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