use str() to convert values toString through polyglot API

Author: timfel

graalpython/com.oracle.graal.python/src/com/oracle/graal/python/PythonLanguage.java

@@ -35,16 +35,16 @@
 
 import com.oracle.graal.python.builtins.Python3Core;
 import com.oracle.graal.python.builtins.objects.PNone;
+import com.oracle.graal.python.builtins.PythonBuiltinClassType;
 import com.oracle.graal.python.builtins.objects.PythonAbstractObject;
 import com.oracle.graal.python.builtins.objects.function.PArguments;
 import com.oracle.graal.python.builtins.objects.function.PBuiltinFunction;
 import com.oracle.graal.python.builtins.objects.function.PKeyword;
-import com.oracle.graal.python.builtins.objects.method.PBuiltinMethod;
-import com.oracle.graal.python.builtins.objects.module.PythonModule;
 import com.oracle.graal.python.builtins.objects.object.PythonObject;
-import com.oracle.graal.python.nodes.BuiltinNames;
+import com.oracle.graal.python.builtins.objects.type.PythonBuiltinClass;
 import com.oracle.graal.python.nodes.NodeFactory;
 import com.oracle.graal.python.nodes.PNode;
+import com.oracle.graal.python.nodes.SpecialMethodNames;
 import com.oracle.graal.python.nodes.call.InvokeNode;
 import com.oracle.graal.python.nodes.control.TopLevelExceptionHandler;
 import com.oracle.graal.python.nodes.expression.ExpressionNode;
@@ -363,12 +363,12 @@ protected Iterable<Scope> findTopScopes(PythonContext context) {
 
     @Override
     protected String toString(PythonContext context, Object value) {
-        final PythonModule builtins = context.getBuiltins();
-        PBuiltinFunction reprMethod = ((PBuiltinMethod) builtins.getAttribute(BuiltinNames.REPR)).getFunction();
+        PythonBuiltinClass strType = context.getCore().lookupType(PythonBuiltinClassType.PString);
+        PBuiltinFunction strConstructor = (PBuiltinFunction) strType.getAttribute(SpecialMethodNames.__NEW__);
         Object[] userArgs = PArguments.create(2);
-        PArguments.setArgument(userArgs, 0, PNone.NONE);
+        PArguments.setArgument(userArgs, 0, strType);
         PArguments.setArgument(userArgs, 1, value);
-        Object res = InvokeNode.create(reprMethod).execute(null, userArgs, PKeyword.EMPTY_KEYWORDS);
+        Object res = InvokeNode.create(strConstructor).execute(null, userArgs, PKeyword.EMPTY_KEYWORDS);
         return res.toString();
     }