@ ProgramNode (location: (1,0)-(1,14))
├── locals: []
└── statements:
    @ StatementsNode (location: (1,0)-(1,14))
    └── body: (length: 1)
        └── @ CallNode (location: (1,0)-(1,14))
            ├── flags: ignore_visibility
            ├── receiver: ∅
            ├── call_operator_loc: ∅
            ├── name: :m
            ├── message_loc: (1,0)-(1,1) = "m"
            ├── opening_loc: ∅
            ├── arguments:
            │   @ ArgumentsNode (location: (1,2)-(1,7))
            │   ├── flags: ∅
            │   └── arguments: (length: 1)
            │       └── @ CallNode (location: (1,2)-(1,7))
            │           ├── flags: ∅
            │           ├── receiver:
            │           │   @ CallNode (location: (1,2)-(1,3))
            │           │   ├── flags: variable_call, ignore_visibility
            │           │   ├── receiver: ∅
            │           │   ├── call_operator_loc: ∅
            │           │   ├── name: :a
            │           │   ├── message_loc: (1,2)-(1,3) = "a"
            │           │   ├── opening_loc: ∅
            │           │   ├── arguments: ∅
            │           │   ├── closing_loc: ∅
            │           │   └── block: ∅
            │           ├── call_operator_loc: ∅
            │           ├── name: :+
            │           ├── message_loc: (1,4)-(1,5) = "+"
            │           ├── opening_loc: ∅
            │           ├── arguments:
            │           │   @ ArgumentsNode (location: (1,6)-(1,7))
            │           │   ├── flags: ∅
            │           │   └── arguments: (length: 1)
            │           │       └── @ CallNode (location: (1,6)-(1,7))
            │           │           ├── flags: variable_call, ignore_visibility
            │           │           ├── receiver: ∅
            │           │           ├── call_operator_loc: ∅
            │           │           ├── name: :b
            │           │           ├── message_loc: (1,6)-(1,7) = "b"
            │           │           ├── opening_loc: ∅
            │           │           ├── arguments: ∅
            │           │           ├── closing_loc: ∅
            │           │           └── block: ∅
            │           ├── closing_loc: ∅
            │           └── block: ∅
            ├── closing_loc: ∅
            └── block:
                @ BlockNode (location: (1,8)-(1,14))
                ├── locals: []
                ├── parameters: ∅
                ├── body: ∅
                ├── opening_loc: (1,8)-(1,10) = "do"
                └── closing_loc: (1,11)-(1,14) = "end"