@ ProgramNode (location: (0...25))
├── locals: []
└── statements:
    @ StatementsNode (location: (0...25))
    └── body: (length: 1)
        └── @ DefNode (location: (0...25))
            ├── name: :foo
            ├── name_loc: (4...7) = "foo"
            ├── receiver: ∅
            ├── parameters:
            │   @ ParametersNode (location: (8...10))
            │   ├── requireds: (length: 0)
            │   ├── optionals: (length: 0)
            │   ├── rest: ∅
            │   ├── posts: (length: 0)
            │   ├── keywords: (length: 0)
            │   ├── keyword_rest:
            │   │   @ KeywordRestParameterNode (location: (8...10))
            │   │   ├── name: nil
            │   │   ├── name_loc: ∅
            │   │   └── operator_loc: (8...10) = "**"
            │   └── block: ∅
            ├── body:
            │   @ StatementsNode (location: (13...20))
            │   └── body: (length: 1)
            │       └── @ CallNode (location: (13...20))
            │           ├── receiver: ∅
            │           ├── call_operator_loc: ∅
            │           ├── message_loc: (13...16) = "bar"
            │           ├── opening_loc: (16...17) = "("
            │           ├── arguments:
            │           │   @ ArgumentsNode (location: (17...19))
            │           │   └── arguments: (length: 1)
            │           │       └── @ KeywordHashNode (location: (17...19))
            │           │           └── elements: (length: 1)
            │           │               └── @ AssocSplatNode (location: (17...19))
            │           │                   ├── value: ∅
            │           │                   └── operator_loc: (17...19) = "**"
            │           ├── closing_loc: (19...20) = ")"
            │           ├── block: ∅
            │           ├── flags: ∅
            │           └── name: "bar"
            ├── locals: [:**]
            ├── def_keyword_loc: (0...3) = "def"
            ├── operator_loc: ∅
            ├── lparen_loc: (7...8) = "("
            ├── rparen_loc: (10...11) = ")"
            ├── equal_loc: ∅
            └── end_keyword_loc: (22...25) = "end"
