@ ProgramNode (location: (1,0)-(5,3))
├── locals: []
└── statements:
    @ StatementsNode (location: (1,0)-(5,3))
    └── body: (length: 1)
        └── @ DefNode (location: (1,0)-(5,3))
            ├── name: :x
            ├── name_loc: (1,4)-(1,5) = "x"
            ├── receiver: ∅
            ├── parameters:
            │   @ ParametersNode (location: (1,6)-(1,7))
            │   ├── requireds: (length: 1)
            │   │   └── @ RequiredParameterNode (location: (1,6)-(1,7))
            │   │       └── name: :y
            │   ├── optionals: (length: 0)
            │   ├── rest: ∅
            │   ├── posts: (length: 0)
            │   ├── keywords: (length: 0)
            │   ├── keyword_rest: ∅
            │   └── block: ∅
            ├── body:
            │   @ StatementsNode (location: (2,2)-(4,10))
            │   └── body: (length: 3)
            │       ├── @ CallNode (location: (2,2)-(2,6))
            │       │   ├── flags: ∅
            │       │   ├── receiver: ∅
            │       │   ├── call_operator_loc: ∅
            │       │   ├── name: :p
            │       │   ├── message_loc: (2,2)-(2,3) = "p"
            │       │   ├── opening_loc: (2,3)-(2,4) = "("
            │       │   ├── arguments:
            │       │   │   @ ArgumentsNode (location: (2,4)-(2,5))
            │       │   │   ├── flags: ∅
            │       │   │   └── arguments: (length: 1)
            │       │   │       └── @ LocalVariableReadNode (location: (2,4)-(2,5))
            │       │   │           ├── name: :y
            │       │   │           └── depth: 0
            │       │   ├── closing_loc: (2,5)-(2,6) = ")"
            │       │   └── block: ∅
            │       ├── @ LocalVariableOperatorWriteNode (location: (3,2)-(3,8))
            │       │   ├── name_loc: (3,2)-(3,3) = "y"
            │       │   ├── operator_loc: (3,4)-(3,6) = "*="
            │       │   ├── value:
            │       │   │   @ IntegerNode (location: (3,7)-(3,8))
            │       │   │   └── flags: decimal
            │       │   ├── name: :y
            │       │   ├── operator: :*
            │       │   └── depth: 0
            │       └── @ ReturnNode (location: (4,2)-(4,10))
            │           ├── keyword_loc: (4,2)-(4,8) = "return"
            │           └── arguments:
            │               @ ArgumentsNode (location: (4,9)-(4,10))
            │               ├── flags: ∅
            │               └── arguments: (length: 1)
            │                   └── @ LocalVariableReadNode (location: (4,9)-(4,10))
            │                       ├── name: :y
            │                       └── depth: 0
            ├── locals: [:y]
            ├── locals_body_index: 1
            ├── def_keyword_loc: (1,0)-(1,3) = "def"
            ├── operator_loc: ∅
            ├── lparen_loc: (1,5)-(1,6) = "("
            ├── rparen_loc: (1,7)-(1,8) = ")"
            ├── equal_loc: ∅
            └── end_keyword_loc: (5,0)-(5,3) = "end"
