@ ProgramNode (location: (1,0)-(1,20))
├── locals: []
└── statements:
    @ StatementsNode (location: (1,0)-(1,20))
    └── body: (length: 1)
        └── @ ClassNode (location: (1,0)-(1,20))
            ├── locals: []
            ├── class_keyword_loc: (1,0)-(1,5) = "class"
            ├── constant_path:
            │   @ ConstantReadNode (location: (1,6)-(1,9))
            │   └── name: :Foo
            ├── inheritance_operator_loc: (1,10)-(1,11) = "<"
            ├── superclass:
            │   @ CallNode (location: (1,12)-(1,15))
            │   ├── flags: ignore_visibility
            │   ├── receiver: ∅
            │   ├── call_operator_loc: ∅
            │   ├── name: :a
            │   ├── message_loc: (1,12)-(1,13) = "a"
            │   ├── opening_loc: ∅
            │   ├── arguments:
            │   │   @ ArgumentsNode (location: (1,13)-(1,15))
            │   │   ├── flags: ∅
            │   │   └── arguments: (length: 1)
            │   │       └── @ SymbolNode (location: (1,13)-(1,15))
            │   │           ├── flags: forced_us_ascii_encoding
            │   │           ├── opening_loc: (1,13)-(1,14) = ":"
            │   │           ├── value_loc: (1,14)-(1,15) = "b"
            │   │           ├── closing_loc: ∅
            │   │           └── unescaped: "b"
            │   ├── closing_loc: ∅
            │   └── block: ∅
            ├── body: ∅
            ├── end_keyword_loc: (1,17)-(1,20) = "end"
            └── name: :Foo
