@ ProgramNode (location: (1,0)-(1,6))
├── locals: []
└── statements:
    @ StatementsNode (location: (1,0)-(1,6))
    └── body: (length: 1)
        └── @ CallNode (location: (1,0)-(1,6))
            ├── flags: ∅
            ├── receiver:
            │   @ IntegerNode (location: (1,4)-(1,6))
            │   ├── flags: decimal
            │   └── value: 42
            ├── call_operator_loc: ∅
            ├── name: :!
            ├── message_loc: (1,0)-(1,3) = "not"
            ├── opening_loc: ∅
            ├── arguments: ∅
            ├── closing_loc: ∅
            └── block: ∅