@ ProgramNode (location: (1,0)-(1,10))
├── locals: []
└── statements:
    @ StatementsNode (location: (1,0)-(1,10))
    └── body: (length: 1)
        └── @ IfNode (location: (1,0)-(1,10))
            ├── if_keyword_loc: (1,0)-(1,2) = "if"
            ├── predicate:
            │   @ IntegerNode (location: (1,3)-(1,5))
            │   ├── flags: decimal
            │   └── value: -1
            ├── then_keyword_loc: ∅
            ├── statements: ∅
            ├── consequent: ∅
            └── end_keyword_loc: (1,7)-(1,10) = "end"