REGEXP_FILE
  RegExpPatternImpl: <a{>
    RegExpBranchImpl: <a{>
      RegExpClosureImpl: <a{>
        RegExpCharImpl: <a>
          PsiElement(CHARACTER)('a')
        RegExpQuantifierImpl: <{>
          PsiElement(LBRACE)('{')
          PsiErrorElement:Number expected
            <empty list>