@ ProgramNode (location: (0...13))
├── locals: []
└── statements:
    @ StatementsNode (location: (0...13))
    └── body: (length: 1)
        └── @ ArrayNode (location: (0...13))
            ├── elements: (length: 2)
            │   ├── @ InterpolatedSymbolNode (location: (3...7))
            │   │   ├── opening_loc: ∅
            │   │   ├── parts: (length: 1)
            │   │   │   └── @ EmbeddedStatementsNode (location: (3...7))
            │   │   │       ├── opening_loc: (3...5) = "\#{"
            │   │   │       ├── statements:
            │   │   │       │   @ StatementsNode (location: (5...6))
            │   │   │       │   └── body: (length: 1)
            │   │   │       │       └── @ CallNode (location: (5...6))
            │   │   │       │           ├── receiver: ∅
            │   │   │       │           ├── call_operator_loc: ∅
            │   │   │       │           ├── message_loc: (5...6) = "a"
            │   │   │       │           ├── opening_loc: ∅
            │   │   │       │           ├── arguments: ∅
            │   │   │       │           ├── closing_loc: ∅
            │   │   │       │           ├── block: ∅
            │   │   │       │           ├── flags: variable_call
            │   │   │       │           └── name: "a"
            │   │   │       └── closing_loc: (6...7) = "}"
            │   │   └── closing_loc: ∅
            │   └── @ InterpolatedSymbolNode (location: (8...12))
            │       ├── opening_loc: ∅
            │       ├── parts: (length: 1)
            │       │   └── @ EmbeddedStatementsNode (location: (8...12))
            │       │       ├── opening_loc: (8...10) = "\#{"
            │       │       ├── statements:
            │       │       │   @ StatementsNode (location: (10...11))
            │       │       │   └── body: (length: 1)
            │       │       │       └── @ CallNode (location: (10...11))
            │       │       │           ├── receiver: ∅
            │       │       │           ├── call_operator_loc: ∅
            │       │       │           ├── message_loc: (10...11) = "b"
            │       │       │           ├── opening_loc: ∅
            │       │       │           ├── arguments: ∅
            │       │       │           ├── closing_loc: ∅
            │       │       │           ├── block: ∅
            │       │       │           ├── flags: variable_call
            │       │       │           └── name: "b"
            │       │       └── closing_loc: (11...12) = "}"
            │       └── closing_loc: ∅
            ├── opening_loc: (0...3) = "%I["
            └── closing_loc: (12...13) = "]"
