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