REGEXP_FILE
  RegExpPatternImpl: <(ac*)c*d[ac]*\1>
    RegExpBranchImpl: <(ac*)c*d[ac]*\1>
      RegExpGroupImpl: <(ac*)>
        PsiElement(GROUP_BEGIN)('(')
        RegExpPatternImpl: <ac*>
          RegExpBranchImpl: <ac*>
            RegExpCharImpl: <a>
              PsiElement(CHARACTER)('a')
            RegExpClosureImpl: <c*>
              RegExpCharImpl: <c>
                PsiElement(CHARACTER)('c')
              RegExpQuantifierImpl: <*>
                PsiElement(STAR)('*')
        PsiElement(GROUP_END)(')')
      RegExpClosureImpl: <c*>
        RegExpCharImpl: <c>
          PsiElement(CHARACTER)('c')
        RegExpQuantifierImpl: <*>
          PsiElement(STAR)('*')
      RegExpCharImpl: <d>
        PsiElement(CHARACTER)('d')
      RegExpClosureImpl: <[ac]*>
        RegExpClassImpl: <[ac]>
          PsiElement(CLASS_BEGIN)('[')
          RegExpCharImpl: <a>
            PsiElement(CHARACTER)('a')
          RegExpCharImpl: <c>
            PsiElement(CHARACTER)('c')
          PsiElement(CLASS_END)(']')
        RegExpQuantifierImpl: <*>
          PsiElement(STAR)('*')
      RegExpBackrefImpl: <\1>
        PsiElement(BACKREF)('\1')