[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]

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@@ -600,6 +600,7 @@ namespace cwg336 { // cwg336: yes
     template<> template<class X> class A<int>::B {};
     template<> template<> template<class T> void A<int>::B<double>::mf1(T t) {}
     // expected-error at -1 {{out-of-line definition of 'mf1' does not match any declaration in 'cwg336::Pre::A<int>::B<double>'}}
+    // expected-note at -3 {{defined here}}
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Endilll wrote:

```suggestion
    //   expected-note@#cwg366-blah {{defined here}}
```

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