How to use the traceur/src/staticsemantics/PropName.propName function in traceur

tree.elements.forEach(function(elementTree) {
      if (elementTree.type === PROPERTY_METHOD_ASSIGNMENT &&
          !elementTree.isStatic &&
          propName(elementTree) === CONSTRUCTOR) {

        // Store constructor argument types,
        // so that we can use them to set the types of simple-assigned fields.
        elementTree.parameterList.parameters.forEach(function(p) {
          var binding = p.parameter.binding;
          if (binding.identifierToken) {
            argumentTypesMap[binding.identifierToken.value] = p.typeAnnotation;
          }
        });

        // Rename "constructor" to the class name.
        elementTree.name.literalToken.value = className;

        // Collect all fields, defined in the constructor.
        elementTree.body.statements.forEach(function(statement) {
          if (statement.expression.type === BINARY_EXPRESSION &&

tree.elements.forEach(function(elementTree, index) {
      if (elementTree.type === PROPERTY_METHOD_ASSIGNMENT &&
          !elementTree.isStatic &&
          propName(elementTree) === CONSTRUCTOR) {

        hasConstructor = true;
        isConst = elementTree.annotations.some(that._isConstAnnotation);

        // Store constructor argument types,
        // so that we can use them to set the types of simple-assigned fields.
        elementTree.parameterList.parameters.forEach(function(p) {
          var binding = p.parameter.binding;
          if (binding && binding.identifierToken) {
            argumentTypesMap[binding.identifierToken.value] = p.typeAnnotation;
          }
        });

        // Rename "constructor" to the class name.
        elementTree.name.literalToken.value = className;