@ ProgramNode (location: (0...26))
├── locals: []
└── statements:
    @ StatementsNode (location: (0...26))
    └── body: (length: 1)
        └── @ CaseNode (location: (0...26))
            ├── predicate: ∅
            ├── conditions: (length: 1)
            │   └── @ WhenNode (location: (6...21))
            │       ├── keyword_loc: (6...10) = "when"
            │       ├── conditions: (length: 1)
            │       │   └── @ CallNode (location: (11...14))
            │       │       ├── receiver: ∅
            │       │       ├── call_operator_loc: ∅
            │       │       ├── message_loc: (11...14) = "foo"
            │       │       ├── opening_loc: ∅
            │       │       ├── arguments: ∅
            │       │       ├── closing_loc: ∅
            │       │       ├── block: ∅
            │       │       ├── flags: variable_call
            │       │       └── name: "foo"
            │       └── statements:
            │           @ StatementsNode (location: (16...21))
            │           └── body: (length: 1)
            │               └── @ StringNode (location: (16...21))
            │                   ├── opening_loc: (16...17) = "'"
            │                   ├── content_loc: (17...20) = "foo"
            │                   ├── closing_loc: (20...21) = "'"
            │                   └── unescaped: "foo"
            ├── consequent: ∅
            ├── case_keyword_loc: (0...4) = "case"
            └── end_keyword_loc: (23...26) = "end"
