@ ProgramNode (location: (0...41))
├── locals: []
└── statements:
    @ StatementsNode (location: (0...41))
    └── body: (length: 1)
        └── @ IfNode (location: (0...41))
            ├── if_keyword_loc: (0...2) = "if"
            ├── predicate:
            │   @ CallNode (location: (3...15))
            │   ├── receiver:
            │   │   @ CallNode (location: (7...15))
            │   │   ├── receiver:
            │   │   │   @ CallNode (location: (7...10))
            │   │   │   ├── receiver: ∅
            │   │   │   ├── call_operator_loc: ∅
            │   │   │   ├── message_loc: (7...10) = "var"
            │   │   │   ├── opening_loc: ∅
            │   │   │   ├── arguments: ∅
            │   │   │   ├── closing_loc: ∅
            │   │   │   ├── block: ∅
            │   │   │   ├── flags: variable_call
            │   │   │   └── name: "var"
            │   │   ├── call_operator_loc: (10...11) = "."
            │   │   ├── message_loc: (11...15) = "nil?"
            │   │   ├── opening_loc: ∅
            │   │   ├── arguments: ∅
            │   │   ├── closing_loc: ∅
            │   │   ├── block: ∅
            │   │   ├── flags: ∅
            │   │   └── name: "nil?"
            │   ├── call_operator_loc: ∅
            │   ├── message_loc: (3...6) = "not"
            │   ├── opening_loc: ∅
            │   ├── arguments: ∅
            │   ├── closing_loc: ∅
            │   ├── block: ∅
            │   ├── flags: ∅
            │   └── name: "!"
            ├── statements:
            │   @ StatementsNode (location: (21...26))
            │   └── body: (length: 1)
            │       └── @ StringNode (location: (21...26))
            │           ├── opening_loc: (21...22) = "'"
            │           ├── content_loc: (22...25) = "foo"
            │           ├── closing_loc: (25...26) = "'"
            │           └── unescaped: "foo"
            ├── consequent:
            │   @ ElseNode (location: (27...41))
            │   ├── else_keyword_loc: (27...31) = "else"
            │   ├── statements:
            │   │   @ StatementsNode (location: (32...37))
            │   │   └── body: (length: 1)
            │   │       └── @ StringNode (location: (32...37))
            │   │           ├── opening_loc: (32...33) = "'"
            │   │           ├── content_loc: (33...36) = "bar"
            │   │           ├── closing_loc: (36...37) = "'"
            │   │           └── unescaped: "bar"
            │   └── end_keyword_loc: (38...41) = "end"
            └── end_keyword_loc: (38...41) = "end"
