Wibble...

The corrected example is as follows:

myS :: (forall t t1 t2. (t -> t2 -> t1) -> (t -> t2) -> t -> t1)
[NoDiscard] __AL 3
myS
  = \ @ t @ t1 @ t2 f :: (t -> t2 -> t1) g :: (t -> t2) x :: t -> f x (g x)

public class myS implements Code {
  public Object ENTER () {
    VM.COLLECT(3, this);
    final Object f = VM.POP();
    final Object g = VM.POP();
    final Object x = VM.POP();
    VM.PUSH(x);
    VM.PUSH(new Thunk(new myS$1(g, x)));
    return f;
  }
}
class myS$1 extends Code {
  final Object g;
  final Object x;
  public myS$1 (Object _g_, Object _x_) {
    g = _g_;
    x = _x_;
  }
  public Object ENTER () {
    VM.PUSH(x);
    return g;
  }
}