REGEXP_FILE
  RegExpPatternImpl: <[^]>
    RegExpBranchImpl: <[^]>
      RegExpClassImpl: <[^]>
        PsiElement(CLASS_BEGIN)('[')
        PsiElement(CARET)('^')
        RegExpCharImpl: <]>
          PsiElement(CHARACTER)(']')
        PsiErrorElement:Unclosed character class
          <empty list>