@ ProgramNode (location: (1,0)-(1,18))
├── locals: [:a]
└── statements:
    @ StatementsNode (location: (1,0)-(1,18))
    └── body: (length: 1)
        └── @ LocalVariableOrWriteNode (location: (1,0)-(1,18))
            ├── name_loc: (1,0)-(1,1) = "a"
            ├── operator_loc: (1,2)-(1,5) = "||="
            ├── value:
            │   @ RescueModifierNode (location: (1,6)-(1,18))
            │   ├── expression:
            │   │   @ CallNode (location: (1,6)-(1,7))
            │   │   ├── flags: variable_call, ignore_visibility
            │   │   ├── receiver: ∅
            │   │   ├── call_operator_loc: ∅
            │   │   ├── name: :b
            │   │   ├── message_loc: (1,6)-(1,7) = "b"
            │   │   ├── opening_loc: ∅
            │   │   ├── arguments: ∅
            │   │   ├── closing_loc: ∅
            │   │   └── block: ∅
            │   ├── keyword_loc: (1,8)-(1,14) = "rescue"
            │   └── rescue_expression:
            │       @ NilNode (location: (1,15)-(1,18))
            ├── name: :a
            └── depth: 0