@ ProgramNode (location: (1,0)-(3,22))
├── locals: [:a]
└── statements:
    @ StatementsNode (location: (1,0)-(3,22))
    └── body: (length: 2)
        ├── @ ForNode (location: (1,0)-(1,24))
        │   ├── index:
        │   │   @ LocalVariableTargetNode (location: (1,4)-(1,5))
        │   │   ├── name: :a
        │   │   └── depth: 0
        │   ├── collection:
        │   │   @ CallNode (location: (1,9)-(1,12))
        │   │   ├── flags: variable_call
        │   │   ├── receiver: ∅
        │   │   ├── call_operator_loc: ∅
        │   │   ├── name: :foo
        │   │   ├── message_loc: (1,9)-(1,12) = "foo"
        │   │   ├── opening_loc: ∅
        │   │   ├── arguments: ∅
        │   │   ├── closing_loc: ∅
        │   │   └── block: ∅
        │   ├── statements:
        │   │   @ StatementsNode (location: (1,16)-(1,19))
        │   │   └── body: (length: 1)
        │   │       └── @ CallNode (location: (1,16)-(1,19))
        │   │           ├── flags: ∅
        │   │           ├── receiver: ∅
        │   │           ├── call_operator_loc: ∅
        │   │           ├── name: :p
        │   │           ├── message_loc: (1,16)-(1,17) = "p"
        │   │           ├── opening_loc: ∅
        │   │           ├── arguments:
        │   │           │   @ ArgumentsNode (location: (1,18)-(1,19))
        │   │           │   ├── flags: ∅
        │   │           │   └── arguments: (length: 1)
        │   │           │       └── @ LocalVariableReadNode (location: (1,18)-(1,19))
        │   │           │           ├── name: :a
        │   │           │           └── depth: 0
        │   │           ├── closing_loc: ∅
        │   │           └── block: ∅
        │   ├── for_keyword_loc: (1,0)-(1,3) = "for"
        │   ├── in_keyword_loc: (1,6)-(1,8) = "in"
        │   ├── do_keyword_loc: (1,13)-(1,15) = "do"
        │   └── end_keyword_loc: (1,21)-(1,24) = "end"
        └── @ ForNode (location: (3,0)-(3,22))
            ├── index:
            │   @ LocalVariableTargetNode (location: (3,4)-(3,5))
            │   ├── name: :a
            │   └── depth: 0
            ├── collection:
            │   @ 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: ∅
            ├── statements:
            │   @ StatementsNode (location: (3,14)-(3,17))
            │   └── body: (length: 1)
            │       └── @ CallNode (location: (3,14)-(3,17))
            │           ├── flags: ∅
            │           ├── receiver: ∅
            │           ├── call_operator_loc: ∅
            │           ├── name: :p
            │           ├── message_loc: (3,14)-(3,15) = "p"
            │           ├── opening_loc: ∅
            │           ├── arguments:
            │           │   @ ArgumentsNode (location: (3,16)-(3,17))
            │           │   ├── flags: ∅
            │           │   └── arguments: (length: 1)
            │           │       └── @ LocalVariableReadNode (location: (3,16)-(3,17))
            │           │           ├── name: :a
            │           │           └── depth: 0
            │           ├── closing_loc: ∅
            │           └── block: ∅
            ├── for_keyword_loc: (3,0)-(3,3) = "for"
            ├── in_keyword_loc: (3,6)-(3,8) = "in"
            ├── do_keyword_loc: ∅
            └── end_keyword_loc: (3,19)-(3,22) = "end"
