Hot take: Rust doesn't go far enough with explicit clone; dropping any type that isn't trivially copiable should also be explicit. I don't mean that it should be leaked if you don't delete it, I mean that the compiler should force you to explicitly say

"I am done with this object, anything that had to know about it has already been notified and either there isn't a single last point of use or it isn't a clone, therefore dropping is justified."

This is the whole meaning of dropping a complex object. I think that this is far too strong a statement to imply in bulk for every value in scope at the end of the function.