Expect transformation lost a binder

[ccshan]

$ cat try.hk
expect
  _ <~
    x <~ y <~ lebesgue(-inf,inf)
         if 0<y: dirac(y) else: reject.measure(real)
    dirac(x)
  : 1
$ pretty try.hk 
x3 = -prob2real(∞)
x4 = prob2real(∞)
if nat2real(0) < x5: nat2prob(1) else: 0/1

The variable x5 produced above is unbound.

[zaxtax]

The correct output should be the following right?

x3 = -prob2real(∞)
x4 = prob2real(∞)
integrate x5 from x3 to x4:
    if nat2real(0) < x5: nat2prob(1) else: 0/1

[ccshan]

That output is correct!

[zaxtax]

Ok I think my recent change fixed the problem, but I'm not entirely confident if my change is the correct thing to do. I'm looking over Preserving Sharing in the Partial Evaluation of Lazy Functional Programs to see if I should have residualized the heap somewhere else instead.