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Are there cases where people actually rely on the previous behavior?

I always assumed that it was considered faulty to do so.

There were certainly buggy tests that relied on the old behavior. We didn't find any actual code that relied _correctly_ on the old behavior.

https://go.dev/wiki/LoopvarExperiment

Love it, even though it must have been incredibly confusing when old tests failed at first. The assumption being that the tests were correct. They _passed_ all those months or years!

I'm just also watching your YT video on testing and enjoying it very much!

The tests are in the simplest forms, there are more complex use cases of traditional "for" loops. The complex cases are never explored by the authors of the change.

And there are a large quantity of private Go code in the world.

No convincing evidences to prove there are not such cases. In my honest opinion, if there are such cases in theory, there will be ones in practice. It is a bad expectation to hope such cases never happen in practice.

The authors of the change did try to prove such cases don't happen in practice, but their proving process is totally breaking.

It is my prediction that multiple instances of broken cases will be uncovered in coming years, in addition to the new foot-gun issues created by the altered semantics of transitional 'for' loops.

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