[clang] [clang] Improve diagnostic on [[nodiscard]] attribute (PR #112521)

[Erich Keane via cfe-commits]

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@@ -17,10 +17,10 @@ E get_e();
 // cxx11-warning at -1 {{use of the 'nodiscard' attribute is a C++17 extension}}
 
 void f() {
-  get_s(); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
+  get_s(); // expected-warning {{ignoring return value of type 'S' declared with 'nodiscard' attribute}}
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erichkeane wrote:

```suggestion
  get_s(); // expected-warning {{ignoring return value type 'S' declared with 'nodiscard' attribute}}
```

https://github.com/llvm/llvm-project/pull/112521