Fix issue 4957 - std.concurrency rejects structs with Tid

[Geod24]

In addition to the fix which makes it recurse in struct,
the instantiation was changed to not use recursive template instantiation,
exception for struct's tupleof.

[bithavoc]

I hope this gets merged, this and https://issues.dlang.org/show_bug.cgi?id=5570 made me feel that Dlang was not stable enough a few years back. I've seen more activity in these bug reports these days, I'm feeling tempted to try Dlang again ☕️ .

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Bugzilla references

Auto-close	Bugzilla	Severity	Description
✓	4957	normal	std.concurrency does not allow to pass Tid in struct fields

Testing this PR locally

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

dub fetch digger
dub run digger -- build "master + phobos#6738"

[AndrejMitrovic]

the instantiation was changed to not use recursive template instantiation

But doesn't the old code short-circuit, and yours does not? Then again maybe the performance is ultimately better because of a lack of recursive template instantiations.. ¯\_(ツ)_/¯

[n8sh]

Including short-circuiting would be nice, but I'll approve this even without.

[Geod24]

Is there a way to short-circuit without recursive instantiation ?

[n8sh]

Is there a way to short-circuit without recursive instantiation ?

In my experience you can write doesIt |= ...; if (doesIt) return true; without triggering an unreachable code check.

[Geod24]

Don't think this has much influence, because by the time the code is run at CTFE all we have is doesIt |= [true|false] so we're just assigning from a constant. Evaluating the template is what we should really short-circuit, but we can't do that with CTFE.

[n8sh]

For the benefit of dlang-bot I edited the commit message to start "Fix Issue 4957" instead of "Fix 4957", but that's been clobbered. Please make that change.

[Geod24]

I did already, but dlang-bot doesn't seem to realize this.

[Geod24]

@n8sh : Ah, commit message, not PR title. Sorry. Thanks for the fix!

[wilzbach]

Yep that's needed to aggregate the changelog entries over commit messages