@ ProgramNode (location: (1,0)-(1,15))
├── locals: []
└── statements:
    @ StatementsNode (location: (1,0)-(1,15))
    └── body: (length: 1)
        └── @ IfNode (location: (1,0)-(1,15))
            ├── if_keyword_loc: ∅
            ├── predicate:
            │   @ CallNode (location: (1,0)-(1,1))
            │   ├── flags: variable_call
            │   ├── receiver: ∅
            │   ├── call_operator_loc: ∅
            │   ├── name: :a
            │   ├── message_loc: (1,0)-(1,1) = "a"
            │   ├── opening_loc: ∅
            │   ├── arguments: ∅
            │   ├── closing_loc: ∅
            │   └── block: ∅
            ├── then_keyword_loc: (1,2)-(1,3) = "?"
            ├── statements:
            │   @ StatementsNode (location: (1,4)-(1,10))
            │   └── body: (length: 1)
            │       └── @ CallNode (location: (1,4)-(1,10))
            │           ├── flags: ∅
            │           ├── receiver:
            │           │   @ CallNode (location: (1,4)-(1,5))
            │           │   ├── flags: variable_call
            │           │   ├── receiver: ∅
            │           │   ├── call_operator_loc: ∅
            │           │   ├── name: :b
            │           │   ├── message_loc: (1,4)-(1,5) = "b"
            │           │   ├── opening_loc: ∅
            │           │   ├── arguments: ∅
            │           │   ├── closing_loc: ∅
            │           │   └── block: ∅
            │           ├── call_operator_loc: ∅
            │           ├── name: :&
            │           ├── message_loc: (1,6)-(1,7) = "&"
            │           ├── opening_loc: ∅
            │           ├── arguments:
            │           │   @ ArgumentsNode (location: (1,8)-(1,10))
            │           │   ├── flags: ∅
            │           │   └── arguments: (length: 1)
            │           │       └── @ StringNode (location: (1,8)-(1,10))
            │           │           ├── flags: ∅
            │           │           ├── opening_loc: (1,8)-(1,9) = "'"
            │           │           ├── content_loc: (1,9)-(1,9) = ""
            │           │           ├── closing_loc: (1,9)-(1,10) = "'"
            │           │           └── unescaped: ""
            │           ├── closing_loc: ∅
            │           └── block: ∅
            ├── consequent:
            │   @ ElseNode (location: (1,10)-(1,15))
            │   ├── else_keyword_loc: (1,10)-(1,11) = ":"
            │   ├── statements:
            │   │   @ StatementsNode (location: (1,12)-(1,15))
            │   │   └── body: (length: 1)
            │   │       └── @ NilNode (location: (1,12)-(1,15))
            │   └── end_keyword_loc: ∅
            └── end_keyword_loc: ∅
