@ ProgramNode (location: (1,0)-(9,17))
├── locals: []
└── statements:
    @ StatementsNode (location: (1,0)-(9,17))
    └── body: (length: 5)
        ├── @ CallNode (location: (1,0)-(1,2))
        │   ├── flags: variable_call
        │   ├── receiver: ∅
        │   ├── call_operator_loc: ∅
        │   ├── name: :_1
        │   ├── message_loc: (1,0)-(1,2) = "_1"
        │   ├── opening_loc: ∅
        │   ├── arguments: ∅
        │   ├── closing_loc: ∅
        │   └── block: ∅
        ├── @ SingletonClassNode (location: (3,0)-(3,21))
        │   ├── locals: []
        │   ├── class_keyword_loc: (3,0)-(3,5) = "class"
        │   ├── operator_loc: (3,6)-(3,8) = "<<"
        │   ├── expression:
        │   │   @ CallNode (location: (3,9)-(3,12))
        │   │   ├── flags: variable_call
        │   │   ├── receiver: ∅
        │   │   ├── call_operator_loc: ∅
        │   │   ├── name: :foo
        │   │   ├── message_loc: (3,9)-(3,12) = "foo"
        │   │   ├── opening_loc: ∅
        │   │   ├── arguments: ∅
        │   │   ├── closing_loc: ∅
        │   │   └── block: ∅
        │   ├── body:
        │   │   @ StatementsNode (location: (3,14)-(3,16))
        │   │   └── body: (length: 1)
        │   │       └── @ CallNode (location: (3,14)-(3,16))
        │   │           ├── flags: variable_call
        │   │           ├── receiver: ∅
        │   │           ├── call_operator_loc: ∅
        │   │           ├── name: :_1
        │   │           ├── message_loc: (3,14)-(3,16) = "_1"
        │   │           ├── opening_loc: ∅
        │   │           ├── arguments: ∅
        │   │           ├── closing_loc: ∅
        │   │           └── block: ∅
        │   └── end_keyword_loc: (3,18)-(3,21) = "end"
        ├── @ ClassNode (location: (5,0)-(5,16))
        │   ├── locals: []
        │   ├── class_keyword_loc: (5,0)-(5,5) = "class"
        │   ├── constant_path:
        │   │   @ ConstantReadNode (location: (5,6)-(5,7))
        │   │   └── name: :A
        │   ├── inheritance_operator_loc: ∅
        │   ├── superclass: ∅
        │   ├── body:
        │   │   @ StatementsNode (location: (5,9)-(5,11))
        │   │   └── body: (length: 1)
        │   │       └── @ CallNode (location: (5,9)-(5,11))
        │   │           ├── flags: variable_call
        │   │           ├── receiver: ∅
        │   │           ├── call_operator_loc: ∅
        │   │           ├── name: :_1
        │   │           ├── message_loc: (5,9)-(5,11) = "_1"
        │   │           ├── opening_loc: ∅
        │   │           ├── arguments: ∅
        │   │           ├── closing_loc: ∅
        │   │           └── block: ∅
        │   ├── end_keyword_loc: (5,13)-(5,16) = "end"
        │   └── name: :A
        ├── @ DefNode (location: (7,0)-(7,19))
        │   ├── name: :m
        │   ├── name_loc: (7,9)-(7,10) = "m"
        │   ├── receiver:
        │   │   @ SelfNode (location: (7,4)-(7,8))
        │   ├── parameters: ∅
        │   ├── body:
        │   │   @ StatementsNode (location: (7,12)-(7,14))
        │   │   └── body: (length: 1)
        │   │       └── @ CallNode (location: (7,12)-(7,14))
        │   │           ├── flags: variable_call
        │   │           ├── receiver: ∅
        │   │           ├── call_operator_loc: ∅
        │   │           ├── name: :_1
        │   │           ├── message_loc: (7,12)-(7,14) = "_1"
        │   │           ├── opening_loc: ∅
        │   │           ├── arguments: ∅
        │   │           ├── closing_loc: ∅
        │   │           └── block: ∅
        │   ├── locals: []
        │   ├── locals_body_index: 0
        │   ├── def_keyword_loc: (7,0)-(7,3) = "def"
        │   ├── operator_loc: (7,8)-(7,9) = "."
        │   ├── lparen_loc: ∅
        │   ├── rparen_loc: ∅
        │   ├── equal_loc: ∅
        │   └── end_keyword_loc: (7,16)-(7,19) = "end"
        └── @ ModuleNode (location: (9,0)-(9,17))
            ├── locals: []
            ├── module_keyword_loc: (9,0)-(9,6) = "module"
            ├── constant_path:
            │   @ ConstantReadNode (location: (9,7)-(9,8))
            │   └── name: :A
            ├── body:
            │   @ StatementsNode (location: (9,10)-(9,12))
            │   └── body: (length: 1)
            │       └── @ CallNode (location: (9,10)-(9,12))
            │           ├── flags: variable_call
            │           ├── receiver: ∅
            │           ├── call_operator_loc: ∅
            │           ├── name: :_1
            │           ├── message_loc: (9,10)-(9,12) = "_1"
            │           ├── opening_loc: ∅
            │           ├── arguments: ∅
            │           ├── closing_loc: ∅
            │           └── block: ∅
            ├── end_keyword_loc: (9,14)-(9,17) = "end"
            └── name: :A
