[clang] [clang] Validate return type when instantiating `returns_nonnull` atttribute (PR #200117)

[Corentin Jabot via cfe-commits]

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@@ -1013,6 +1013,17 @@ void Sema::InstantiateAttrs(const MultiLevelTemplateArgumentList &TemplateArgs,
       continue;
     }
 
+    if (auto *A = dyn_cast<ReturnsNonNullAttr>(TmplAttr)) {
+      auto *FD = cast<FunctionDecl>(New);
+      QualType ResultType = getFunctionOrMethodResultType(FD);
+      if (!isValidPointerAttrType(ResultType))
+        Diag(A->getLocation(), diag::warn_attribute_return_pointers_only)
+            << A << SourceRange() << getFunctionOrMethodResultSourceRange(FD);
+      else if (!New->hasAttr<ReturnsNonNullAttr>())
+        New->addAttr(A->clone(Context));
+      continue;
+    }
+
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cor3ntin wrote:

we have a `attrNonNullArgCheck` function - could we reuse  that?

https://github.com/llvm/llvm-project/pull/200117