@ ProgramNode (location: (1,0)-(5,6))
├── locals: []
└── statements:
    @ StatementsNode (location: (1,0)-(5,6))
    └── body: (length: 3)
        ├── @ CallNode (location: (1,0)-(1,3))
        │   ├── flags: variable_call
        │   ├── receiver: ∅
        │   ├── call_operator_loc: ∅
        │   ├── name: :fun
        │   ├── message_loc: (1,0)-(1,3) = "fun"
        │   ├── opening_loc: ∅
        │   ├── arguments: ∅
        │   ├── closing_loc: ∅
        │   └── block: ∅
        ├── @ CallNode (location: (3,0)-(3,4))
        │   ├── flags: ∅
        │   ├── receiver: ∅
        │   ├── call_operator_loc: ∅
        │   ├── name: :fun!
        │   ├── message_loc: (3,0)-(3,4) = "fun!"
        │   ├── opening_loc: ∅
        │   ├── arguments: ∅
        │   ├── closing_loc: ∅
        │   └── block: ∅
        └── @ CallNode (location: (5,0)-(5,6))
            ├── flags: ∅
            ├── receiver: ∅
            ├── call_operator_loc: ∅
            ├── name: :fun
            ├── message_loc: (5,0)-(5,3) = "fun"
            ├── opening_loc: (5,3)-(5,4) = "("
            ├── arguments:
            │   @ ArgumentsNode (location: (5,4)-(5,5))
            │   ├── flags: ∅
            │   └── arguments: (length: 1)
            │       └── @ IntegerNode (location: (5,4)-(5,5))
            │           └── flags: decimal
            ├── closing_loc: (5,5)-(5,6) = ")"
            └── block: ∅
