message: error-detector code style tweak
diff: import { dirRE, onRE } from './parser/index'
  -// operators like typeof, instanceof and in are allowed
  +// these keywords should not appear inside expressions, but operators like
  +// typeof, instanceof and in are allowed
  const prohibitedKeywordRE = new RegExp('\\b' + (
  'do,if,for,let,new,try,var,case,else,with,await,break,catch,class,const,' +
  'super,throw,while,yield,delete,export,import,return,switch,default,' +
  'extends,finally,continue,debugger,function,arguments'
  ).split(',').join('\\b|\\b') + '\\b')
  +
  +// these unary operators should not be used as property/method names
  const unaryOperatorsRE = new RegExp('\\b' + (
  'delete,typeof,void'
  ).split(',').join('\\s*\\([^\\)]*\\)|\\b') + '\\s*\\([^\\)]*\\)')
  +
  // check valid identifier for v-for
  const identRE = /[A-Za-z_$][\w$]*/
  +
  // strip strings in expressions
  const stripStringRE = /'(?:[^'\\]|\\.)*'|"(?:[^"\\]|\\.)*"|`(?:[^`\\]|\\.)*\$\{|\}(?:[^`\\]|\\.)*`|`(?:[^`\\]|\\.)*`/g
  