@ ProgramNode (location: (1,0)-(5,13))
├── locals: []
└── statements:
    @ StatementsNode (location: (1,0)-(5,13))
    └── body: (length: 3)
        ├── @ DefinedNode (location: (1,0)-(1,13))
        │   ├── lparen_loc: ∅
        │   ├── value:
        │   │   @ InstanceVariableReadNode (location: (1,9)-(1,13))
        │   │   └── name: :@foo
        │   ├── rparen_loc: ∅
        │   └── keyword_loc: (1,0)-(1,8) = "defined?"
        ├── @ DefinedNode (location: (3,0)-(3,12))
        │   ├── lparen_loc: ∅
        │   ├── value:
        │   │   @ CallNode (location: (3,9)-(3,12))
        │   │   ├── flags: variable_call, ignore_visibility
        │   │   ├── receiver: ∅
        │   │   ├── call_operator_loc: ∅
        │   │   ├── name: :foo
        │   │   ├── message_loc: (3,9)-(3,12) = "foo"
        │   │   ├── opening_loc: ∅
        │   │   ├── arguments: ∅
        │   │   ├── closing_loc: ∅
        │   │   └── block: ∅
        │   ├── rparen_loc: ∅
        │   └── keyword_loc: (3,0)-(3,8) = "defined?"
        └── @ DefinedNode (location: (5,0)-(5,13))
            ├── lparen_loc: (5,8)-(5,9) = "("
            ├── value:
            │   @ CallNode (location: (5,9)-(5,12))
            │   ├── flags: variable_call, ignore_visibility
            │   ├── receiver: ∅
            │   ├── call_operator_loc: ∅
            │   ├── name: :foo
            │   ├── message_loc: (5,9)-(5,12) = "foo"
            │   ├── opening_loc: ∅
            │   ├── arguments: ∅
            │   ├── closing_loc: ∅
            │   └── block: ∅
            ├── rparen_loc: (5,12)-(5,13) = ")"
            └── keyword_loc: (5,0)-(5,8) = "defined?"