Even so, you need to be able to make a very specific formal declaration of exactly what constructs result in the optimization being non-leaky. It needs to be c

Even so, you need to be able to make a very specific formal declaration of exactly what constructs result in the optimization being non-leaky. It needs to be completely straightfoward and easy enough to understand that no programmer gets into the situation where they think a leaky optimization is non-leaky. And once you make an optimization non-leaky, it cannot ever become leaky again in any particular situation whatsoever, or it could break existing programs.