REGEXP_FILE
  RegExpPatternImpl: <[a-[b>
    RegExpBranchImpl: <[a-[b>
      RegExpClassImpl: <[a-[b>
        PsiElement(CLASS_BEGIN)('[')
        RegExpCharImpl: <a>
          PsiElement(CHARACTER)('a')
        RegExpCharImpl: <->
          PsiElement(MINUS)('-')
        RegExpClassImpl: <[b>
          PsiElement(CLASS_BEGIN)('[')
          RegExpCharImpl: <b>
            PsiElement(CHARACTER)('b')
          PsiErrorElement:Unclosed character class
            <empty list>