[clang] [Clang] Emit a diagnostic note at the class declaration when the method definition does not match any declaration. (PR #110638)

[Vlad Serebrennikov via cfe-commits]

================
@@ -758,16 +759,18 @@ namespace cwg347 { // cwg347: yes
     void g();
   };
 
-  struct derived : base {};
+  struct derived : base {}; // #defined-here-derived
----------------
Endilll wrote:

```suggestion
  struct derived : base {}; // #cwg347-derived
```

https://github.com/llvm/llvm-project/pull/110638