[clang] [Clang][Sema] Reject array prvalue operands (PR #140702)

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languagelawyer wrote:

> This is related to CWG2548

Kinda, but not really. It has never been necessary to create the (non-)issue. Or does someone really believe that it is a C++ defect that `IA{ 1, 2, 3 } - IA{ 1, 2, 3 }` is not allowed?

https://github.com/llvm/llvm-project/pull/140702