[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]

================
@@ -1009,18 +1012,20 @@ namespace cwg355 { struct ::cwg355_S s; }
 // cwg356: na
 
 namespace cwg357 { // cwg357: yes
-  template<typename T> struct A {
+  template<typename T> struct A { // #defined-here-cwg357-A
----------------
Endilll wrote:

```suggestion
  template<typename T> struct A { // #cwg357-A
```

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