code: function validIdOrProp(token) {
                      if (!token) {
                          return false;
                      }
                      if (token.string === ".") {
                          return true;
                      }
                      var type = token.type;
                      if (type === "variable-2" || type === "variable" || type === "property") {
                          return true;
                      }
  
                      return false;
                  }
docs: helper function to decide if the tokens on the RHS of an assignment
  look like an identifier, or member expr.