@ ProgramNode (location: (1,0)-(2,10))
├── locals: []
└── statements:
    @ StatementsNode (location: (1,0)-(2,10))
    └── body: (length: 2)
        ├── @ CallNode (location: (1,0)-(1,5))
        │   ├── flags: ignore_visibility
        │   ├── receiver: ∅
        │   ├── call_operator_loc: ∅
        │   ├── name: :a
        │   ├── message_loc: (1,0)-(1,1) = "a"
        │   ├── opening_loc: ∅
        │   ├── arguments:
        │   │   @ ArgumentsNode (location: (1,2)-(1,5))
        │   │   ├── flags: ∅
        │   │   └── arguments: (length: 1)
        │   │       └── @ ParenthesesNode (location: (1,2)-(1,5))
        │   │           ├── body:
        │   │           │   @ StatementsNode (location: (1,3)-(1,4))
        │   │           │   └── body: (length: 1)
        │   │           │       └── @ CallNode (location: (1,3)-(1,4))
        │   │           │           ├── flags: variable_call, ignore_visibility
        │   │           │           ├── receiver: ∅
        │   │           │           ├── call_operator_loc: ∅
        │   │           │           ├── name: :b
        │   │           │           ├── message_loc: (1,3)-(1,4) = "b"
        │   │           │           ├── opening_loc: ∅
        │   │           │           ├── arguments: ∅
        │   │           │           ├── closing_loc: ∅
        │   │           │           └── block: ∅
        │   │           ├── opening_loc: (1,2)-(1,3) = "("
        │   │           └── closing_loc: (1,4)-(1,5) = ")"
        │   ├── closing_loc: ∅
        │   └── block: ∅
        └── @ CallNode (location: (2,0)-(2,10))
            ├── flags: ∅
            ├── receiver:
            │   @ CallNode (location: (2,0)-(2,1))
            │   ├── flags: variable_call, ignore_visibility
            │   ├── receiver: ∅
            │   ├── call_operator_loc: ∅
            │   ├── name: :c
            │   ├── message_loc: (2,0)-(2,1) = "c"
            │   ├── opening_loc: ∅
            │   ├── arguments: ∅
            │   ├── closing_loc: ∅
            │   └── block: ∅
            ├── call_operator_loc: (2,1)-(2,2) = "."
            ├── name: :d
            ├── message_loc: (2,2)-(2,3) = "d"
            ├── opening_loc: ∅
            ├── arguments: ∅
            ├── closing_loc: ∅
            └── block:
                @ BlockNode (location: (2,4)-(2,10))
                ├── locals: []
                ├── parameters: ∅
                ├── body: ∅
                ├── opening_loc: (2,4)-(2,6) = "do"
                └── closing_loc: (2,7)-(2,10) = "end"