Yield without value in reference generator should create notice

[Bellangelo]

Fixes #16761

[dstogov]

I'm not sure if this is necessary.
@cmb69 @nielsdos please make a decision

[cmb69]

php-src/Zend/zend_vm_def.h

Lines 8138 to 8139 in 173175b

	/* Constants and temporary variables aren't yieldable by reference,
	* but we still allow them with a notice. */

I think the question is whether this behavior is supposed to be deprecated/removed at some point in the future. If so, having the notice in the else branch appears to be prudent. If not, we may drop the other notices instead; that would make the behavior consistent.

[Bellangelo]

If not, we may drop the other notices instead; that would make the behavior consistent.

@cmb69 If we agree on this, it might be a good idea to do this in a new version. I don't think that we should change the behavior of the pre-existing versions.

[nielsdos]

I think the question is whether this behavior is supposed to be deprecated/removed at some point in the future. If so, having the notice in the else branch appears to be prudent. If not, we may drop the other notices instead; that would make the behavior consistent.

I would agree. I also agree with @Bellangelo but would make it stronger in the sense that perhaps, since this is a behaviour change, whatever we choose has to go in master anyway. Perhaps we should consult the mailing list to ask for opinion on whether the notice should be added or not.

[cmb69]

Perhaps we should consult the mailing list to ask for opinion on whether the notice should be added or not.

@Bellangelo, would you want to start this discussion?

[Bellangelo]

@Bellangelo, would you want to start this discussion?

Sure.