I'm not quite caught up on the mailing list - but it looks like the last-minute point about traversing an already-exhausted generator (see [1]) has held.
That's really the most important thing for developers to notice - whether you use the feature often or not, you must be aware that foreach() might throw, not just emit an E_WARNING.
It's a sensible choice and i understand the reason for it being this way. It does seem like it's exposing an implementation detail, though, and out of the rest of the core language syntax, nothing else throws an exception.
I'm happy to see the feature, but this is one of those quirks that, in another five years, will end up in the next "A Fractal Of Bad Design" blog post.
That's really the most important thing for developers to notice - whether you use the feature often or not, you must be aware that foreach() might throw, not just emit an E_WARNING.
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1. https://wiki.php.net/rfc/generators#rewinding_a_generator