REGEXP_FILE
  RegExpPatternImpl: <(?x)abc #foo \q bar
# foo
(?-xi)xyz(?i:ABC)>
    RegExpBranchImpl: <(?x)abc #foo \q bar
# foo
(?-xi)xyz(?i:ABC)>
      RegExpSetOptionsImpl: <(?x)>
        PsiElement(SET_OPTIONS)('(?')
        RegExpOptionsImpl: <x>
          PsiElement(OPTIONS_ON)('x')
        PsiElement(GROUP_END)(')')
      RegExpCharImpl: <a>
        PsiElement(CHARACTER)('a')
      RegExpCharImpl: <b>
        PsiElement(CHARACTER)('b')
      RegExpCharImpl: <c>
        PsiElement(CHARACTER)('c')
      PsiWhiteSpace(' ')
      PsiComment(COMMENT)('#foo \q bar')
      PsiWhiteSpace('\n')
      PsiComment(COMMENT)('# foo')
      PsiWhiteSpace('\n')
      RegExpSetOptionsImpl: <(?-xi)>
        PsiElement(SET_OPTIONS)('(?')
        RegExpOptionsImpl: <-xi>
          PsiElement(OPTIONS_OFF)('-xi')
        PsiElement(GROUP_END)(')')
      RegExpCharImpl: <x>
        PsiElement(CHARACTER)('x')
      RegExpCharImpl: <y>
        PsiElement(CHARACTER)('y')
      RegExpCharImpl: <z>
        PsiElement(CHARACTER)('z')
      RegExpGroupImpl: <(?i:ABC)>
        PsiElement(SET_OPTIONS)('(?')
        RegExpOptionsImpl: <i>
          PsiElement(OPTIONS_ON)('i')
        PsiElement(COLON)(':')
        RegExpPatternImpl: <ABC>
          RegExpBranchImpl: <ABC>
            RegExpCharImpl: <A>
              PsiElement(CHARACTER)('A')
            RegExpCharImpl: <B>
              PsiElement(CHARACTER)('B')
            RegExpCharImpl: <C>
              PsiElement(CHARACTER)('C')
        PsiElement(GROUP_END)(')')