@ ProgramNode (location: (1,0)-(1,20))
├── locals: []
└── statements:
    @ StatementsNode (location: (1,0)-(1,20))
    └── body: (length: 1)
        └── @ CallNode (location: (1,0)-(1,20))
            ├── receiver: ∅
            ├── call_operator_loc: ∅
            ├── message_loc: (1,0)-(1,3) = "foo"
            ├── opening_loc: (1,3)-(1,4) = "("
            ├── arguments:
            │   @ ArgumentsNode (location: (1,4)-(1,18))
            │   ├── arguments: (length: 2)
            │   │   ├── @ SymbolNode (location: (1,4)-(1,8))
            │   │   │   ├── opening_loc: (1,4)-(1,5) = ":"
            │   │   │   ├── value_loc: (1,5)-(1,8) = "bar"
            │   │   │   ├── closing_loc: ∅
            │   │   │   └── unescaped: "bar"
            │   │   └── @ KeywordHashNode (location: (1,10)-(1,18))
            │   │       └── elements: (length: 1)
            │   │           └── @ AssocNode (location: (1,10)-(1,18))
            │   │               ├── key:
            │   │               │   @ SymbolNode (location: (1,10)-(1,14))
            │   │               │   ├── opening_loc: ∅
            │   │               │   ├── value_loc: (1,10)-(1,13) = "baz"
            │   │               │   ├── closing_loc: (1,13)-(1,14) = ":"
            │   │               │   └── unescaped: "baz"
            │   │               ├── value:
            │   │               │   @ NilNode (location: (1,15)-(1,18))
            │   │               └── operator_loc: ∅
            │   └── flags: ∅
            ├── closing_loc: (1,19)-(1,20) = ")"
            ├── block: ∅
            ├── flags: ∅
            └── name: :foo
