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