@ ProgramNode (location: (1,0)-(26,10))
├── locals: []
└── statements:
    @ StatementsNode (location: (1,0)-(26,10))
    └── body: (length: 6)
        ├── @ StringNode (location: (1,0)-(1,10))
        │   ├── flags: ∅
        │   ├── opening_loc: (1,0)-(1,10) = "<<-'  FOO'"
        │   ├── content_loc: (2,0)-(4,0) = "a\nb\n"
        │   ├── closing_loc: (4,0)-(5,0) = "     FOO\n"
        │   └── unescaped: "a\nb\n"
        ├── @ StringNode (location: (6,0)-(6,10))
        │   ├── flags: ∅
        │   ├── opening_loc: (6,0)-(6,10) = "<<-\"  FOO\""
        │   ├── content_loc: (7,0)-(9,0) = "a\nb\n"
        │   ├── closing_loc: (9,0)-(10,0) = "     FOO\n"
        │   └── unescaped: "a\nb\n"
        ├── @ XStringNode (location: (11,0)-(11,10))
        │   ├── flags: ∅
        │   ├── opening_loc: (11,0)-(11,10) = "<<-`  FOO`"
        │   ├── content_loc: (12,0)-(14,0) = "a\nb\n"
        │   ├── closing_loc: (14,0)-(15,0) = "     FOO\n"
        │   └── unescaped: "a\nb\n"
        ├── @ StringNode (location: (16,0)-(16,10))
        │   ├── flags: ∅
        │   ├── opening_loc: (16,0)-(16,10) = "<<-'  FOO'"
        │   ├── content_loc: (17,0)-(19,0) = "a\nb\n"
        │   ├── closing_loc: (19,0)-(20,0) = "  FOO\n"
        │   └── unescaped: "a\nb\n"
        ├── @ InterpolatedStringNode (location: (21,0)-(21,10))
        │   ├── flags: ∅
        │   ├── opening_loc: (21,0)-(21,10) = "<<~'  FOO'"
        │   ├── parts: (length: 2)
        │   │   ├── @ StringNode (location: (22,0)-(23,0))
        │   │   │   ├── flags: frozen
        │   │   │   ├── opening_loc: ∅
        │   │   │   ├── content_loc: (22,0)-(23,0) = "a\n"
        │   │   │   ├── closing_loc: ∅
        │   │   │   └── unescaped: "a\n"
        │   │   └── @ StringNode (location: (23,0)-(24,0))
        │   │       ├── flags: frozen
        │   │       ├── opening_loc: ∅
        │   │       ├── content_loc: (23,0)-(24,0) = "b\n"
        │   │       ├── closing_loc: ∅
        │   │       └── unescaped: "b\n"
        │   └── closing_loc: (24,0)-(25,0) = "     FOO\n"
        └── @ InterpolatedStringNode (location: (26,0)-(26,10))
            ├── flags: ∅
            ├── opening_loc: (26,0)-(26,10) = "<<~'  FOO'"
            ├── parts: (length: 2)
            │   ├── @ StringNode (location: (27,0)-(28,0))
            │   │   ├── flags: frozen
            │   │   ├── opening_loc: ∅
            │   │   ├── content_loc: (27,0)-(28,0) = "a\n"
            │   │   ├── closing_loc: ∅
            │   │   └── unescaped: "a\n"
            │   └── @ StringNode (location: (28,0)-(29,0))
            │       ├── flags: frozen
            │       ├── opening_loc: ∅
            │       ├── content_loc: (28,0)-(29,0) = "b\n"
            │       ├── closing_loc: ∅
            │       └── unescaped: "b\n"
            └── closing_loc: (29,0)-(30,0) = "  FOO\n"