REGEXP_FILE
  RegExpPatternImpl: <[^a\]]>
    RegExpBranchImpl: <[^a\]]>
      RegExpClassImpl: <[^a\]]>
        PsiElement(CLASS_BEGIN)('[')
        PsiElement(CARET)('^')
        RegExpCharImpl: <a>
          PsiElement(CHARACTER)('a')
        RegExpCharImpl: <\]>
          PsiElement(ESC_CHARACTER)('\]')
        PsiElement(CLASS_END)(']')