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