@ ProgramNode (location: (0...9))
├── locals: []
└── statements:
    @ StatementsNode (location: (0...9))
    └── body: (length: 1)
        └── @ CallNode (location: (0...9))
            ├── receiver:
            │   @ CallNode (location: (0...3))
            │   ├── receiver: ∅
            │   ├── call_operator_loc: ∅
            │   ├── message_loc: (0...3) = "foo"
            │   ├── opening_loc: ∅
            │   ├── arguments: ∅
            │   ├── closing_loc: ∅
            │   ├── block: ∅
            │   ├── flags: variable_call
            │   └── name: "foo"
            ├── call_operator_loc: ∅
            ├── message_loc: (3...9) = "[bar,]"
            ├── opening_loc: (3...4) = "["
            ├── arguments:
            │   @ ArgumentsNode (location: (4...7))
            │   └── arguments: (length: 1)
            │       └── @ CallNode (location: (4...7))
            │           ├── receiver: ∅
            │           ├── call_operator_loc: ∅
            │           ├── message_loc: (4...7) = "bar"
            │           ├── opening_loc: ∅
            │           ├── arguments: ∅
            │           ├── closing_loc: ∅
            │           ├── block: ∅
            │           ├── flags: variable_call
            │           └── name: "bar"
            ├── closing_loc: (8...9) = "]"
            ├── block: ∅
            ├── flags: ∅
            └── name: "[]"
