1 files changed, 15 insertions, 2 deletions
diff --git a/clang/lib/Sema/SemaDeclAttr.cpp b/clang/lib/Sema/SemaDeclAttr.cpp
index b7ca9924ef1..ff4192e91d3 100644
--- a/clang/lib/Sema/SemaDeclAttr.cpp
+++ b/clang/lib/Sema/SemaDeclAttr.cpp
@@ -1292,13 +1292,26 @@ static void handleOwnershipAttr(Sema &S, Decl *D, const AttributeList &AL) {
 
     // Check we don't have a conflict with another ownership attribute.
     for (const auto *I : D->specific_attrs<OwnershipAttr>()) {
-      // FIXME: A returns attribute should conflict with any returns attribute
-      // with a different index too.
+      // Cannot have two ownership attributes of different kinds for the same
+      // index.
       if (I->getOwnKind() != K && I->args_end() !=
           std::find(I->args_begin(), I->args_end(), Idx)) {
         S.Diag(AL.getLoc(), diag::err_attributes_are_not_compatible)
           << AL.getName() << I;
         return;
+      } else if (K == OwnershipAttr::Returns &&
+                 I->getOwnKind() == OwnershipAttr::Returns) {
+        // A returns attribute conflicts with any other returns attribute using
+        // a different index. Note, diagnostic reporting is 1-based, but stored
+        // argument indexes are 0-based.
+        if (std::find(I->args_begin(), I->args_end(), Idx) == I->args_end()) {
+          S.Diag(I->getLocation(), diag::err_ownership_returns_index_mismatch)
+              << *(I->args_begin()) + 1;
+          if (I->args_size())
+            S.Diag(AL.getLoc(), diag::note_ownership_returns_index_mismatch)
+                << (unsigned)Idx + 1 << Ex->getSourceRange();
+          return;
+        }
       }
     }
     OwnershipArgs.push_back(Idx);