@ ProgramNode (location: (1,0)-(5,11))
├── locals: []
└── statements:
    @ StatementsNode (location: (1,0)-(5,11))
    └── body: (length: 3)
        ├── @ CallOperatorWriteNode (location: (1,0)-(1,10))
        │   ├── flags: ∅
        │   ├── receiver:
        │   │   @ CallNode (location: (1,0)-(1,3))
        │   │   ├── flags: variable_call
        │   │   ├── receiver: ∅
        │   │   ├── call_operator_loc: ∅
        │   │   ├── name: :foo
        │   │   ├── message_loc: (1,0)-(1,3) = "foo"
        │   │   ├── opening_loc: ∅
        │   │   ├── arguments: ∅
        │   │   ├── closing_loc: ∅
        │   │   └── block: ∅
        │   ├── call_operator_loc: (1,3)-(1,4) = "."
        │   ├── message_loc: (1,4)-(1,5) = "A"
        │   ├── read_name: :A
        │   ├── write_name: :A=
        │   ├── operator: :+
        │   ├── operator_loc: (1,6)-(1,8) = "+="
        │   └── value:
        │       @ IntegerNode (location: (1,9)-(1,10))
        │       └── flags: decimal
        ├── @ CallOperatorWriteNode (location: (3,0)-(3,10))
        │   ├── flags: ∅
        │   ├── receiver:
        │   │   @ CallNode (location: (3,0)-(3,3))
        │   │   ├── flags: variable_call
        │   │   ├── receiver: ∅
        │   │   ├── call_operator_loc: ∅
        │   │   ├── name: :foo
        │   │   ├── message_loc: (3,0)-(3,3) = "foo"
        │   │   ├── opening_loc: ∅
        │   │   ├── arguments: ∅
        │   │   ├── closing_loc: ∅
        │   │   └── block: ∅
        │   ├── call_operator_loc: (3,3)-(3,4) = "."
        │   ├── message_loc: (3,4)-(3,5) = "a"
        │   ├── read_name: :a
        │   ├── write_name: :a=
        │   ├── operator: :+
        │   ├── operator_loc: (3,6)-(3,8) = "+="
        │   └── value:
        │       @ IntegerNode (location: (3,9)-(3,10))
        │       └── flags: decimal
        └── @ CallOperatorWriteNode (location: (5,0)-(5,11))
            ├── flags: ∅
            ├── receiver:
            │   @ CallNode (location: (5,0)-(5,3))
            │   ├── flags: variable_call
            │   ├── receiver: ∅
            │   ├── call_operator_loc: ∅
            │   ├── name: :foo
            │   ├── message_loc: (5,0)-(5,3) = "foo"
            │   ├── opening_loc: ∅
            │   ├── arguments: ∅
            │   ├── closing_loc: ∅
            │   └── block: ∅
            ├── call_operator_loc: (5,3)-(5,5) = "::"
            ├── message_loc: (5,5)-(5,6) = "a"
            ├── read_name: :a
            ├── write_name: :a=
            ├── operator: :+
            ├── operator_loc: (5,7)-(5,9) = "+="
            └── value:
                @ IntegerNode (location: (5,10)-(5,11))
                └── flags: decimal
