@ ProgramNode (location: (0...42))
├── locals: []
└── statements:
    @ StatementsNode (location: (0...42))
    └── body: (length: 4)
        ├── @ CallNode (location: (0...10))
        │   ├── receiver: ∅
        │   ├── call_operator_loc: ∅
        │   ├── message_loc: (0...3) = "fun"
        │   ├── opening_loc: ∅
        │   ├── arguments: ∅
        │   ├── closing_loc: ∅
        │   ├── block:
        │   │   @ BlockNode (location: (4...10))
        │   │   ├── locals: []
        │   │   ├── parameters: ∅
        │   │   ├── body: ∅
        │   │   ├── opening_loc: (4...6) = "do"
        │   │   └── closing_loc: (7...10) = "end"
        │   ├── flags: ∅
        │   └── name: "fun"
        ├── @ CallNode (location: (12...19))
        │   ├── receiver: ∅
        │   ├── call_operator_loc: ∅
        │   ├── message_loc: (12...15) = "fun"
        │   ├── opening_loc: ∅
        │   ├── arguments: ∅
        │   ├── closing_loc: ∅
        │   ├── block:
        │   │   @ BlockNode (location: (16...19))
        │   │   ├── locals: []
        │   │   ├── parameters: ∅
        │   │   ├── body: ∅
        │   │   ├── opening_loc: (16...17) = "{"
        │   │   └── closing_loc: (18...19) = "}"
        │   ├── flags: ∅
        │   └── name: "fun"
        ├── @ CallNode (location: (21...30))
        │   ├── receiver: ∅
        │   ├── call_operator_loc: ∅
        │   ├── message_loc: (21...24) = "fun"
        │   ├── opening_loc: (24...25) = "("
        │   ├── arguments: ∅
        │   ├── closing_loc: (25...26) = ")"
        │   ├── block:
        │   │   @ BlockNode (location: (27...30))
        │   │   ├── locals: []
        │   │   ├── parameters: ∅
        │   │   ├── body: ∅
        │   │   ├── opening_loc: (27...28) = "{"
        │   │   └── closing_loc: (29...30) = "}"
        │   ├── flags: ∅
        │   └── name: "fun"
        └── @ CallNode (location: (32...42))
            ├── receiver: ∅
            ├── call_operator_loc: ∅
            ├── message_loc: (32...35) = "fun"
            ├── opening_loc: (35...36) = "("
            ├── arguments:
            │   @ ArgumentsNode (location: (36...37))
            │   └── arguments: (length: 1)
            │       └── @ IntegerNode (location: (36...37))
            │           └── flags: decimal
            ├── closing_loc: (37...38) = ")"
            ├── block:
            │   @ BlockNode (location: (39...42))
            │   ├── locals: []
            │   ├── parameters: ∅
            │   ├── body: ∅
            │   ├── opening_loc: (39...40) = "{"
            │   └── closing_loc: (41...42) = "}"
            ├── flags: ∅
            └── name: "fun"
