@ ProgramNode (location: (0...12))
├── locals: []
└── statements:
    @ StatementsNode (location: (0...12))
    └── body: (length: 2)
        ├── @ SymbolNode (location: (0...6))
        │   ├── opening_loc: (0...2) = ":'"
        │   ├── value_loc: (2...5) = "foo"
        │   ├── closing_loc: (5...6) = "'"
        │   └── unescaped: "foo"
        └── @ SymbolNode (location: (8...12))
            ├── opening_loc: (8...9) = ":"
            ├── value_loc: (9...12) = "foo"
            ├── closing_loc: ∅
            └── unescaped: "foo"
