> Just a few months ago, I ran into the same problem, although it wasn't caused by `collect()`. It was caused by "normal" `Vec` usage

If it wasn't caused by `collect()`, then I suppose it's a related problem, but not the same problem. Your problem was caused by, as your commit message says, "ignorance [original: ignorant] of the broader effects of this strategy [double-when-full] in aggregate"

The OP's problem, otoh, is more about reusing memory that has been allocated when you "convert" (in Rust term: into_iter()) a Vec to another Vec. What's more, the reuse also happens even when the new Vec has a different type from the original Vec's type. This behavior is more surprising than the double-when-full strategy, which is more widely known by programmers (even if sometimes they "forget" about the implications).