Make QueryParIter::for_each_unchecked private

[JoJoJet]

Objective

• The function QueryParIter::for_each_unchecked is a footgun: the only ways to use it soundly can be done in safe code using for_each or for_each_mut. See this discussion on discord.

Solution

• Make for_each_unchecked private.

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Changelog

• Removed QueryParIter::for_each_unchecked. All use-cases of this method were either unsound or doable in safe code using for_each or for_each_mut.

Migration Guide

The method QueryParIter::for_each_unchecked has been removed -- use for_each or for_each_mut instead. If your use case can not be achieved using either of these, then your code was likely unsound.

If you have a use-case for for_each_unchecked that you believe is sound, please open an issue.

[alice-i-cecile]

I agree with this analysis. Changelog would be clearer if it talked about how this is no longer public, rather than that it was removed IMO. Took me a bit to figure out exactly what happened looking at the diff!

[JoJoJet]

My reasoning is that from the perspective of someone using bevy_ecs, this method has effectively been removed. I agree it's probably good to change the title though.