@ ProgramNode (location: (1,0)-(1,22))
├── locals: []
└── statements:
    @ StatementsNode (location: (1,0)-(1,22))
    └── body: (length: 1)
        └── @ CallNode (location: (1,0)-(1,22))
            ├── flags: ignore_visibility
            ├── receiver: ∅
            ├── call_operator_loc: ∅
            ├── name: :f
            ├── message_loc: (1,0)-(1,1) = "f"
            ├── opening_loc: ∅
            ├── arguments: ∅
            ├── closing_loc: ∅
            └── block:
                @ BlockNode (location: (1,2)-(1,22))
                ├── locals: [:a, :b, :c, :d]
                ├── parameters:
                │   @ BlockParametersNode (location: (1,4)-(1,20))
                │   ├── parameters:
                │   │   @ ParametersNode (location: (1,5)-(1,19))
                │   │   ├── requireds: (length: 2)
                │   │   │   ├── @ MultiTargetNode (location: (1,5)-(1,16))
                │   │   │   │   ├── lefts: (length: 2)
                │   │   │   │   │   ├── @ MultiTargetNode (location: (1,6)-(1,12))
                │   │   │   │   │   │   ├── lefts: (length: 2)
                │   │   │   │   │   │   │   ├── @ RequiredParameterNode (location: (1,7)-(1,8))
                │   │   │   │   │   │   │   │   ├── flags: ∅
                │   │   │   │   │   │   │   │   └── name: :a
                │   │   │   │   │   │   │   └── @ RequiredParameterNode (location: (1,10)-(1,11))
                │   │   │   │   │   │   │       ├── flags: ∅
                │   │   │   │   │   │   │       └── name: :b
                │   │   │   │   │   │   ├── rest: ∅
                │   │   │   │   │   │   ├── rights: (length: 0)
                │   │   │   │   │   │   ├── lparen_loc: (1,6)-(1,7) = "("
                │   │   │   │   │   │   └── rparen_loc: (1,11)-(1,12) = ")"
                │   │   │   │   │   └── @ RequiredParameterNode (location: (1,14)-(1,15))
                │   │   │   │   │       ├── flags: ∅
                │   │   │   │   │       └── name: :c
                │   │   │   │   ├── rest: ∅
                │   │   │   │   ├── rights: (length: 0)
                │   │   │   │   ├── lparen_loc: (1,5)-(1,6) = "("
                │   │   │   │   └── rparen_loc: (1,15)-(1,16) = ")"
                │   │   │   └── @ RequiredParameterNode (location: (1,18)-(1,19))
                │   │   │       ├── flags: ∅
                │   │   │       └── name: :d
                │   │   ├── optionals: (length: 0)
                │   │   ├── rest: ∅
                │   │   ├── posts: (length: 0)
                │   │   ├── keywords: (length: 0)
                │   │   ├── keyword_rest: ∅
                │   │   └── block: ∅
                │   ├── locals: (length: 0)
                │   ├── opening_loc: (1,4)-(1,5) = "|"
                │   └── closing_loc: (1,19)-(1,20) = "|"
                ├── body: ∅
                ├── opening_loc: (1,2)-(1,3) = "{"
                └── closing_loc: (1,21)-(1,22) = "}"