--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/clang/test/Sema/warn-self-assign-field.mm	Thu Feb 13 15:10:13 2020 +0900
@@ -0,0 +1,66 @@
+// RUN: %clang_cc1 -fsyntax-only -Wno-objc-root-class -verify %s
+
+class S {
+ public:
+  int a_;
+  void s(int a) {
+    a_ = a_;  // expected-warning {{assigning field to itself}}
+
+    // Don't really care about this one either way.
+    this->a_ = a_;  // expected-warning {{assigning field to itself}}
+
+    a_ += a_;  // Shouldn't warn.
+  }
+};
+
+void f0(S* s) {
+  // Would be nice to have, but not important.
+  s->a_ = s->a_;
+}
+
+void f1(S* s, S* t) {
+  // Shouldn't warn.
+  t->a_ = s->a_;
+}
+
+struct T {
+  S* s_;
+};
+
+void f2(T* t) {
+  // Would be nice to have, but even less important.
+  t->s_->a_ = t->s_->a_;
+}
+
+void f3(T* t, T* t2) {
+  // Shouldn't warn.
+  t2->s_->a_ = t->s_->a_;
+}
+
+void f4(int i) {
+  // This is a common pattern to silence "parameter unused". Shouldn't warn.
+  i = i;
+
+  int j = 0;
+  j = j;  // Likewise.
+}
+
+@interface I {
+  int a_;
+}
+@end
+
+@implementation I
+- (void)setA:(int)a {
+  a_ = a_;  // expected-warning {{assigning instance variable to itself}}
+}
+
+- (void)foo:(I*)i {
+  // Don't care much about this warning.
+  i->a_ = i->a_;  // expected-warning {{assigning instance variable to itself}}
+
+  // Shouldn't warn.
+  a_ = i->a_;
+  i->a_ = a_;
+}
+@end