--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/clang/test/SemaTemplate/extern-templates.cpp	Thu Feb 13 15:10:13 2020 +0900
@@ -0,0 +1,80 @@
+// RUN: %clang_cc1 -triple i686-pc-win32 -fsyntax-only -verify %s -DMS
+// RUN: %clang_cc1 -triple x86_64-unknown-linux-gnu-pc-win32 -fsyntax-only -verify %s
+
+template<typename T>
+class X0 {
+public:
+  void f(T t);
+  
+  struct Inner {
+    void g(T t);
+  };
+};
+
+template<typename T>
+void X0<T>::f(T t) {
+  t = 17; // expected-error{{incompatible}}
+}
+
+extern template class X0<int>;
+
+extern template class X0<int*>;
+
+template<typename T>
+void X0<T>::Inner::g(T t) {
+#ifdef MS
+  t = 17; // expected-error{{assigning to 'long *' from incompatible}} expected-error{{assigning to 'int *' from incompatible}}
+#else
+  t = 17; // expected-error{{assigning to 'long *' from incompatible}}
+#endif
+}
+
+void test_intptr(X0<int*> xi, X0<int*>::Inner xii) {
+  xi.f(0);
+#ifdef MS
+  xii.g(0); // expected-note {{instantiation}}
+#else
+  xii.g(0);
+#endif
+}
+
+extern template class X0<long*>; 
+
+void test_longptr(X0<long*> xl, X0<long*>::Inner xli) {
+  xl.f(0);
+  xli.g(0);
+}
+
+template class X0<long*>; // expected-note 2{{instantiation}}
+
+template<typename T>
+class X1 {
+public:
+  void f(T t) { t += 2; }
+  
+  void g(T t);
+};
+
+template<typename T>
+void X1<T>::g(T t) { 
+  t += 2; 
+}
+
+extern template class X1<void*>;
+
+void g_X1(X1<void*> x1, void *ptr) {
+  x1.g(ptr);
+}
+
+extern template void X1<const void*>::g(const void*);
+
+void g_X1_2(X1<const void *> x1, const void *ptr) {
+  x1.g(ptr);
+}
+
+namespace static_const_member {
+  template <typename T> struct A { static const int n; };
+  template <typename T> const int A<T>::n = 3;
+  extern template struct A<int>;
+  int arr[A<int>::n];
+}