@ ProgramNode (location: (0...53))
├── locals: [:a]
└── statements:
    @ StatementsNode (location: (0...53))
    └── body: (length: 4)
        ├── @ ClassVariableOperatorWriteNode (location: (0...11))
        │   ├── name: :@@var
        │   ├── name_loc: (0...5) = "@@var"
        │   ├── operator_loc: (6...8) = "|="
        │   ├── value:
        │   │   @ IntegerNode (location: (9...11))
        │   │   └── flags: decimal
        │   └── operator: :|
        ├── @ InstanceVariableOperatorWriteNode (location: (13...20))
        │   ├── name: :@a
        │   ├── name_loc: (13...15) = "@a"
        │   ├── operator_loc: (16...18) = "|="
        │   ├── value:
        │   │   @ IntegerNode (location: (19...20))
        │   │   └── flags: decimal
        │   └── operator: :|
        ├── @ LocalVariableOperatorWriteNode (location: (22...28))
        │   ├── name_loc: (22...23) = "a"
        │   ├── operator_loc: (24...26) = "+="
        │   ├── value:
        │   │   @ IntegerNode (location: (27...28))
        │   │   └── flags: decimal
        │   ├── name: :a
        │   ├── operator: :+
        │   └── depth: 0
        └── @ DefNode (location: (30...53))
            ├── name: :a
            ├── name_loc: (34...35) = "a"
            ├── receiver: ∅
            ├── parameters: ∅
            ├── body:
            │   @ StatementsNode (location: (37...48))
            │   └── body: (length: 1)
            │       └── @ ClassVariableOperatorWriteNode (location: (37...48))
            │           ├── name: :@@var
            │           ├── name_loc: (37...42) = "@@var"
            │           ├── operator_loc: (43...45) = "|="
            │           ├── value:
            │           │   @ IntegerNode (location: (46...48))
            │           │   └── flags: decimal
            │           └── operator: :|
            ├── locals: []
            ├── def_keyword_loc: (30...33) = "def"
            ├── operator_loc: ∅
            ├── lparen_loc: ∅
            ├── rparen_loc: ∅
            ├── equal_loc: ∅
            └── end_keyword_loc: (50...53) = "end"
