@ ProgramNode (location: (1,0)-(1,4))
├── locals: []
└── statements:
    @ StatementsNode (location: (1,0)-(1,4))
    └── body: (length: 1)
        └── @ CallNode (location: (1,0)-(1,4))
            ├── flags: ignore_visibility
            ├── receiver: ∅
            ├── call_operator_loc: ∅
            ├── name: :foo!
            ├── message_loc: (1,0)-(1,4) = "foo!"
            ├── opening_loc: ∅
            ├── arguments: ∅
            ├── closing_loc: ∅
            └── block: ∅