How is defer timed with recursive calls?

Using Swift
1

My code for a loop-less sequence-on-filter-sequence method required me to add a do-block to prevent infinite recursion. It seems that if a return path involves a (tail?) recursive call, then outstanding defer blocks don't trigger until the recursive call finishes. Since my code needed the increment(s) to happen before the recursion, I added the do structuring.

Am I understanding it correctly?

2

That sounds correct. defer happens "at the return (or break or continue)" or "at the close brace", and that means after any recursive calls to compute the value to return.