And a whole lot of "wait, what tree does this code map to again?"

With lisp, there's no difficulty mapping:

   int main(int x) {foo()}

to

  Method m = new Method(return:=new Type(int),
                        args  := new ArgList(
                                  new Arg(new Type(int),
                                          new Name("x"))),
                        body  := new Block(

.... I'm sure you get the point....

The syntax tree is apparent from the syntax.

  (+ 1 2 (* 3 4))

Maps to:

  '(+ 1 2 (* 3 4))