Sema: Simplify the check if a method returns an instance of the class.

Just checking if the parent of the method is the same as the return type
should be sufficient. Also fixes PR17587.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@192802 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Sema/SemaDecl.cpp b/lib/Sema/SemaDecl.cpp
index daf135a..c653763 100644
--- a/lib/Sema/SemaDecl.cpp
+++ b/lib/Sema/SemaDecl.cpp
@@ -6911,7 +6911,9 @@
   if (!NewFD->isInvalidDecl() && !NewFD->hasAttr<WarnUnusedResultAttr>() &&
       Ret && Ret->hasAttr<WarnUnusedResultAttr>()) {
     const CXXMethodDecl *MD = dyn_cast<CXXMethodDecl>(NewFD);
-    if (!(MD && MD->getCorrespondingMethodInClass(Ret, true))) {
+    // Attach the attribute to the new decl. Don't apply the attribute if it
+    // returns an instance of the class (e.g. assignment operators).
+    if (!MD || MD->getParent() != Ret) {
       NewFD->addAttr(new (Context) WarnUnusedResultAttr(SourceRange(),
                                                         Context));
     }