@ ProgramNode (location: (1,0)-(7,10))
├── locals: []
└── statements:
    @ StatementsNode (location: (1,0)-(7,10))
    └── body: (length: 4)
        ├── @ CallNode (location: (1,0)-(1,10))
        │   ├── receiver: ∅
        │   ├── call_operator_loc: ∅
        │   ├── message_loc: (1,0)-(1,3) = "fun"
        │   ├── opening_loc: ∅
        │   ├── arguments: ∅
        │   ├── closing_loc: ∅
        │   ├── block:
        │   │   @ BlockNode (location: (1,4)-(1,10))
        │   │   ├── locals: []
        │   │   ├── parameters: ∅
        │   │   ├── body: ∅
        │   │   ├── opening_loc: (1,4)-(1,6) = "do"
        │   │   └── closing_loc: (1,7)-(1,10) = "end"
        │   ├── flags: ∅
        │   └── name: :fun
        ├── @ CallNode (location: (3,0)-(3,7))
        │   ├── receiver: ∅
        │   ├── call_operator_loc: ∅
        │   ├── message_loc: (3,0)-(3,3) = "fun"
        │   ├── opening_loc: ∅
        │   ├── arguments: ∅
        │   ├── closing_loc: ∅
        │   ├── block:
        │   │   @ BlockNode (location: (3,4)-(3,7))
        │   │   ├── locals: []
        │   │   ├── parameters: ∅
        │   │   ├── body: ∅
        │   │   ├── opening_loc: (3,4)-(3,5) = "{"
        │   │   └── closing_loc: (3,6)-(3,7) = "}"
        │   ├── flags: ∅
        │   └── name: :fun
        ├── @ CallNode (location: (5,0)-(5,9))
        │   ├── receiver: ∅
        │   ├── call_operator_loc: ∅
        │   ├── message_loc: (5,0)-(5,3) = "fun"
        │   ├── opening_loc: (5,3)-(5,4) = "("
        │   ├── arguments: ∅
        │   ├── closing_loc: (5,4)-(5,5) = ")"
        │   ├── block:
        │   │   @ BlockNode (location: (5,6)-(5,9))
        │   │   ├── locals: []
        │   │   ├── parameters: ∅
        │   │   ├── body: ∅
        │   │   ├── opening_loc: (5,6)-(5,7) = "{"
        │   │   └── closing_loc: (5,8)-(5,9) = "}"
        │   ├── flags: ∅
        │   └── name: :fun
        └── @ CallNode (location: (7,0)-(7,10))
            ├── receiver: ∅
            ├── call_operator_loc: ∅
            ├── message_loc: (7,0)-(7,3) = "fun"
            ├── opening_loc: (7,3)-(7,4) = "("
            ├── arguments:
            │   @ ArgumentsNode (location: (7,4)-(7,5))
            │   ├── arguments: (length: 1)
            │   │   └── @ IntegerNode (location: (7,4)-(7,5))
            │   │       └── flags: decimal
            │   └── flags: ∅
            ├── closing_loc: (7,5)-(7,6) = ")"
            ├── block:
            │   @ BlockNode (location: (7,7)-(7,10))
            │   ├── locals: []
            │   ├── parameters: ∅
            │   ├── body: ∅
            │   ├── opening_loc: (7,7)-(7,8) = "{"
            │   └── closing_loc: (7,9)-(7,10) = "}"
            ├── flags: ∅
            └── name: :fun
