@ ProgramNode (location: (1,0)-(1,3))
├── flags: ∅
├── locals: []
└── statements:
    @ StatementsNode (location: (1,0)-(1,3))
    ├── flags: ∅
    └── body: (length: 1)
        └── @ CallNode (location: (1,0)-(1,3))
            ├── flags: newline, variable_call, ignore_visibility
            ├── receiver: ∅
            ├── call_operator_loc: ∅
            ├── name: :foo
            ├── message_loc: (1,0)-(1,3) = "foo"
            ├── opening_loc: ∅
            ├── arguments: ∅
            ├── closing_loc: ∅
            ├── equal_loc: ∅
            └── block: ∅
