fix abi (again)

Author: cor3ntin

clang/include/clang/Sema/Sema.h

@@ -10673,7 +10673,7 @@ class Sema final : public SemaBase {
 
 
   // Unused, kept in Clang 20 for ABI stability.
-  void DiagnoseDiscardedExprMarkedNodiscard(const Expr *E) {};
+  void DiagnoseDiscardedExprMarkedNodiscard(const Expr *E);
 
   /// DiagnoseUnusedExprResult - If the statement passed in is an expression
   /// whose result is unused, warn.

clang/lib/Sema/SemaStmt.cpp

@@ -413,6 +413,10 @@ void DiagnoseUnused(Sema &S, const Expr *E, std::optional<unsigned> DiagID) {
 }
 } // namespace
 
+void Sema::DiagnoseDiscardedExprMarkedNodiscard(const Expr *E) {
+  DiagnoseUnused(*this, E, std::nullopt);
+}
+
 void Sema::DiagnoseUnusedExprResult(const Stmt *S, unsigned DiagID) {
   if (const LabelStmt *Label = dyn_cast_if_present<LabelStmt>(S))
     S = Label->getSubStmt();