REGEXP_FILE
  RegExpPatternImpl: <a\p}>
    RegExpBranchImpl: <a\p}>
      RegExpCharImpl: <a>
        PsiElement(CHARACTER)('a')
      RegExpPropertyImpl: <\p>
        PsiElement(PROPERTY)('\p')
        PsiErrorElement:'{' or category shorthand expected
          <empty list>
      RegExpCharImpl: <}>
        PsiElement(CHARACTER)('}')