[clang] [Clang] Check explicit object parameter for defaulted operators properly (PR #100419)

[Vlad Serebrennikov via cfe-commits]

================
@@ -92,6 +92,26 @@ using ::cwg2521::operator""_div;
 #endif
 } // namespace cwg2521
 
+namespace cwg2547 { // cwg2547: 20
+#if __cplusplus >= 202302L
+struct S; // since-cxx23-note 3 {{forward declaration of 'cwg2547::S'}}
+bool operator==(S, S) = default;  // error: S is not complete
+// since-cxx23-error at -1 2 {{variable has incomplete type 'S'}}
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Endilll wrote:

```suggestion
// since-cxx23-error at -1 {{variable has incomplete type 'S'}}
// since-cxx23-error at -2 {{variable has incomplete type 'S'}}
```
We don't use diagnostic quantifiers in DR test suite

https://github.com/llvm/llvm-project/pull/100419