Add missing testcase cpp11_template_parameters_decltype

Examples/test-suite/cpp11_template_parameters_decltype.i

@@ -0,0 +1,51 @@
+%module cpp11_template_parameters_decltype
+
+%include <std_string.i>
+%include <std_vector.i>
+%include <std_pair.i>
+
+#pragma SWIG nowarn=SWIGWARN_CPP11_DECLTYPE
+
+#if 0
+// to fix (non-template expression equivalent to template expression further down):
+%inline %{
+#include <utility>
+#include <vector>
+  void f(bool c = std::is_constructible<std::string, decltype(std::declval<std::vector<std::pair<int, int>>>().begin()->first)>::value) {}
+%}
+#endif
+
+%inline %{
+// Github issue #1590
+struct Converter {
+  std::string to_json() const {}
+};
+struct Json {
+  Json(std::string s) {}
+  template < class T, class = decltype(&T::to_json) >
+    Json(const T & t) : Json(t.to_json()) {}
+
+// Github issue #1589
+// To fix
+#if !defined(SWIG)
+  // Implicit constructor: map-like objects (std::map, std::unordered_map, etc)
+  template <class M, typename std::enable_if<
+      std::is_constructible<std::string, decltype(std::declval<M>().begin()->first)>::value,
+      int>::type = 0>
+          Json(const M & m) : Json(object(m.begin(), m.end())) {}
+#endif
+};
+%}
+
+// %template(Json) Json::Json<Converter>; // not working
+%template(Json) Json::Json<Converter, std::string>; // workaround
+
+
+%inline %{
+// Github issue #1589
+template <decltype(true) X = true>
+void A() { }
+%}
+
+// %template(A) A<>; // not working
+%template(A) A<true>; // workaround