[clang] [clang] Add test for CWG2149 "Brace elision and array length deduction" (PR #90079)

[Vlad Serebrennikov via cfe-commits]

Endilll wrote:

>Can you add examples 14, 16, 17, 18 of the paper?

I'll add them to conformance test suite in a subsequent PR. They don't belong here, as the issue is about deducing array length from brace initializer, but the examples you're listing are focusing on various aspects of how initializer-clauses appertain to aggregate elements.

I can, though, derive more tests from them that check for deduced array length in various appertainment cases, if you feel current coverage of the issue is not sufficient.

https://github.com/llvm/llvm-project/pull/90079