--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/gcc/testsuite/g++.dg/cpp0x/overload-conv-3.C	Thu Feb 13 11:34:05 2020 +0900
@@ -0,0 +1,21 @@
+// PR c++/86521
+// { dg-do compile { target c++11 } }
+
+template <class T> T&& move (T&);
+
+struct Dest {
+  Dest() = default;
+  Dest( Dest && ) = default;
+  Dest( Dest const & ) = delete;
+};
+
+struct Source {
+  Dest val;
+  operator Dest () && { return move( val ); }
+  operator Dest const & () const & { return val; }
+};
+
+int main() {
+  Source x;
+  Dest d(move(x));	   // { dg-error "ambiguous" "" { target c++14_down } }
+}