moveEmplace: optimise and make it betterC friendly

[9il]

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[dlang-bot]

Thanks for your pull request, @9il!

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[thewilsonator]

Please also update the Phobos copy as wells they don't get out of sync.

[9il]

btw, why Phobos just does not import core.lifetime?

[9il]

dlang/phobos#6964

[thewilsonator]

Phobos has a check for no internal pointers or something that can't be in druntime because it depends on too much of phobos.

[9il]

Is it because of optimization reasons?

[thewilsonator]

No, its because druntime cannot depend on phobos.

[9il]

Yes, but phobos can depend on druntime. Why not to use public imports?

[jacob-carlborg]

Yes, but phobos can depend on druntime. Why not to use public imports?

Because the implementation is not the same.

[wilzbach]

Druntime would need this to match the Phobos implementation: #2447

[9il]

I closed it because of the same change in Phobos fails.