@ ProgramNode (location: (0...35))
├── locals: []
└── statements:
    @ StatementsNode (location: (0...35))
    └── body: (length: 1)
        └── @ CallNode (location: (0...35))
            ├── receiver: ∅
            ├── call_operator_loc: ∅
            ├── message_loc: (0...1) = "f"
            ├── opening_loc: ∅
            ├── arguments: ∅
            ├── closing_loc: ∅
            ├── block:
            │   @ BlockNode (location: (2...35))
            │   ├── locals: [:a, :b, :c]
            │   ├── parameters:
            │   │   @ BlockParametersNode (location: (4...23))
            │   │   ├── parameters:
            │   │   │   @ ParametersNode (location: (5...22))
            │   │   │   ├── requireds: (length: 1)
            │   │   │   │   └── @ RequiredParameterNode (location: (5...6))
            │   │   │   │       └── name: :a
            │   │   │   ├── optionals: (length: 2)
            │   │   │   │   ├── @ OptionalParameterNode (location: (8...14))
            │   │   │   │   │   ├── name: :b
            │   │   │   │   │   ├── name_loc: (8...9) = "b"
            │   │   │   │   │   ├── operator_loc: (10...11) = "="
            │   │   │   │   │   └── value:
            │   │   │   │   │       @ IntegerNode (location: (12...14))
            │   │   │   │   │       └── flags: decimal
            │   │   │   │   └── @ OptionalParameterNode (location: (16...22))
            │   │   │   │       ├── name: :c
            │   │   │   │       ├── name_loc: (16...17) = "c"
            │   │   │   │       ├── operator_loc: (18...19) = "="
            │   │   │   │       └── value:
            │   │   │   │           @ IntegerNode (location: (20...22))
            │   │   │   │           └── flags: decimal
            │   │   │   ├── rest: ∅
            │   │   │   ├── posts: (length: 0)
            │   │   │   ├── keywords: (length: 0)
            │   │   │   ├── keyword_rest: ∅
            │   │   │   └── block: ∅
            │   │   ├── locals: (length: 0)
            │   │   ├── opening_loc: (4...5) = "|"
            │   │   └── closing_loc: (22...23) = "|"
            │   ├── body:
            │   │   @ StatementsNode (location: (24...33))
            │   │   └── body: (length: 1)
            │   │       └── @ ArrayNode (location: (24...33))
            │   │           ├── elements: (length: 3)
            │   │           │   ├── @ LocalVariableReadNode (location: (25...26))
            │   │           │   │   ├── name: :a
            │   │           │   │   └── depth: 0
            │   │           │   ├── @ LocalVariableReadNode (location: (28...29))
            │   │           │   │   ├── name: :b
            │   │           │   │   └── depth: 0
            │   │           │   └── @ LocalVariableReadNode (location: (31...32))
            │   │           │       ├── name: :c
            │   │           │       └── depth: 0
            │   │           ├── opening_loc: (24...25) = "["
            │   │           └── closing_loc: (32...33) = "]"
            │   ├── opening_loc: (2...3) = "{"
            │   └── closing_loc: (34...35) = "}"
            ├── flags: ∅
            └── name: "f"
