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