memo:
```bash
> ruby -e 'v&.to_i' --parser=prism --dump=parsetree
@ ProgramNode (location: (1,0)-(1,7))
+-- locals: []
+-- statements:
    @ StatementsNode (location: (1,0)-(1,7))
    +-- body: (length: 1)
        +-- @ CallNode (location: (1,0)-(1,7))
            +-- CallNodeFlags: safe_navigation
            +-- receiver:
            |   @ CallNode (location: (1,0)-(1,1))
            |   +-- CallNodeFlags: variable_call, ignore_visibility
            |   +-- receiver: nil
            |   +-- call_operator_loc: nil
            |   +-- name: :v
            |   +-- message_loc: (1,0)-(1,1) = "v"
            |   +-- opening_loc: nil
            |   +-- arguments: nil
            |   +-- closing_loc: nil
            |   +-- block: nil
            +-- call_operator_loc: (1,1)-(1,3) = "&."
            +-- name: :to_i
            +-- message_loc: (1,3)-(1,7) = "to_i"
            +-- opening_loc: nil
            +-- arguments: nil
            +-- closing_loc: nil
            +-- block: nil
```