===
Let
===

foo := let (x := a)
           (y := x)
       in
           x
       end;

---

(program
  (definition
    (identifier)
    (expr
      (app_term
        (let
          (binding
            (identifier)
            (expr
              (app_term
                (app
                  (term
                    (identifier))))))
          (binding
            (identifier)
            (expr
              (app_term
                (app
                  (term
                    (identifier))))))
          (expr
            (app_term
              (app
                (term
                  (identifier))))))))))