[clang] [Clang] Implement diagnostics for why is_empty is false (PR #145044)

[Corentin Jabot via cfe-commits]

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@@ -644,6 +644,10 @@ Improvements to Clang's diagnostics
   #GH69470, #GH59391, #GH58172, #GH46215, #GH45915, #GH45891, #GH44490,
   #GH36703, #GH32903, #GH23312, #GH69874.
 
+- Clang now gives pinpointed diagnostics for std::is_empty<T> failures—emitting a “not empty” error 
+  plus “because…” notes for non-static members, virtual functions/bases, non-empty bases, and non-zero bit-fields 
+  (including dependent widths) while correctly ignoring zero-width bit-fields. 
+
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cor3ntin wrote:

Same comment as on the other PR, we should just add an entry for the general feature

https://github.com/llvm/llvm-project/pull/145044