Avoid using RTTI for list tests when possible

With Clang, GCC and MSVC, we can generate the typename using compiler
macros and some string manipulation. Where this is possible, we will use
this instead of RTTI. Where it is not, we will fall back to RTTI and/or
index-based default typename string generation.

Special thanks to Corentin Schreiber ([email protected]) for
the inspiration here.

src/catch2/internal/catch_template_test_registry.hpp

@@ -12,6 +12,7 @@
 #include <catch2/internal/catch_compiler_capabilities.hpp>
 #include <catch2/internal/catch_preprocessor.hpp>
 #include <catch2/internal/catch_meta.hpp>
+#include <catch2/internal/catch_to_string.hpp>
 #include <catch2/internal/catch_unique_name.hpp>
 
 #if defined(CATCH_CONFIG_USE_RTTI) || (defined(CATCH_INTERNAL_RTTI_SUPPORTED) && !defined(CATCH_INTERNAL_USE_NO_RTTI))
@@ -353,6 +354,33 @@ namespace Catch {
     template <typename T>
     struct IndexedTestTypeName {
         std::string operator()(size_t index) const {
+#if defined(CATCH_CONFIG_CPP17_STRING_VIEW) || !defined(CATCH_CONFIG_NO_CPP17_STRING_VIEW)
+    #if defined(__clang__)
+            constexpr auto prefix   = std::string_view{"[T = "};
+            constexpr auto suffix   = "]";
+            constexpr auto function = std::string_view{__PRETTY_FUNCTION__};
+    #elif defined(__GNUC__)
+            constexpr auto prefix   = std::string_view{"with T = "};
+            constexpr auto suffix   = "; ";
+            constexpr auto function = std::string_view{__PRETTY_FUNCTION__};
+    #elif defined(_MSC_VER)
+            constexpr auto prefix   = std::string_view{"get_type_name<"};
+            constexpr auto suffix   = ">(size_t)";
+            constexpr auto function = std::string_view{__FUNCSIG__};
+    #else
+            constexpr std::string_view prefix;
+            constexpr std::string_view suffix;
+            constexpr std::string_view function;
+            if (false) // make sure we don't execute this substr block immediately below
+    #endif
+            {
+                const auto start = function.find(prefix) + prefix.size();
+                const auto end = function.find(suffix, start);
+                const auto size = end - start;
+                return std::string{function.substr(start, size)};
+            }
+#endif
+
 #if defined(CATCH_INTERNAL_USE_RTTI)
             const char* name = typeid(T).name();
             int status = 0;
@@ -361,9 +389,9 @@ namespace Catch {
                 return demangled.get();
             }
 #endif
-            return std::to_string(index);
+            return Catch::to_string<size_t>(index);
         }
     };
-}
+} // namespace Catch
 
 #endif // CATCH_TEMPLATE_TEST_REGISTRY_HPP_INCLUDED