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