@ ProgramNode (location: (1,0)-(3,15))
├── locals: []
└── statements:
    @ StatementsNode (location: (1,0)-(3,15))
    └── body: (length: 2)
        ├── @ CallOrWriteNode (location: (1,0)-(1,11))
        │   ├── flags: ∅
        │   ├── receiver:
        │   │   @ CallNode (location: (1,0)-(1,3))
        │   │   ├── flags: variable_call
        │   │   ├── receiver: ∅
        │   │   ├── call_operator_loc: ∅
        │   │   ├── name: :foo
        │   │   ├── message_loc: (1,0)-(1,3) = "foo"
        │   │   ├── opening_loc: ∅
        │   │   ├── arguments: ∅
        │   │   ├── closing_loc: ∅
        │   │   └── block: ∅
        │   ├── call_operator_loc: (1,3)-(1,4) = "."
        │   ├── message_loc: (1,4)-(1,5) = "a"
        │   ├── read_name: :a
        │   ├── write_name: :a=
        │   ├── operator_loc: (1,6)-(1,9) = "||="
        │   └── value:
        │       @ IntegerNode (location: (1,10)-(1,11))
        │       └── flags: decimal
        └── @ IndexOrWriteNode (location: (3,0)-(3,15))
            ├── flags: ∅
            ├── receiver:
            │   @ CallNode (location: (3,0)-(3,3))
            │   ├── flags: variable_call
            │   ├── receiver: ∅
            │   ├── call_operator_loc: ∅
            │   ├── name: :foo
            │   ├── message_loc: (3,0)-(3,3) = "foo"
            │   ├── opening_loc: ∅
            │   ├── arguments: ∅
            │   ├── closing_loc: ∅
            │   └── block: ∅
            ├── call_operator_loc: ∅
            ├── opening_loc: (3,3)-(3,4) = "["
            ├── arguments:
            │   @ ArgumentsNode (location: (3,4)-(3,8))
            │   ├── flags: ∅
            │   └── arguments: (length: 2)
            │       ├── @ IntegerNode (location: (3,4)-(3,5))
            │       │   └── flags: decimal
            │       └── @ IntegerNode (location: (3,7)-(3,8))
            │           └── flags: decimal
            ├── closing_loc: (3,8)-(3,9) = "]"
            ├── block: ∅
            ├── operator_loc: (3,10)-(3,13) = "||="
            └── value:
                @ IntegerNode (location: (3,14)-(3,15))
                └── flags: decimal
