@ ProgramNode (location: (1,0)-(1,25))
├── locals: []
└── statements:
    @ StatementsNode (location: (1,0)-(1,25))
    └── body: (length: 1)
        └── @ IndexOperatorWriteNode (location: (1,0)-(1,25))
            ├── flags: ∅
            ├── receiver:
            │   @ CallNode (location: (1,0)-(1,1))
            │   ├── flags: variable_call, ignore_visibility
            │   ├── receiver: ∅
            │   ├── call_operator_loc: ∅
            │   ├── name: :y
            │   ├── message_loc: (1,0)-(1,1) = "y"
            │   ├── opening_loc: ∅
            │   ├── arguments: ∅
            │   ├── closing_loc: ∅
            │   └── block: ∅
            ├── call_operator_loc: ∅
            ├── opening_loc: (1,1)-(1,2) = "["
            ├── arguments:
            │   @ ArgumentsNode (location: (1,2)-(1,11))
            │   ├── flags: ∅
            │   └── arguments: (length: 1)
            │       └── @ InterpolatedStringNode (location: (1,2)-(1,11))
            │           ├── flags: ∅
            │           ├── opening_loc: (1,2)-(1,3) = "\""
            │           ├── parts: (length: 2)
            │           │   ├── @ EmbeddedStatementsNode (location: (1,3)-(1,8))
            │           │   │   ├── opening_loc: (1,3)-(1,5) = "\#{"
            │           │   │   ├── statements:
            │           │   │   │   @ StatementsNode (location: (1,5)-(1,7))
            │           │   │   │   └── body: (length: 1)
            │           │   │   │       └── @ IntegerNode (location: (1,5)-(1,7))
            │           │   │   │           ├── flags: decimal
            │           │   │   │           └── value: 42
            │           │   │   └── closing_loc: (1,7)-(1,8) = "}"
            │           │   └── @ StringNode (location: (1,8)-(1,10))
            │           │       ├── flags: frozen
            │           │       ├── opening_loc: ∅
            │           │       ├── content_loc: (1,8)-(1,10) = "\\n"
            │           │       ├── closing_loc: ∅
            │           │       └── unescaped: "\n"
            │           └── closing_loc: (1,10)-(1,11) = "\""
            ├── closing_loc: (1,11)-(1,12) = "]"
            ├── block: ∅
            ├── operator: :+
            ├── operator_loc: (1,13)-(1,15) = "+="
            └── value:
                @ InterpolatedStringNode (location: (1,16)-(1,25))
                ├── flags: ∅
                ├── opening_loc: (1,16)-(1,17) = "\""
                ├── parts: (length: 2)
                │   ├── @ EmbeddedStatementsNode (location: (1,17)-(1,22))
                │   │   ├── opening_loc: (1,17)-(1,19) = "\#{"
                │   │   ├── statements:
                │   │   │   @ StatementsNode (location: (1,19)-(1,21))
                │   │   │   └── body: (length: 1)
                │   │   │       └── @ IntegerNode (location: (1,19)-(1,21))
                │   │   │           ├── flags: decimal
                │   │   │           └── value: 42
                │   │   └── closing_loc: (1,21)-(1,22) = "}"
                │   └── @ StringNode (location: (1,22)-(1,24))
                │       ├── flags: frozen
                │       ├── opening_loc: ∅
                │       ├── content_loc: (1,22)-(1,24) = "\\n"
                │       ├── closing_loc: ∅
                │       └── unescaped: "\n"
                └── closing_loc: (1,24)-(1,25) = "\""