Proving that is impossible. As said before, rsc has analyzed publicly available source and found the change fixed bugs in the ones where it made any difference.
If you want to argue, you really need to show an example of where the change causes a bug in any scenario that matters. With a real, preexisting, program.
If it is impossible, why do you ask me that question?
I totally disagree with your logic. I think you don't have the right logic here.
At least, the proposal should be accepted when the experiment period has lasted for a year. But now, the proposal has been accepted before the experiment period started. Is it weird?
Proving the non-existence of a proprietary source file somewhere that contains code which will become buggy with this experiment is impossible; we don't know all the source code in the world.
Proving the existence of a program that contains code which will become buggy is easy: share the code. Show actual program code, not a hypothetical; nobody is saying the experiment doesn't change behavior, people are saying it only changes behavior that doesn't matter to real world code.
On real world code discovered so far, the experiment would fix bugs.
Your logic is too illogical. It is the proposal's supporters' responsibility to prove the proposal doesn't do harm. If they are unable to do this, please don't pretend that this has been proven, and please just stop making any arguments.
It is not my (and all other Go programmers') responsibility to do this. Here, I just shows the possibility that the proposal will do harm, and help others to find the broken cases easily. However, surely, Go programmers, in their spare time, can help the proposal's supporters to do this. But, again, it is strange that the proposal has been accepted before such attempts are made. :D, so weird.
And, please read my tweets, there are several factors which are unrelated to finding broken code. In fact, the change will lead to more error-prone, instead of less error-prone.
If you want to argue, you really need to show an example of where the change causes a bug in any scenario that matters. With a real, preexisting, program.