@ 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: :a
            ├── message_loc: (1,0)-(1,1) = "a"
            ├── opening_loc: ∅
            ├── arguments:
            │   @ ArgumentsNode (location: (1,2)-(1,13))
            │   ├── flags: ∅
            │   └── arguments: (length: 1)
            │       └── @ LambdaNode (location: (1,2)-(1,13))
            │           ├── locals: []
            │           ├── operator_loc: (1,2)-(1,4) = "->"
            │           ├── opening_loc: (1,5)-(1,7) = "do"
            │           ├── closing_loc: (1,10)-(1,13) = "end"
            │           ├── parameters: ∅
            │           └── body:
            │               @ StatementsNode (location: (1,8)-(1,9))
            │               └── body: (length: 1)
            │                   └── @ IntegerNode (location: (1,8)-(1,9))
            │                       └── flags: decimal
            ├── closing_loc: ∅
            └── block:
                @ BlockNode (location: (1,14)-(1,22))
                ├── locals: []
                ├── parameters: ∅
                ├── body:
                │   @ StatementsNode (location: (1,17)-(1,18))
                │   └── body: (length: 1)
                │       └── @ IntegerNode (location: (1,17)-(1,18))
                │           └── flags: decimal
                ├── opening_loc: (1,14)-(1,16) = "do"
                └── closing_loc: (1,19)-(1,22) = "end"
