@ ProgramNode (location: (1,0)-(4,3))
├── locals: []
└── statements:
    @ StatementsNode (location: (1,0)-(4,3))
    └── body: (length: 2)
        ├── @ CallNode (location: (1,0)-(1,3))
        │   ├── flags: ignore_visibility
        │   ├── receiver: ∅
        │   ├── call_operator_loc: ∅
        │   ├── name: :a
        │   ├── message_loc: (1,0)-(1,1) = "a"
        │   ├── opening_loc: ∅
        │   ├── arguments:
        │   │   @ ArgumentsNode (location: (1,2)-(1,3))
        │   │   ├── flags: ∅
        │   │   └── arguments: (length: 1)
        │   │       └── @ IntegerNode (location: (1,2)-(1,3))
        │   │           └── flags: decimal
        │   ├── closing_loc: ∅
        │   └── block: ∅
        └── @ CallNode (location: (2,0)-(4,3))
            ├── flags: ∅
            ├── receiver:
            │   @ CallNode (location: (2,0)-(2,1))
            │   ├── flags: variable_call, ignore_visibility
            │   ├── receiver: ∅
            │   ├── call_operator_loc: ∅
            │   ├── name: :a
            │   ├── message_loc: (2,0)-(2,1) = "a"
            │   ├── opening_loc: ∅
            │   ├── arguments: ∅
            │   ├── closing_loc: ∅
            │   └── block: ∅
            ├── call_operator_loc: (2,1)-(2,2) = "."
            ├── name: :b
            ├── message_loc: (2,2)-(2,3) = "b"
            ├── opening_loc: ∅
            ├── arguments: ∅
            ├── closing_loc: ∅
            └── block:
                @ BlockNode (location: (2,4)-(4,3))
                ├── locals: [:c]
                ├── parameters:
                │   @ BlockParametersNode (location: (2,7)-(2,10))
                │   ├── parameters:
                │   │   @ ParametersNode (location: (2,8)-(2,9))
                │   │   ├── requireds: (length: 1)
                │   │   │   └── @ RequiredParameterNode (location: (2,8)-(2,9))
                │   │   │       ├── flags: ∅
                │   │   │       └── name: :c
                │   │   ├── optionals: (length: 0)
                │   │   ├── rest: ∅
                │   │   ├── posts: (length: 0)
                │   │   ├── keywords: (length: 0)
                │   │   ├── keyword_rest: ∅
                │   │   └── block: ∅
                │   ├── locals: (length: 0)
                │   ├── opening_loc: (2,7)-(2,8) = "|"
                │   └── closing_loc: (2,9)-(2,10) = "|"
                ├── body: ∅
                ├── opening_loc: (2,4)-(2,6) = "do"
                └── closing_loc: (4,0)-(4,3) = "end"
