@ ProgramNode (location: (0...13))
├── locals: []
└── statements:
    @ StatementsNode (location: (0...13))
    └── body: (length: 1)
        └── @ PreExecutionNode (location: (0...13))
            ├── statements:
            │   @ StatementsNode (location: (8...11))
            │   └── body: (length: 1)
            │       └── @ CallNode (location: (8...11))
            │           ├── receiver: ∅
            │           ├── call_operator_loc: ∅
            │           ├── message_loc: (8...11) = "foo"
            │           ├── opening_loc: ∅
            │           ├── arguments: ∅
            │           ├── closing_loc: ∅
            │           ├── block: ∅
            │           ├── flags: variable_call
            │           └── name: "foo"
            ├── keyword_loc: (0...5) = "BEGIN"
            ├── opening_loc: (6...7) = "{"
            └── closing_loc: (12...13) = "}"
