ProgramNode(0...13)(
  [],
  StatementsNode(0...13)(
    [InterpolatedStringNode(0...8)(
       (0...1),
       [StringNode(1...3)(nil, (1...3), nil, "a\n"),
        EmbeddedStatementsNode(3...7)((3...5), nil, (6...7))],
       (7...8)
     ),
     TrueNode(9...13)()]
  )
)
