@ ProgramNode (location: (1,0)-(1,10))
├── locals: []
└── statements:
    @ StatementsNode (location: (1,0)-(1,10))
    └── body: (length: 1)
        └── @ CallNode (location: (1,0)-(1,10))
            ├── flags: ignore_visibility
            ├── receiver: ∅
            ├── call_operator_loc: ∅
            ├── name: :a
            ├── message_loc: (1,0)-(1,1) = "a"
            ├── opening_loc: ∅
            ├── arguments: ∅
            ├── closing_loc: ∅
            └── block:
                @ BlockNode (location: (1,2)-(1,10))
                ├── locals: [:b]
                ├── parameters:
                │   @ BlockParametersNode (location: (1,4)-(1,8))
                │   ├── parameters: ∅
                │   ├── locals: (length: 1)
                │   │   └── @ BlockLocalVariableNode (location: (1,6)-(1,7))
                │   │       ├── flags: ∅
                │   │       └── name: :b
                │   ├── opening_loc: (1,4)-(1,5) = "|"
                │   └── closing_loc: (1,7)-(1,8) = "|"
                ├── body: ∅
                ├── opening_loc: (1,2)-(1,3) = "{"
                └── closing_loc: (1,9)-(1,10) = "}"