@ ProgramNode (location: (1,0)-(1,24))
├── locals: []
└── statements:
    @ StatementsNode (location: (1,0)-(1,24))
    └── body: (length: 1)
        └── @ CallNode (location: (1,0)-(1,24))
            ├── flags: ignore_visibility
            ├── receiver: ∅
            ├── call_operator_loc: ∅
            ├── name: :p
            ├── message_loc: (1,0)-(1,1) = "p"
            ├── opening_loc: ∅
            ├── arguments:
            │   @ ArgumentsNode (location: (1,2)-(1,24))
            │   ├── flags: ∅
            │   └── arguments: (length: 1)
            │       └── @ LambdaNode (location: (1,2)-(1,24))
            │           ├── locals: []
            │           ├── operator_loc: (1,2)-(1,4) = "->"
            │           ├── opening_loc: (1,7)-(1,9) = "do"
            │           ├── closing_loc: (1,21)-(1,24) = "end"
            │           ├── parameters:
            │           │   @ BlockParametersNode (location: (1,4)-(1,6))
            │           │   ├── parameters: ∅
            │           │   ├── locals: (length: 0)
            │           │   ├── opening_loc: (1,4)-(1,5) = "("
            │           │   └── closing_loc: (1,5)-(1,6) = ")"
            │           └── body:
            │               @ StatementsNode (location: (1,10)-(1,20))
            │               └── body: (length: 1)
            │                   └── @ CallNode (location: (1,10)-(1,20))
            │                       ├── flags: ignore_visibility
            │                       ├── receiver: ∅
            │                       ├── call_operator_loc: ∅
            │                       ├── name: :a
            │                       ├── message_loc: (1,10)-(1,11) = "a"
            │                       ├── opening_loc: (1,11)-(1,12) = "("
            │                       ├── arguments: ∅
            │                       ├── closing_loc: (1,12)-(1,13) = ")"
            │                       └── block:
            │                           @ BlockNode (location: (1,14)-(1,20))
            │                           ├── locals: []
            │                           ├── parameters: ∅
            │                           ├── body: ∅
            │                           ├── opening_loc: (1,14)-(1,16) = "do"
            │                           └── closing_loc: (1,17)-(1,20) = "end"
            ├── closing_loc: ∅
            └── block: ∅