@ ProgramNode (location: (0...33))
├── locals: []
└── statements:
    @ StatementsNode (location: (0...33))
    └── body: (length: 1)
        └── @ CallNode (location: (0...33))
            ├── receiver: ∅
            ├── call_operator_loc: ∅
            ├── message_loc: (0...3) = "bar"
            ├── opening_loc: ∅
            ├── arguments:
            │   @ ArgumentsNode (location: (4...33))
            │   └── arguments: (length: 1)
            │       └── @ DefNode (location: (4...33))
            │           ├── name: :foo
            │           ├── name_loc: (8...11) = "foo"
            │           ├── receiver: ∅
            │           ├── parameters: ∅
            │           ├── body:
            │           │   @ StatementsNode (location: (13...29))
            │           │   └── body: (length: 1)
            │           │       └── @ CallNode (location: (13...29))
            │           │           ├── receiver:
            │           │           │   @ SelfNode (location: (13...17))
            │           │           ├── call_operator_loc: (17...18) = "."
            │           │           ├── message_loc: (18...22) = "each"
            │           │           ├── opening_loc: ∅
            │           │           ├── arguments: ∅
            │           │           ├── closing_loc: ∅
            │           │           ├── block:
            │           │           │   @ BlockNode (location: (23...29))
            │           │           │   ├── locals: []
            │           │           │   ├── parameters: ∅
            │           │           │   ├── body: ∅
            │           │           │   ├── opening_loc: (23...25) = "do"
            │           │           │   └── closing_loc: (26...29) = "end"
            │           │           ├── flags: ∅
            │           │           └── name: "each"
            │           ├── locals: []
            │           ├── def_keyword_loc: (4...7) = "def"
            │           ├── operator_loc: ∅
            │           ├── lparen_loc: ∅
            │           ├── rparen_loc: ∅
            │           ├── equal_loc: ∅
            │           └── end_keyword_loc: (30...33) = "end"
            ├── closing_loc: ∅
            ├── block: ∅
            ├── flags: ∅
            └── name: "bar"
