--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/clang/test/SemaTemplate/instantiation-default-1.cpp	Thu Feb 13 15:10:13 2020 +0900
@@ -0,0 +1,102 @@
+// RUN: %clang_cc1 -fsyntax-only -verify %s
+template<typename T, typename U = const T> struct Def1;
+
+template<> struct Def1<int> { 
+  void foo();
+};
+
+template<> struct Def1<const int> { // expected-note{{previous definition is here}}
+  void bar();
+};
+
+template<> struct Def1<int&> {
+  void wibble();
+};
+
+void test_Def1(Def1<int, const int> *d1, Def1<const int, const int> *d2,
+               Def1<int&, int&> *d3) {
+  d1->foo();
+  d2->bar();
+  d3->wibble();
+}
+
+template<typename T,  // FIXME: bad error message below, needs better location info
+         typename T2 = const T*>  // expected-error{{'T2' declared as a pointer to a reference}}
+  struct Def2;
+
+template<> struct Def2<int> { 
+  void foo();
+};
+
+void test_Def2(Def2<int, int const*> *d2) {
+  d2->foo();
+}
+
+typedef int& int_ref_t;
+Def2<int_ref_t> *d2; // expected-note{{in instantiation of default argument for 'Def2<int &>' required here}}
+
+
+template<> struct Def1<const int> { }; // expected-error{{redefinition of 'Def1<const int, const int>'}}
+
+template<typename T, typename T2 = T&> struct Def3;
+
+template<> struct Def3<int> { 
+  void foo();
+};
+
+template<> struct Def3<int&> { 
+  void bar();
+};
+
+void test_Def3(Def3<int, int&> *d3a, Def3<int&, int&> *d3b) {
+  d3a->foo();
+  d3b->bar();
+}
+
+
+template<typename T, typename T2 = T[]> struct Def4;
+
+template<> struct Def4<int> {
+  void foo();
+};
+
+void test_Def4(Def4<int, int[]> *d4a) {
+  d4a->foo();
+}
+
+template<typename T, typename T2 = T const[12]> struct Def5;
+
+template<> struct Def5<int> {
+  void foo();
+};
+
+template<> struct Def5<int, int const[13]> {
+  void bar();
+};
+
+void test_Def5(Def5<int, const int[12]> *d5a, Def5<int, const int[13]> *d5b) {
+  d5a->foo();
+  d5b->bar();
+}
+
+template<typename R, typename Arg1, typename Arg2 = Arg1,
+         typename FuncType = R (*)(Arg1, Arg2)>
+  struct Def6;
+
+template<> struct Def6<int, float> { 
+  void foo();
+};
+
+template<> struct Def6<bool, int[5], float(double, double)> {
+  void bar();
+};
+
+bool test_Def6(Def6<int, float, float> *d6a, 
+               Def6<int, float, float, int (*)(float, float)> *d6b,
+               Def6<bool, int[5], float(double, double),
+                    bool(*)(int*, float(*)(double, double))> *d6c) {
+  d6a->foo();
+  d6b->foo();
+  d6c->bar();
+  return d6a == d6b;
+}