REGEXP_FILE
  RegExpPatternImpl: <(a\w)(?:,(a\w))+>
    RegExpBranchImpl: <(a\w)(?:,(a\w))+>
      RegExpGroupImpl: <(a\w)>
        PsiElement(GROUP_BEGIN)('(')
        RegExpPatternImpl: <a\w>
          RegExpBranchImpl: <a\w>
            RegExpCharImpl: <a>
              PsiElement(CHARACTER)('a')
            RegExpSimpleClassImpl: <\w>
              PsiElement(CHAR_CLASS)('\w')
        PsiElement(GROUP_END)(')')
      RegExpClosureImpl: <(?:,(a\w))+>
        RegExpGroupImpl: <(?:,(a\w))>
          PsiElement(NON_CAPT_GROUP)('(?:')
          RegExpPatternImpl: <,(a\w)>
            RegExpBranchImpl: <,(a\w)>
              RegExpCharImpl: <,>
                PsiElement(CHARACTER)(',')
              RegExpGroupImpl: <(a\w)>
                PsiElement(GROUP_BEGIN)('(')
                RegExpPatternImpl: <a\w>
                  RegExpBranchImpl: <a\w>
                    RegExpCharImpl: <a>
                      PsiElement(CHARACTER)('a')
                    RegExpSimpleClassImpl: <\w>
                      PsiElement(CHAR_CLASS)('\w')
                PsiElement(GROUP_END)(')')
          PsiElement(GROUP_END)(')')
        RegExpQuantifierImpl: <+>
          PsiElement(PLUS)('+')