Follow-up to #49 to move catchall overload up

And add regression tests for the compositions enabled by #49

Author: hsutter

include/cpp2util.h

@@ -751,6 +751,10 @@ template <class F>
 //
 //-----------------------------------------------------------------------
 //
+inline auto to_string(...) -> std::string {
+    return "(customize me - no cpp2::to_string overload exists for this type)";
+}
+
 template<typename T>
 inline auto to_string(T const& t) -> std::string
     requires requires { std::to_string(t); }
@@ -824,10 +828,6 @@ inline auto to_string(std::tuple<Ts...> const& t) -> std::string
     }
 }
 
-inline auto to_string(...) -> std::string {
-    return "(customize me - no cpp2::to_string overload exists for this type)";
-}
-
 
 //-----------------------------------------------------------------------
 //

regression-tests/mixed-string-interpolation.cpp2

@@ -3,6 +3,8 @@
 #include <utility>
 #include <tuple>
 
+struct custom_struct_with_no_stringize_customization { } custom;
+
 main: () -> int = {
     a := 2;
     b: std::optional<int> = ();
@@ -35,4 +37,15 @@ main: () -> int = {
     std::cout << "tup1 = (tup1)$\n";
     std::cout << "tup2 = (tup2)$\n";
     std::cout << "tup3 = (tup3)$\n";
+
+    p: std::pair<std::string_view, std::optional<std::string>> = ("first", std::nullopt);
+    std::cout << "p = (p)$\n";
+
+    t: std::tuple<double, std::optional<std::pair<std::string_view, int>>, std::optional<std::tuple<int, int, int>>> = (3.14, std::nullopt, std::nullopt);
+    std::cout << "t = (t)$\n";
+
+    vv: std::variant<int, std::string, std::pair<int, double> > = ();
+    std::cout << "vv = (vv)$\n";
+
+    std::cout << "custom = (custom)$\n";
 }

regression-tests/test-results/mixed-string-interpolation.cpp

@@ -7,11 +7,13 @@
 #include <utility>
 #include <tuple>
 
+struct custom_struct_with_no_stringize_customization { } custom;
+
 [[nodiscard]] auto main() -> int;
 
 //=== Cpp2 definitions ==========================================================
 
-#line 5 "mixed-string-interpolation.cpp2"
+#line 7 "mixed-string-interpolation.cpp2"
 
 [[nodiscard]] auto main() -> int{
     auto a { 2 }; 
@@ -45,4 +47,15 @@
     std::cout << "tup1 = " + cpp2::to_string(tup1) + "\n";
     std::cout << "tup2 = " + cpp2::to_string(tup2) + "\n";
     std::cout << "tup3 = " + cpp2::to_string(tup3) + "\n";
+
+    std::pair<std::string_view,std::optional<std::string>> p { "first", std::nullopt }; 
+    std::cout << "p = " + cpp2::to_string(p) + "\n";
+
+    std::tuple<double,std::optional<std::pair<std::string_view,int>>,std::optional<std::tuple<int,int,int>>> t { 3.14, std::nullopt, std::nullopt }; 
+    std::cout << "t = " + cpp2::to_string(t) + "\n";
+
+    std::variant<int,std::string,std::pair<int,double>> vv {  }; 
+    std::cout << "vv = " + cpp2::to_string(vv) + "\n";
+
+    std::cout << "custom = " + cpp2::to_string(custom) + "\n";
 }