@ ProgramNode (location: (0...12))
├── locals: []
└── statements:
    @ StatementsNode (location: (0...12))
    └── body: (length: 1)
        └── @ IfNode (location: (0...12))
            ├── if_keyword_loc: (0...2) = "if"
            ├── predicate:
            │   @ CallNode (location: (3...7))
            │   ├── receiver: ∅
            │   ├── call_operator_loc: ∅
            │   ├── message_loc: (3...4) = "f"
            │   ├── opening_loc: ∅
            │   ├── arguments:
            │   │   @ ArgumentsNode (location: (5...7))
            │   │   └── arguments: (length: 1)
            │   │       └── @ SymbolNode (location: (5...7))
            │   │           ├── opening_loc: (5...6) = ":"
            │   │           ├── value_loc: (6...7) = "x"
            │   │           ├── closing_loc: ∅
            │   │           └── unescaped: "x"
            │   ├── closing_loc: ∅
            │   ├── block: ∅
            │   ├── flags: ∅
            │   └── name: "f"
            ├── statements: ∅
            ├── consequent: ∅
            └── end_keyword_loc: (9...12) = "end"
