Fix Issue 23561 - std.typecons.Unique!struct does not destroy struct …

[ntrel]

…instance

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Bugzilla references

Auto-close	Bugzilla	Severity	Description
✓	23561	normal	std.typecons.Unique!struct does not destroy struct instance

Testing this PR locally

If you don't have a local development environment setup, you can use Digger to test this PR:

dub run digger -- build "master + phobos#8651"

[ntrel]

Is there a better way of checking for this?

[RazvanN7]

why is this needed?

[ntrel]

destroy calls the destructor first, before nullifying the context pointer (I think). Then when the GC calls the destructor it segfaults when accessing i to increment it, because the context pointer is null.

[pbackus]

This works for me:

Suggested change

	if (&i > cast(void*) 1024)
	if (this !is typeof(this).init)

[ntrel]

OK. I asked on the learn forum for a way that works well in general and @aG0aep6G suggested using tupleof[$-1], so I've used tupleof[0] as tupleof.length here is 1.

[ljmf00]

Squash the commits before merge.

[ntrel]

@ljmf00 Razvan has used auto-merge-squash.

[ntrel]

Added a separate changelog with a note about the GC calling the destructor too: #8654.

[ibuclaw]

This PR caused a regression https://issues.dlang.org/show_bug.cgi?id=23723