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