@ ProgramNode (location: (1,0)-(1,26))
├── locals: []
└── statements:
    @ StatementsNode (location: (1,0)-(1,26))
    └── body: (length: 1)
        └── @ DefNode (location: (1,0)-(1,26))
            ├── name: :fun
            ├── name_loc: (1,4)-(1,7) = "fun"
            ├── receiver: ∅
            ├── parameters:
            │   @ ParametersNode (location: (1,8)-(1,16))
            │   ├── requireds: (length: 0)
            │   ├── optionals: (length: 0)
            │   ├── rest: ∅
            │   ├── posts: (length: 0)
            │   ├── keywords: (length: 1)
            │   │   └── @ OptionalKeywordParameterNode (location: (1,8)-(1,16))
            │   │       ├── flags: ∅
            │   │       ├── name: :kw
            │   │       ├── name_loc: (1,8)-(1,11) = "kw:"
            │   │       └── value:
            │   │           @ SymbolNode (location: (1,12)-(1,16))
            │   │           ├── flags: forced_us_ascii_encoding
            │   │           ├── opening_loc: (1,12)-(1,13) = ":"
            │   │           ├── value_loc: (1,13)-(1,16) = "val"
            │   │           ├── closing_loc: ∅
            │   │           └── unescaped: "val"
            │   ├── keyword_rest: ∅
            │   └── block: ∅
            ├── body:
            │   @ StatementsNode (location: (1,19)-(1,21))
            │   └── body: (length: 1)
            │       └── @ LocalVariableReadNode (location: (1,19)-(1,21))
            │           ├── name: :kw
            │           └── depth: 0
            ├── locals: [:kw]
            ├── def_keyword_loc: (1,0)-(1,3) = "def"
            ├── operator_loc: ∅
            ├── lparen_loc: (1,7)-(1,8) = "("
            ├── rparen_loc: (1,16)-(1,17) = ")"
            ├── equal_loc: ∅
            └── end_keyword_loc: (1,23)-(1,26) = "end"
