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

[Yihe Li via cfe-commits]

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@@ -9300,6 +9300,12 @@ def warn_unused_container_subscript_expr : Warning<
 def warn_unused_call : Warning<
   "ignoring return value of function declared with %0 attribute">,
   InGroup<UnusedValue>;
+def warn_unused_return_type : Warning<
+  "ignoring %select{return value|temporary}0 of type %2 declared with %1 attribute">,
+  InGroup<UnusedValue>;
+def warn_unused_return_type_msg : Warning<
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Mick235711 wrote:

I originally wanted to do this, but existing `warn_unused_constructor` and `warn_unused_result` all have a separate `_msg` version... If we fold together the two `unused_return_type`s, should these two be folded together too?

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