transformLeftHandSideExpression_(tree) {
    switch (tree.type) {
      case ARRAY_LITERAL:
      case OBJECT_LITERAL:
        resetScanner(tree.location.start.offset);
        // If we fail to parse as an AssignmentPattern then
        // parseAssignmentPattern_ will take care reporting errors.
        return this.parseAssignmentPattern_();
    }
    return tree;
  }
Transforms a LeftHandSideExpression into a AssignmentPattern if possible.
This returns the transformed tree if it parses as an AssignmentPattern,
otherwise it returns the original tree.
@param {ParseTree} tree
@return {ParseTree}