@ ProgramNode (location: (1,0)-(1,13))
├── locals: []
└── statements:
    @ StatementsNode (location: (1,0)-(1,13))
    └── body: (length: 1)
        └── @ CallNode (location: (1,0)-(1,13))
            ├── flags: ignore_visibility
            ├── receiver: ∅
            ├── call_operator_loc: ∅
            ├── name: :lambda
            ├── message_loc: (1,0)-(1,6) = "lambda"
            ├── opening_loc: ∅
            ├── arguments: ∅
            ├── closing_loc: ∅
            └── block:
                @ BlockNode (location: (1,6)-(1,13))
                ├── locals: [:a]
                ├── parameters:
                │   @ BlockParametersNode (location: (1,7)-(1,11))
                │   ├── parameters: ∅
                │   ├── locals: (length: 1)
                │   │   └── @ BlockLocalVariableNode (location: (1,9)-(1,10))
                │   │       ├── flags: ∅
                │   │       └── name: :a
                │   ├── opening_loc: (1,7)-(1,8) = "|"
                │   └── closing_loc: (1,10)-(1,11) = "|"
                ├── body:
                │   @ StatementsNode (location: (1,11)-(1,12))
                │   └── body: (length: 1)
                │       └── @ LocalVariableReadNode (location: (1,11)-(1,12))
                │           ├── name: :a
                │           └── depth: 0
                ├── opening_loc: (1,6)-(1,7) = "{"
                └── closing_loc: (1,12)-(1,13) = "}"