I don't actually use Go, but I have used many other languages where it is like the old behavior. I learned once that I have to build the closure correctly to get the value I want and know now to do it. Don't have any statistics on whether I made that mistake again, but anecdotally I can't remember a case where I have. In their analysis they have found a lot of cases with that mistake, though. So I guess fair enough.

However, I wonder what it will mean if someone who mostly writes Go will now use another language? Will they be more prone to make that mistake?

It's hardly standard behaviour. I mean in Java for example there didn't used to be value types, so everything was a pointer and the effect of this would be the same as the new behaviour in Go.

The only lesson to be learned here is that languages are different. But I think the new Go behaviour is more ergonomic.

In Java you can only close over final variables, so you can't close over the loop variable at all. (Unless that changed since last time I used Java, which - granted - was a long time ago.)

The problem being fixed doesn’t affect only closures, but the body of the for loop itself. So for example taking the address of the loop variable would unexpectedly return the same value for the duration of the loop.