[clang] [clang][NFC] Mark CWG2810 as implemented and add a test (PR #194683)

[Victor Chernyakin via cfe-commits]

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@@ -7,6 +7,16 @@
 // RUN: %clang_cc1 -std=c++2c -fexceptions -fcxx-exceptions -pedantic-errors -verify-directives -verify=expected,since-cxx11,since-cxx20,since-cxx23,since-cxx26 %s
 
 
+namespace cwg2810 { // cwg2810: yes
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localspook wrote:

Here's one: https://godbolt.org/z/zsd5PjzYo

https://github.com/llvm/llvm-project/pull/194683