[PATCH] D139095: [clang] Mark CWG405 as a duplicate of CWG218

[Vlad Serebrennikov via Phabricator via cfe-commits]

Endill added a comment.

>> We can do it the following way then: // dr405: yes \n // NB: also dup 218.
>
> That would be fine by me!

Which way should we handle this? I'd prefer to do it without test duplication, but making it clear for readers is a serious concern indeed. (Read on, I elaborate on this below.)

>> What test for 405 is going to be if not a copy-and-paste of a part of 218 test?
>
> In terms of test *coverage*, no benefit. In terms of *implementation status*, it makes it clear we considered the DR explicitly instead of leaving future folks to wonder.

Should we really try to meet an expectation that Clang developers haven't considered something as obvious as explicitly handling a DR not marked as duplicated or superseded officially? It doesn't seem a reasonable expectation to me, and at least my personal attitude have always been the opposite.
To be fully honest here, I don't even remember myself how I came across CWG218, because I did this test back in spring. So marking it as a duplicate (one way or another) on the contrary seems very considerate handling.

> CodeGen tests would be the approach I'd take; that's not actually testing the backend behavior, that's still testing the frontend IR generation (which is before the backend gets to start mutating/optimizing it).

You're very much right. Thank you for reminding me of that!


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