@ ProgramNode (location: (1,0)-(1,14))
├── locals: []
└── statements:
    @ StatementsNode (location: (1,0)-(1,14))
    └── body: (length: 1)
        └── @ CallNode (location: (1,0)-(1,14))
            ├── flags: ∅
            ├── receiver:
            │   @ CallNode (location: (1,0)-(1,1))
            │   ├── flags: variable_call
            │   ├── receiver: ∅
            │   ├── call_operator_loc: ∅
            │   ├── name: :a
            │   ├── message_loc: (1,0)-(1,1) = "a"
            │   ├── opening_loc: ∅
            │   ├── arguments: ∅
            │   ├── closing_loc: ∅
            │   └── block: ∅
            ├── call_operator_loc: (1,1)-(1,2) = "."
            ├── name: :b
            ├── message_loc: (1,2)-(1,3) = "b"
            ├── opening_loc: ∅
            ├── arguments: ∅
            ├── closing_loc: ∅
            └── block:
                @ BlockNode (location: (1,4)-(1,14))
                ├── locals: []
                ├── locals_body_index: 0
                ├── parameters:
                │   @ BlockParametersNode (location: (1,7)-(1,10))
                │   ├── parameters: ∅
                │   ├── locals: (length: 0)
                │   ├── opening_loc: (1,7)-(1,8) = "|"
                │   └── closing_loc: (1,9)-(1,10) = "|"
                ├── body: ∅
                ├── opening_loc: (1,4)-(1,6) = "do"
                └── closing_loc: (1,11)-(1,14) = "end"
