@ ProgramNode (location: (1,0)-(1,25))
├── flags: ∅
├── locals: []
└── statements:
    @ StatementsNode (location: (1,0)-(1,25))
    ├── flags: ∅
    └── body: (length: 1)
        └── @ LambdaNode (location: (1,0)-(1,25))
            ├── flags: newline
            ├── locals: [:a, :b]
            ├── operator_loc: (1,0)-(1,2) = "->"
            ├── opening_loc: (1,13)-(1,14) = "{"
            ├── closing_loc: (1,24)-(1,25) = "}"
            ├── parameters:
            │   @ BlockParametersNode (location: (1,2)-(1,12))
            │   ├── flags: ∅
            │   ├── parameters:
            │   │   @ ParametersNode (location: (1,3)-(1,11))
            │   │   ├── flags: ∅
            │   │   ├── requireds: (length: 1)
            │   │   │   └── @ RequiredParameterNode (location: (1,3)-(1,4))
            │   │   │       ├── flags: ∅
            │   │   │       └── name: :a
            │   │   ├── optionals: (length: 1)
            │   │   │   └── @ OptionalParameterNode (location: (1,6)-(1,11))
            │   │   │       ├── flags: ∅
            │   │   │       ├── name: :b
            │   │   │       ├── name_loc: (1,6)-(1,7) = "b"
            │   │   │       ├── operator_loc: (1,7)-(1,8) = "="
            │   │   │       └── value:
            │   │   │           @ NilNode (location: (1,8)-(1,11))
            │   │   │           └── flags: static_literal
            │   │   ├── rest: ∅
            │   │   ├── posts: (length: 0)
            │   │   ├── keywords: (length: 0)
            │   │   ├── keyword_rest: ∅
            │   │   └── block: ∅
            │   ├── locals: (length: 0)
            │   ├── opening_loc: (1,2)-(1,3) = "("
            │   └── closing_loc: (1,11)-(1,12) = ")"
            └── body:
                @ StatementsNode (location: (1,15)-(1,23))
                ├── flags: ∅
                └── body: (length: 1)
                    └── @ CallNode (location: (1,15)-(1,23))
                        ├── flags: newline, ignore_visibility
                        ├── receiver: ∅
                        ├── call_operator_loc: ∅
                        ├── name: :p
                        ├── message_loc: (1,15)-(1,16) = "p"
                        ├── opening_loc: ∅
                        ├── arguments:
                        │   @ ArgumentsNode (location: (1,17)-(1,23))
                        │   ├── flags: ∅
                        │   └── arguments: (length: 1)
                        │       └── @ ArrayNode (location: (1,17)-(1,23))
                        │           ├── flags: ∅
                        │           ├── elements: (length: 2)
                        │           │   ├── @ LocalVariableReadNode (location: (1,18)-(1,19))
                        │           │   │   ├── flags: ∅
                        │           │   │   ├── name: :a
                        │           │   │   └── depth: 0
                        │           │   └── @ LocalVariableReadNode (location: (1,21)-(1,22))
                        │           │       ├── flags: ∅
                        │           │       ├── name: :b
                        │           │       └── depth: 0
                        │           ├── opening_loc: (1,17)-(1,18) = "["
                        │           └── closing_loc: (1,22)-(1,23) = "]"
                        ├── closing_loc: ∅
                        └── block: ∅
