REGEXP_FILE
  RegExpPatternImpl: <a|*>
    RegExpBranchImpl: <a>
      RegExpCharImpl: <a>
        PsiElement(CHARACTER)('a')
    PsiElement(UNION)('|')
    RegExpBranchImpl: <*>
      PsiErrorElement:Dangling quantifier '*'
        <empty list>
      PsiElement(STAR)('*')