@ ProgramNode (location: (0...13))
├── locals: [:a, :b]
└── statements:
    @ StatementsNode (location: (0...13))
    └── body: (length: 1)
        └── @ CallNode (location: (0...13))
            ├── receiver:
            │   @ ParenthesesNode (location: (1...13))
            │   ├── body:
            │   │   @ StatementsNode (location: (2...12))
            │   │   └── body: (length: 1)
            │   │       └── @ MultiWriteNode (location: (2...12))
            │   │           ├── targets: (length: 2)
            │   │           │   ├── @ LocalVariableTargetNode (location: (2...3))
            │   │           │   │   ├── name: :a
            │   │           │   │   └── depth: 0
            │   │           │   └── @ LocalVariableTargetNode (location: (5...6))
            │   │           │       ├── name: :b
            │   │           │       └── depth: 0
            │   │           ├── lparen_loc: ∅
            │   │           ├── rparen_loc: ∅
            │   │           ├── operator_loc: (7...8) = "="
            │   │           └── value:
            │   │               @ CallNode (location: (9...12))
            │   │               ├── receiver: ∅
            │   │               ├── call_operator_loc: ∅
            │   │               ├── message_loc: (9...12) = "foo"
            │   │               ├── opening_loc: ∅
            │   │               ├── arguments: ∅
            │   │               ├── closing_loc: ∅
            │   │               ├── block: ∅
            │   │               ├── flags: variable_call
            │   │               └── name: "foo"
            │   ├── opening_loc: (1...2) = "("
            │   └── closing_loc: (12...13) = ")"
            ├── call_operator_loc: ∅
            ├── message_loc: (0...1) = "!"
            ├── opening_loc: ∅
            ├── arguments: ∅
            ├── closing_loc: ∅
            ├── block: ∅
            ├── flags: ∅
            └── name: "!"
