Sometimes a return statement never returns

[technoblogy]

If the expression in a return statement calls a function that itself uses a return statement, the first return statement never returns. For example:

(defun tst (x)
  (loop
   (return (fun x))))

(defun fun (y)
  (loop
   (return (car y))))

then calling:

(tst '(a b))

should return a, but instead hangs up.

A workaround is to assign the result to a temporary variable, and then return that:

(defun tst (x)
  (loop
   (let ((val (fun x)))
     (return val))))

(defun fun (y)
  (loop
   (return (car y))))

So now, as expected:

> (tst '(a b))
a