REGEXP_FILE
  RegExpPatternImpl: <a?+>
    RegExpBranchImpl: <a?+>
      RegExpClosureImpl: <a?+>
        RegExpCharImpl: <a>
          PsiElement(CHARACTER)('a')
        RegExpQuantifierImpl: <?+>
          PsiElement(QUEST)('?')
          PsiElement(PLUS)('+')