[clang] [libcxx] [Clang] Implement CWG2137 (list-initialization from objects of the same type) (PR #94355)

[Mital Ashok via cfe-commits]

MitalAshok wrote:

Note that only a single line has changed from the previous PR: https://github.com/llvm/llvm-project/commit/d90534729d34da86bb01c4ddc272310f0f0b4ce4#diff-19c518dbc68b30c66e1a2b6bd523c005fb2050dcf1a0e92305df7ab3e1b9e9f3L1653

I was waiting on a proper resolution for CWG2311, but the (identical/duplicate?) CWG2742 claims that "The consensus is to try an initializer-list constructor first and then fall back to copy-initialization", which is what this does. This is still slightly different from what GCC does.


https://github.com/llvm/llvm-project/pull/94355