[PATCH] D98477: [ADT] Add IntrusiveVariant, VariantTraits, and new STLForwardCompat

[Scott Linder via Phabricator via llvm-commits]

scott.linder added a comment.

In D98477#2780702 <https://reviews.llvm.org/D98477#2780702>, @dblaikie wrote:

> Side thought: If this is going to use a prefix for the discriminator - could that be a base class that all types being used as union members have to derive from? No need for a macro, etc. Could use an offsetof comparison to make sure that not only is it a base class, but the first non-empty base class.
>
> (still haven't been able to easily apply this locally - looks like it hit a conflict with c6f20d70a8c93ab3d50c9777c477fe040460a664 <https://reviews.llvm.org/rGc6f20d70a8c93ab3d50c9777c477fe040460a664> - though I thought arc would sync to the right version to apply the patch... not sure what's going on - might just wait to try that until the other patches have been committed)

Unfortunately having any non-static data members as part of a base class will make the alternative types non-standard-layout, which means we can't use the "common initial sequence" rule to pack them.


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https://reviews.llvm.org/D98477