@ ProgramNode (location: (0...42))
├── locals: []
└── statements:
    @ StatementsNode (location: (0...42))
    └── body: (length: 2)
        ├── @ WhileNode (location: (0...21))
        │   ├── keyword_loc: (0...5) = "while"
        │   ├── closing_loc: (18...21) = "end"
        │   ├── predicate:
        │   │   @ CallNode (location: (6...9))
        │   │   ├── receiver: ∅
        │   │   ├── call_operator_loc: ∅
        │   │   ├── message_loc: (6...9) = "foo"
        │   │   ├── opening_loc: ∅
        │   │   ├── arguments: ∅
        │   │   ├── closing_loc: ∅
        │   │   ├── block: ∅
        │   │   ├── flags: variable_call
        │   │   └── name: "foo"
        │   ├── statements:
        │   │   @ StatementsNode (location: (13...17))
        │   │   └── body: (length: 1)
        │   │       └── @ CallNode (location: (13...17))
        │   │           ├── receiver: ∅
        │   │           ├── call_operator_loc: ∅
        │   │           ├── message_loc: (13...17) = "meth"
        │   │           ├── opening_loc: ∅
        │   │           ├── arguments: ∅
        │   │           ├── closing_loc: ∅
        │   │           ├── block: ∅
        │   │           ├── flags: variable_call
        │   │           └── name: "meth"
        │   └── flags: ∅
        └── @ WhileNode (location: (23...42))
            ├── keyword_loc: (23...28) = "while"
            ├── closing_loc: (39...42) = "end"
            ├── predicate:
            │   @ CallNode (location: (29...32))
            │   ├── receiver: ∅
            │   ├── call_operator_loc: ∅
            │   ├── message_loc: (29...32) = "foo"
            │   ├── opening_loc: ∅
            │   ├── arguments: ∅
            │   ├── closing_loc: ∅
            │   ├── block: ∅
            │   ├── flags: variable_call
            │   └── name: "foo"
            ├── statements:
            │   @ StatementsNode (location: (34...38))
            │   └── body: (length: 1)
            │       └── @ CallNode (location: (34...38))
            │           ├── receiver: ∅
            │           ├── call_operator_loc: ∅
            │           ├── message_loc: (34...38) = "meth"
            │           ├── opening_loc: ∅
            │           ├── arguments: ∅
            │           ├── closing_loc: ∅
            │           ├── block: ∅
            │           ├── flags: variable_call
            │           └── name: "meth"
            └── flags: ∅
