; The following should type-check without errors

(type-check "

let
  lst = list(0,1,true)
in
  unpack a b c = lst
  in
    % Succeeds because c should be bool
    % and both the then and else statements evaluate
    % to the type (listof int int).
    if c
    then cons(a, cons(car(cdr(lst)), emptylist))
    else cons(b, list(a))

")

(type-check "

let
  lst = list(false,10,20)

  % If first element of x is true, return second element, 
  % else return third element.
  p = proc ((listof bool int int) x)
    if car(x) then
      car(cdr(x))
    else
      car(cdr(cdr(x)))
in
  (p lst)

")

(type-check "

let
  lst = emptylist
in
  if null?(lst) then 1 else 2

")