REGEXP_FILE
  RegExpPatternImpl: <[&&&&a]>
    RegExpBranchImpl: <[&&&&a]>
      RegExpClassImpl: <[&&&&a]>
        PsiElement(CLASS_BEGIN)('[')
        RegExpIntersectionImpl: <&&&&a>
          PsiElement(ANDAND)('&&')
          PsiErrorElement:Character class expected
            <empty list>
          PsiElement(ANDAND)('&&')
          RegExpCharImpl: <a>
            PsiElement(CHARACTER)('a')
        PsiElement(CLASS_END)(']')