@ ProgramNode (location: (1,0)-(15,12))
├── locals: [:_a]
└── statements:
    @ StatementsNode (location: (1,0)-(15,12))
    └── body: (length: 8)
        ├── @ IfNode (location: (1,0)-(1,9))
        │   ├── if_keyword_loc: ∅
        │   ├── predicate:
        │   │   @ CallNode (location: (1,0)-(1,1))
        │   │   ├── receiver: ∅
        │   │   ├── call_operator_loc: ∅
        │   │   ├── message_loc: (1,0)-(1,1) = "a"
        │   │   ├── opening_loc: ∅
        │   │   ├── arguments: ∅
        │   │   ├── closing_loc: ∅
        │   │   ├── block: ∅
        │   │   ├── flags: variable_call
        │   │   └── name: :a
        │   ├── statements:
        │   │   @ StatementsNode (location: (1,4)-(1,5))
        │   │   └── body: (length: 1)
        │   │       └── @ CallNode (location: (1,4)-(1,5))
        │   │           ├── receiver: ∅
        │   │           ├── call_operator_loc: ∅
        │   │           ├── message_loc: (1,4)-(1,5) = "b"
        │   │           ├── opening_loc: ∅
        │   │           ├── arguments: ∅
        │   │           ├── closing_loc: ∅
        │   │           ├── block: ∅
        │   │           ├── flags: variable_call
        │   │           └── name: :b
        │   ├── consequent:
        │   │   @ ElseNode (location: (1,6)-(1,9))
        │   │   ├── else_keyword_loc: (1,6)-(1,7) = ":"
        │   │   ├── statements:
        │   │   │   @ StatementsNode (location: (1,8)-(1,9))
        │   │   │   └── body: (length: 1)
        │   │   │       └── @ CallNode (location: (1,8)-(1,9))
        │   │   │           ├── receiver: ∅
        │   │   │           ├── call_operator_loc: ∅
        │   │   │           ├── message_loc: (1,8)-(1,9) = "c"
        │   │   │           ├── opening_loc: ∅
        │   │   │           ├── arguments: ∅
        │   │   │           ├── closing_loc: ∅
        │   │   │           ├── block: ∅
        │   │   │           ├── flags: variable_call
        │   │   │           └── name: :c
        │   │   └── end_keyword_loc: ∅
        │   └── end_keyword_loc: ∅
        ├── @ IfNode (location: (3,0)-(3,27))
        │   ├── if_keyword_loc: ∅
        │   ├── predicate:
        │   │   @ CallNode (location: (3,0)-(3,1))
        │   │   ├── receiver: ∅
        │   │   ├── call_operator_loc: ∅
        │   │   ├── message_loc: (3,0)-(3,1) = "a"
        │   │   ├── opening_loc: ∅
        │   │   ├── arguments: ∅
        │   │   ├── closing_loc: ∅
        │   │   ├── block: ∅
        │   │   ├── flags: variable_call
        │   │   └── name: :a
        │   ├── statements:
        │   │   @ StatementsNode (location: (3,4)-(3,14))
        │   │   └── body: (length: 1)
        │   │       └── @ DefinedNode (location: (3,4)-(3,14))
        │   │           ├── lparen_loc: ∅
        │   │           ├── value:
        │   │           │   @ CallNode (location: (3,13)-(3,14))
        │   │           │   ├── receiver: ∅
        │   │           │   ├── call_operator_loc: ∅
        │   │           │   ├── message_loc: (3,13)-(3,14) = "b"
        │   │           │   ├── opening_loc: ∅
        │   │           │   ├── arguments: ∅
        │   │           │   ├── closing_loc: ∅
        │   │           │   ├── block: ∅
        │   │           │   ├── flags: variable_call
        │   │           │   └── name: :b
        │   │           ├── rparen_loc: ∅
        │   │           └── keyword_loc: (3,4)-(3,12) = "defined?"
        │   ├── consequent:
        │   │   @ ElseNode (location: (3,15)-(3,27))
        │   │   ├── else_keyword_loc: (3,15)-(3,16) = ":"
        │   │   ├── statements:
        │   │   │   @ StatementsNode (location: (3,17)-(3,27))
        │   │   │   └── body: (length: 1)
        │   │   │       └── @ DefinedNode (location: (3,17)-(3,27))
        │   │   │           ├── lparen_loc: ∅
        │   │   │           ├── value:
        │   │   │           │   @ CallNode (location: (3,26)-(3,27))
        │   │   │           │   ├── receiver: ∅
        │   │   │           │   ├── call_operator_loc: ∅
        │   │   │           │   ├── message_loc: (3,26)-(3,27) = "c"
        │   │   │           │   ├── opening_loc: ∅
        │   │   │           │   ├── arguments: ∅
        │   │   │           │   ├── closing_loc: ∅
        │   │   │           │   ├── block: ∅
        │   │   │           │   ├── flags: variable_call
        │   │   │           │   └── name: :c
        │   │   │           ├── rparen_loc: ∅
        │   │   │           └── keyword_loc: (3,17)-(3,25) = "defined?"
        │   │   └── end_keyword_loc: ∅
        │   └── end_keyword_loc: ∅
        ├── @ IfNode (location: (5,0)-(5,15))
        │   ├── if_keyword_loc: ∅
        │   ├── predicate:
        │   │   @ CallNode (location: (5,0)-(5,6))
        │   │   ├── receiver: ∅
        │   │   ├── call_operator_loc: ∅
        │   │   ├── message_loc: (5,0)-(5,6) = "empty?"
        │   │   ├── opening_loc: ∅
        │   │   ├── arguments: ∅
        │   │   ├── closing_loc: ∅
        │   │   ├── block: ∅
        │   │   ├── flags: ∅
        │   │   └── name: :empty?
        │   ├── statements:
        │   │   @ StatementsNode (location: (5,7)-(5,11))
        │   │   └── body: (length: 1)
        │   │       └── @ TrueNode (location: (5,7)-(5,11))
        │   ├── consequent:
        │   │   @ ElseNode (location: (5,11)-(5,15))
        │   │   ├── else_keyword_loc: (5,11)-(5,12) = ":"
        │   │   ├── statements:
        │   │   │   @ StatementsNode (location: (5,12)-(5,15))
        │   │   │   └── body: (length: 1)
        │   │   │       └── @ NilNode (location: (5,12)-(5,15))
        │   │   └── end_keyword_loc: ∅
        │   └── end_keyword_loc: ∅
        ├── @ IfNode (location: (7,0)-(7,16))
        │   ├── if_keyword_loc: ∅
        │   ├── predicate:
        │   │   @ CallNode (location: (7,0)-(7,6))
        │   │   ├── receiver: ∅
        │   │   ├── call_operator_loc: ∅
        │   │   ├── message_loc: (7,0)-(7,6) = "empty?"
        │   │   ├── opening_loc: ∅
        │   │   ├── arguments: ∅
        │   │   ├── closing_loc: ∅
        │   │   ├── block: ∅
        │   │   ├── flags: ∅
        │   │   └── name: :empty?
        │   ├── statements:
        │   │   @ StatementsNode (location: (7,7)-(7,12))
        │   │   └── body: (length: 1)
        │   │       └── @ FalseNode (location: (7,7)-(7,12))
        │   ├── consequent:
        │   │   @ ElseNode (location: (7,12)-(7,16))
        │   │   ├── else_keyword_loc: (7,12)-(7,13) = ":"
        │   │   ├── statements:
        │   │   │   @ StatementsNode (location: (7,13)-(7,16))
        │   │   │   └── body: (length: 1)
        │   │   │       └── @ NilNode (location: (7,13)-(7,16))
        │   │   └── end_keyword_loc: ∅
        │   └── end_keyword_loc: ∅
        ├── @ IfNode (location: (9,0)-(9,14))
        │   ├── if_keyword_loc: ∅
        │   ├── predicate:
        │   │   @ CallNode (location: (9,0)-(9,6))
        │   │   ├── receiver: ∅
        │   │   ├── call_operator_loc: ∅
        │   │   ├── message_loc: (9,0)-(9,6) = "empty?"
        │   │   ├── opening_loc: ∅
        │   │   ├── arguments: ∅
        │   │   ├── closing_loc: ∅
        │   │   ├── block: ∅
        │   │   ├── flags: ∅
        │   │   └── name: :empty?
        │   ├── statements:
        │   │   @ StatementsNode (location: (9,7)-(9,10))
        │   │   └── body: (length: 1)
        │   │       └── @ NilNode (location: (9,7)-(9,10))
        │   ├── consequent:
        │   │   @ ElseNode (location: (9,10)-(9,14))
        │   │   ├── else_keyword_loc: (9,10)-(9,11) = ":"
        │   │   ├── statements:
        │   │   │   @ StatementsNode (location: (9,11)-(9,14))
        │   │   │   └── body: (length: 1)
        │   │   │       └── @ NilNode (location: (9,11)-(9,14))
        │   │   └── end_keyword_loc: ∅
        │   └── end_keyword_loc: ∅
        ├── @ IfNode (location: (11,0)-(11,10))
        │   ├── if_keyword_loc: ∅
        │   ├── predicate:
        │   │   @ CallNode (location: (11,0)-(11,2))
        │   │   ├── receiver: ∅
        │   │   ├── call_operator_loc: ∅
        │   │   ├── message_loc: (11,0)-(11,2) = "a?"
        │   │   ├── opening_loc: ∅
        │   │   ├── arguments: ∅
        │   │   ├── closing_loc: ∅
        │   │   ├── block: ∅
        │   │   ├── flags: ∅
        │   │   └── name: :a?
        │   ├── statements:
        │   │   @ StatementsNode (location: (11,3)-(11,6))
        │   │   └── body: (length: 1)
        │   │       └── @ NilNode (location: (11,3)-(11,6))
        │   ├── consequent:
        │   │   @ ElseNode (location: (11,6)-(11,10))
        │   │   ├── else_keyword_loc: (11,6)-(11,7) = ":"
        │   │   ├── statements:
        │   │   │   @ StatementsNode (location: (11,7)-(11,10))
        │   │   │   └── body: (length: 1)
        │   │   │       └── @ NilNode (location: (11,7)-(11,10))
        │   │   └── end_keyword_loc: ∅
        │   └── end_keyword_loc: ∅
        ├── @ IfNode (location: (13,0)-(13,14))
        │   ├── if_keyword_loc: ∅
        │   ├── predicate:
        │   │   @ CallNode (location: (13,0)-(13,1))
        │   │   ├── receiver: ∅
        │   │   ├── call_operator_loc: ∅
        │   │   ├── message_loc: (13,0)-(13,1) = "a"
        │   │   ├── opening_loc: ∅
        │   │   ├── arguments: ∅
        │   │   ├── closing_loc: ∅
        │   │   ├── block: ∅
        │   │   ├── flags: variable_call
        │   │   └── name: :a
        │   ├── statements:
        │   │   @ StatementsNode (location: (13,3)-(13,7))
        │   │   └── body: (length: 1)
        │   │       └── @ CallNode (location: (13,3)-(13,7))
        │   │           ├── receiver: ∅
        │   │           ├── call_operator_loc: ∅
        │   │           ├── message_loc: (13,3)-(13,7) = "var1"
        │   │           ├── opening_loc: ∅
        │   │           ├── arguments: ∅
        │   │           ├── closing_loc: ∅
        │   │           ├── block: ∅
        │   │           ├── flags: variable_call
        │   │           └── name: :var1
        │   ├── consequent:
        │   │   @ ElseNode (location: (13,8)-(13,14))
        │   │   ├── else_keyword_loc: (13,8)-(13,9) = ":"
        │   │   ├── statements:
        │   │   │   @ StatementsNode (location: (13,10)-(13,14))
        │   │   │   └── body: (length: 1)
        │   │   │       └── @ CallNode (location: (13,10)-(13,14))
        │   │   │           ├── receiver: ∅
        │   │   │           ├── call_operator_loc: ∅
        │   │   │           ├── message_loc: (13,10)-(13,14) = "var2"
        │   │   │           ├── opening_loc: ∅
        │   │   │           ├── arguments: ∅
        │   │   │           ├── closing_loc: ∅
        │   │   │           ├── block: ∅
        │   │   │           ├── flags: variable_call
        │   │   │           └── name: :var2
        │   │   └── end_keyword_loc: ∅
        │   └── end_keyword_loc: ∅
        └── @ IfNode (location: (15,0)-(15,12))
            ├── if_keyword_loc: ∅
            ├── predicate:
            │   @ CallNode (location: (15,0)-(15,4))
            │   ├── receiver: ∅
            │   ├── call_operator_loc: ∅
            │   ├── message_loc: (15,0)-(15,4) = "nil?"
            │   ├── opening_loc: ∅
            │   ├── arguments: ∅
            │   ├── closing_loc: ∅
            │   ├── block: ∅
            │   ├── flags: ∅
            │   └── name: :nil?
            ├── statements:
            │   @ StatementsNode (location: (15,5)-(15,10))
            │   └── body: (length: 1)
            │       └── @ LocalVariableWriteNode (location: (15,5)-(15,10))
            │           ├── name: :_a
            │           ├── depth: 0
            │           ├── name_loc: (15,5)-(15,7) = "_a"
            │           ├── value:
            │           │   @ IntegerNode (location: (15,9)-(15,10))
            │           │   └── flags: decimal
            │           └── operator_loc: (15,8)-(15,9) = "="
            ├── consequent:
            │   @ ElseNode (location: (15,10)-(15,12))
            │   ├── else_keyword_loc: (15,10)-(15,11) = ":"
            │   ├── statements:
            │   │   @ StatementsNode (location: (15,11)-(15,12))
            │   │   └── body: (length: 1)
            │   │       └── @ IntegerNode (location: (15,11)-(15,12))
            │   │           └── flags: decimal
            │   └── end_keyword_loc: ∅
            └── end_keyword_loc: ∅
