registerSpecialClassCellVar();
         ExpressionNode body = asClassBody(ctx.suite().accept(this), qualName);
         ClassBodyRootNode classBodyRoot = factory.createClassBodyRoot(deriveSourceSection(ctx), className, environment.getCurrentFrame(), body, environment.getExecutionCellSlots());
         RootCallTarget ct = Truffle.getRuntime().createCallTarget(classBodyRoot);
@@ -1778,7 +1778,8 @@ public Object visitClassdef(Python3Parser.ClassdefContext ctx) {
 
         ReadNode tempLocal = environment.makeTempLocalVariable();
         ExpressionNode newClass = ((ExpressionNode) tempLocal).withSideEffect(
-                        factory.createBlock(tempLocal.makeWriteNode(classDef), factory.createWriteCellVar((ExpressionNode) tempLocal, classBodyRoot, __CLASS__)));
+                        factory.createBlock(tempLocal.makeWriteNode(classDef),
+                                        factory.createWriteCellVar((ExpressionNode) tempLocal, classBodyRoot, __CLASS__)));
         return read.makeWriteNode(newClass);
     }
 

graalpython/com.oracle.graal.python/src/com/oracle/graal/python/parser/TranslationEnvironment.java

@@ -281,6 +281,9 @@ private ReadNode findVariableNodeClass(String name) {
         if (isCellInCurrentScope(name)) {
             cellSlot = currentScope.findFrameSlot(name);
         }
+        if (name.equals(__CLASS__)) {
+            return (ReadNode) factory.createReadClassAttributeNode(name, null, currentScope.isFreeVar(name));
+        }
         return (ReadNode) factory.createReadClassAttributeNode(name, cellSlot, currentScope.isFreeVar(name));
     }