Exercise 3: A Program With No Garbage — Possible Solution
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THE PROGRAM
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    fun makeAdder(x) {
        fun adder(y) { return x + y; }
        return adder;
    }
    var a = makeAdder(10);
    var b = makeAdder(20);
    var c = makeAdder(30);
    print a(1);
    print b(1);
    print c(1);

RESULT
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    output: ['11', '21', '31']
    heap before collect_garbage(): 8
    collect_garbage() collects: 1
    heap after: 7

WHY IT ISN'T ZERO
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Every object the WISP PROGRAM itself created is genuinely reachable:
makeAdder's own closure via the global 'makeAdder', and each of the
three (Upvalue, Closure) pairs via globals 'a', 'b', and 'c'. None of
that -- 7 objects total -- gets touched.

The one object collected is, once again, the top-level script's own
Closure (object #1, in this exercise's own numbering, matching
Exercise 1's own finding). It was only ever reachable through
self.frames while the script itself was actively running; once
run() returns, self.frames is empty, and nothing else in the whole
program -- not globals, not any surviving closure's own upvalues --
ever pointed at the script's own closure to begin with. It was never
part of the "real" Wisp program's own data; it was scaffolding this
course's own compile_and_run() helper needed to get the program
started at all.

WHY THIS WORKS AS AN ANSWER
------------------------------
This confirms the collector behaves correctly at the boundary case
that matters most for trust: when nothing is actually garbage, it
doesn't invent any. The single object it does collect isn't a false
positive -- it's a real, honestly unreachable object, just one this
exercise's own framing ("no garbage from the WISP program") didn't
originally count, the same oversight Exercise 1 already flagged. A
collector that swept zero objects here would be just as correct in
spirit; the fact that it correctly finds exactly the one genuinely
dead object, and nothing else, is the actual demonstration of
correctness -- not the raw number itself.