code: function parseVariableIdentifier() {
          var token, startToken;
  
          startToken = lookahead;
          token = lex();
  
          if (token.type !== Token.Identifier) {
              throwUnexpected(token);
          }
  
          return delegate.markEnd(delegate.createIdentifier(token.value), startToken);
      }
docs: 12.2 Variable Statement