--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/gcc/testsuite/g++.dg/lto/pr83720_0.C	Thu Oct 25 07:37:49 2018 +0900
@@ -0,0 +1,55 @@
+// PR c++/83720
+// { dg-lto-do assemble }
+
+#pragma GCC diagnostic ignored "-Wreturn-type"
+
+namespace b {
+class h {
+public:
+  template <typename ae, typename af> h(ae af::*...) {
+    [] {};
+  }
+};
+class ai {};
+template <typename> class c {
+public:
+  template <typename ag> void aj(const char *, ag f) { h(f, int()); }
+};
+}
+template <typename> class al;
+template <typename e> class i {
+protected:
+  static e g(const int) {  }
+};
+template <typename, typename> class j;
+template <typename an, typename e, typename... ao>
+class j<an(ao...), e> : i<e> {
+  typedef i<e> ap;
+
+public:
+  static an aq(const int &ar, ao... as) { ap::g(ar)(as...); }
+};
+template <typename an, typename... ao> class al<an(ao...)> {
+  template <typename, typename a> using ax = a;
+
+public:
+  template <typename e, typename = ax<int, void>, typename = ax<int, void>>
+  al(e);
+  using ay = an (*)(const int &, ao...);
+  ay az;
+};
+template <typename an, typename... ao>
+template <typename e, typename, typename>
+al<an(ao...)>::al(e) {
+  az = j<an(ao...), e>::aq;
+}
+class k {
+public:
+  k(al<void(b::ai)>);
+} d([](b::ai) {
+  struct be {
+    virtual void f();
+  };
+  struct bf;
+  b::c<bf>().aj("", &be::f);
+});