--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/clang/test/SemaObjCXX/conversion-ranking.mm	Thu Feb 13 15:10:13 2020 +0900
@@ -0,0 +1,90 @@
+// RUN: %clang_cc1 -fsyntax-only -verify %s
+// expected-no-diagnostics
+@protocol P1
+@end
+
+@interface A <P1>
+@end
+
+@interface B : A
+@end
+
+@interface C : B
+@end
+
+template<typename T>
+struct ConvertsTo {
+  operator T() const;
+};
+
+
+// conversion of C* to B* is better than conversion of C* to A*.
+int &f0(A*);
+float &f0(B*);
+
+void test_f0(C *c) {
+  float &fr1 = f0(c);
+}
+
+// conversion of B* to A* is better than conversion of C* to A*
+void f1(A*);
+
+struct ConvertsToBoth {
+private:
+  operator C*() const;
+
+public:
+  operator B*() const;
+};
+
+void test_f1(ConvertsTo<B*> toB, ConvertsTo<C*> toC, ConvertsToBoth toBoth) {
+  f1(toB);
+  f1(toC);
+  f1(toBoth);
+};
+
+// A conversion to an a non-id object pointer type is better than a 
+// conversion to 'id'.
+int &f2(A*);
+float &f2(id);
+
+void test_f2(B *b) {
+  int &ir = f2(b);
+}
+
+// A conversion to an a non-Class object pointer type is better than a 
+// conversion to 'Class'.
+int &f3(A*);
+float &f3(Class);
+
+void test_f3(B *b) {
+  int &ir = f3(b);
+}
+
+// When both conversions convert to 'id' or 'Class', pick the most
+// specific type to convert from.
+void f4(id);
+
+void test_f4(ConvertsTo<B*> toB, ConvertsTo<C*> toC, ConvertsToBoth toBoth) {
+  f4(toB);
+  f4(toC);
+  f4(toBoth);
+}
+
+void f5(id<P1>);
+
+void test_f5(ConvertsTo<B*> toB, ConvertsTo<C*> toC, ConvertsToBoth toBoth) {
+  f5(toB);
+  f5(toC);
+  f5(toBoth);
+}
+
+
+// A conversion to an a non-id object pointer type is better than a 
+// conversion to qualified 'id'.
+int &f6(A*);
+float &f6(id<P1>);
+
+void test_f6(B *b) {
+  int &ir = f6(b);
+}