@ ProgramNode (location: (0...35))
├── locals: []
└── statements:
    @ StatementsNode (location: (0...35))
    └── body: (length: 3)
        ├── @ CallOperatorWriteNode (location: (0...10))
        │   ├── 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: (3...4) = "."
        │   ├── message_loc: (4...5) = "A"
        │   ├── opening_loc: ∅
        │   ├── arguments: ∅
        │   ├── closing_loc: ∅
        │   ├── flags: ∅
        │   ├── read_name: "A"
        │   ├── write_name: "A="
        │   ├── operator: :+
        │   ├── operator_loc: (6...8) = "+="
        │   └── value:
        │       @ IntegerNode (location: (9...10))
        │       └── flags: decimal
        ├── @ CallOperatorWriteNode (location: (12...22))
        │   ├── receiver:
        │   │   @ CallNode (location: (12...15))
        │   │   ├── receiver: ∅
        │   │   ├── call_operator_loc: ∅
        │   │   ├── message_loc: (12...15) = "foo"
        │   │   ├── opening_loc: ∅
        │   │   ├── arguments: ∅
        │   │   ├── closing_loc: ∅
        │   │   ├── block: ∅
        │   │   ├── flags: variable_call
        │   │   └── name: "foo"
        │   ├── call_operator_loc: (15...16) = "."
        │   ├── message_loc: (16...17) = "a"
        │   ├── opening_loc: ∅
        │   ├── arguments: ∅
        │   ├── closing_loc: ∅
        │   ├── flags: ∅
        │   ├── read_name: "a"
        │   ├── write_name: "a="
        │   ├── operator: :+
        │   ├── operator_loc: (18...20) = "+="
        │   └── value:
        │       @ IntegerNode (location: (21...22))
        │       └── flags: decimal
        └── @ CallOperatorWriteNode (location: (24...35))
            ├── receiver:
            │   @ CallNode (location: (24...27))
            │   ├── receiver: ∅
            │   ├── call_operator_loc: ∅
            │   ├── message_loc: (24...27) = "foo"
            │   ├── opening_loc: ∅
            │   ├── arguments: ∅
            │   ├── closing_loc: ∅
            │   ├── block: ∅
            │   ├── flags: variable_call
            │   └── name: "foo"
            ├── call_operator_loc: (27...29) = "::"
            ├── message_loc: (29...30) = "a"
            ├── opening_loc: ∅
            ├── arguments: ∅
            ├── closing_loc: ∅
            ├── flags: ∅
            ├── read_name: "a"
            ├── write_name: "a="
            ├── operator: :+
            ├── operator_loc: (31...33) = "+="
            └── value:
                @ IntegerNode (location: (34...35))
                └── flags: decimal
