@ ProgramNode (location: (0...16))
├── locals: []
└── statements:
    @ StatementsNode (location: (0...16))
    └── body: (length: 1)
        └── @ CallNode (location: (0...16))
            ├── receiver: ∅
            ├── call_operator_loc: ∅
            ├── message_loc: (0...1) = "f"
            ├── opening_loc: ∅
            ├── arguments: ∅
            ├── closing_loc: ∅
            ├── block:
            │   @ BlockNode (location: (2...16))
            │   ├── locals: [:a, :b]
            │   ├── parameters:
            │   │   @ BlockParametersNode (location: (4...12))
            │   │   ├── parameters:
            │   │   │   @ ParametersNode (location: (5...11))
            │   │   │   ├── requireds: (length: 1)
            │   │   │   │   └── @ RequiredDestructuredParameterNode (location: (5...11))
            │   │   │   │       ├── parameters: (length: 2)
            │   │   │   │       │   ├── @ RequiredParameterNode (location: (6...7))
            │   │   │   │       │   │   └── name: :a
            │   │   │   │       │   └── @ RequiredParameterNode (location: (9...10))
            │   │   │   │       │       └── name: :b
            │   │   │   │       ├── opening_loc: (5...6) = "("
            │   │   │   │       └── closing_loc: (10...11) = ")"
            │   │   │   ├── optionals: (length: 0)
            │   │   │   ├── rest: ∅
            │   │   │   ├── posts: (length: 0)
            │   │   │   ├── keywords: (length: 0)
            │   │   │   ├── keyword_rest: ∅
            │   │   │   └── block: ∅
            │   │   ├── locals: (length: 0)
            │   │   ├── opening_loc: (4...5) = "|"
            │   │   └── closing_loc: (11...12) = "|"
            │   ├── body:
            │   │   @ StatementsNode (location: (13...14))
            │   │   └── body: (length: 1)
            │   │       └── @ CallNode (location: (13...14))
            │   │           ├── receiver: ∅
            │   │           ├── call_operator_loc: ∅
            │   │           ├── message_loc: (13...14) = "d"
            │   │           ├── opening_loc: ∅
            │   │           ├── arguments: ∅
            │   │           ├── closing_loc: ∅
            │   │           ├── block: ∅
            │   │           ├── flags: variable_call
            │   │           └── name: "d"
            │   ├── opening_loc: (2...3) = "{"
            │   └── closing_loc: (15...16) = "}"
            ├── flags: ∅
            └── name: "f"
