REGEXP_FILE
  RegExpPatternImpl: <a[\p{IsDigit}\p{IsAlpha}]b>
    RegExpBranchImpl: <a[\p{IsDigit}\p{IsAlpha}]b>
      RegExpCharImpl: <a>
        PsiElement(CHARACTER)('a')
      RegExpClassImpl: <[\p{IsDigit}\p{IsAlpha}]>
        PsiElement(CLASS_BEGIN)('[')
        RegExpPropertyImpl: <\p{IsDigit}>
          PsiElement(PROPERTY)('\p')
          PsiElement(LBRACE)('{')
          PsiElement(NAME)('IsDigit')
          PsiElement(RBRACE)('}')
        RegExpPropertyImpl: <\p{IsAlpha}>
          PsiElement(PROPERTY)('\p')
          PsiElement(LBRACE)('{')
          PsiElement(NAME)('IsAlpha')
          PsiElement(RBRACE)('}')
        PsiElement(CLASS_END)(']')
      RegExpCharImpl: <b>
        PsiElement(CHARACTER)('b')