@ ProgramNode (location: (0...18))
├── locals: []
└── statements:
    @ StatementsNode (location: (0...18))
    └── body: (length: 1)
        └── @ CallNode (location: (0...18))
            ├── receiver:
            │   @ CallNode (location: (0...1))
            │   ├── receiver: ∅
            │   ├── call_operator_loc: ∅
            │   ├── message_loc: (0...1) = "a"
            │   ├── opening_loc: ∅
            │   ├── arguments: ∅
            │   ├── closing_loc: ∅
            │   ├── block: ∅
            │   ├── flags: variable_call
            │   └── name: "a"
            ├── call_operator_loc: (1...2) = "."
            ├── message_loc: (2...3) = "b"
            ├── opening_loc: ∅
            ├── arguments: ∅
            ├── closing_loc: ∅
            ├── block:
            │   @ BlockNode (location: (4...18))
            │   ├── locals: [:c]
            │   ├── parameters:
            │   │   @ BlockParametersNode (location: (7...14))
            │   │   ├── parameters: ∅
            │   │   ├── locals: (length: 1)
            │   │   │   └── @ BlockLocalVariableNode (location: (11...12))
            │   │   │       └── name: :c
            │   │   ├── opening_loc: (7...8) = "|"
            │   │   └── closing_loc: (13...14) = "|"
            │   ├── body: ∅
            │   ├── opening_loc: (4...6) = "do"
            │   └── closing_loc: (15...18) = "end"
            ├── flags: ∅
            └── name: "b"
