@ ProgramNode (location: (0...15))
├── locals: []
└── statements:
    @ StatementsNode (location: (0...15))
    └── body: (length: 1)
        └── @ CallNode (location: (0...15))
            ├── receiver:
            │   @ CallNode (location: (0...3))
            │   ├── receiver: ∅
            │   ├── call_operator_loc: ∅
            │   ├── message_loc: (0...3) = "foo"
            │   ├── opening_loc: ∅
            │   ├── arguments: ∅
            │   ├── closing_loc: ∅
            │   ├── block: ∅
            │   ├── flags: variable_call
            │   └── name: "foo"
            ├── call_operator_loc: ∅
            ├── message_loc: (3...15) = "[:baz => 1,]"
            ├── opening_loc: (3...4) = "["
            ├── arguments:
            │   @ ArgumentsNode (location: (4...13))
            │   └── arguments: (length: 1)
            │       └── @ KeywordHashNode (location: (4...13))
            │           └── elements: (length: 1)
            │               └── @ AssocNode (location: (4...13))
            │                   ├── key:
            │                   │   @ SymbolNode (location: (4...8))
            │                   │   ├── opening_loc: (4...5) = ":"
            │                   │   ├── value_loc: (5...8) = "baz"
            │                   │   ├── closing_loc: ∅
            │                   │   └── unescaped: "baz"
            │                   ├── value:
            │                   │   @ IntegerNode (location: (12...13))
            │                   │   └── flags: decimal
            │                   └── operator_loc: (9...11) = "=>"
            ├── closing_loc: (14...15) = "]"
            ├── block: ∅
            ├── flags: ∅
            └── name: "[]"
