From fc320f6b8f55b8781a5e039ff0cad23c578568c2 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Martin=20Ho=C5=99e=C5=88ovsk=C3=BD?=
 <martin.horenovsky@gmail.com>
Date: Mon, 28 Oct 2019 15:06:54 +0100
Subject: [PATCH] Extract FunctionReturnType to catch_meta.hpp

---
 include/internal/catch_generators_generic.hpp | 14 ++------
 include/internal/catch_meta.hpp               | 36 ++++++++++++-------
 2 files changed, 26 insertions(+), 24 deletions(-)

diff --git a/include/internal/catch_generators_generic.hpp b/include/internal/catch_generators_generic.hpp
index 81fd3857..c3410147 100644
--- a/include/internal/catch_generators_generic.hpp
+++ b/include/internal/catch_generators_generic.hpp
@@ -8,6 +8,7 @@
 #define TWOBLUECUBES_CATCH_GENERATORS_GENERIC_HPP_INCLUDED
 
 #include "catch_generators.hpp"
+#include "catch_meta.hpp"
 
 namespace Catch {
 namespace Generators {
@@ -172,18 +173,7 @@ namespace Generators {
         }
     };
 
-#if defined(__cpp_lib_is_invocable) && __cpp_lib_is_invocable >= 201703
-    // std::result_of is deprecated in C++17 and removed in C++20. Hence, it is
-    // replaced with std::invoke_result here. Also *_t format is preferred over
-    // typename *::type format.
-    template <typename Func, typename U>
-    using MapFunctionReturnType = std::remove_reference_t<std::remove_cv_t<std::invoke_result_t<Func, U>>>;
-#else
-    template <typename Func, typename U>
-    using MapFunctionReturnType = typename std::remove_reference<typename std::remove_cv<typename std::result_of<Func(U)>::type>::type>::type;
-#endif
-
-    template <typename Func, typename U, typename T = MapFunctionReturnType<Func, U>>
+    template <typename Func, typename U, typename T = FunctionReturnType<Func, U>>
     GeneratorWrapper<T> map(Func&& function, GeneratorWrapper<U>&& generator) {
         return GeneratorWrapper<T>(
             pf::make_unique<MapGenerator<T, U, Func>>(std::forward<Func>(function), std::move(generator))
diff --git a/include/internal/catch_meta.hpp b/include/internal/catch_meta.hpp
index 8529766d..4eca7efc 100644
--- a/include/internal/catch_meta.hpp
+++ b/include/internal/catch_meta.hpp
@@ -12,22 +12,34 @@
 #include <type_traits>
 
 namespace Catch {
-template<typename T>
-struct always_false : std::false_type {};
+    template<typename T>
+    struct always_false : std::false_type {};
+
+    template <typename> struct true_given : std::true_type {};
+    struct is_callable_tester {
+        template <typename Fun, typename... Args>
+        true_given<decltype(std::declval<Fun>()(std::declval<Args>()...))> static test(int);
+        template <typename...>
+        std::false_type static test(...);
+    };
+
+    template <typename T>
+    struct is_callable;
 
-template <typename> struct true_given : std::true_type {};
-struct is_callable_tester {
     template <typename Fun, typename... Args>
-    true_given<decltype(std::declval<Fun>()(std::declval<Args>()...))> static test(int);
-    template <typename...>
-    std::false_type static test(...);
-};
+    struct is_callable<Fun(Args...)> : decltype(is_callable_tester::test<Fun, Args...>(0)) {};
 
-template <typename T>
-struct is_callable;
 
-template <typename Fun, typename... Args>
-struct is_callable<Fun(Args...)> : decltype(is_callable_tester::test<Fun, Args...>(0)) {};
+#if defined(__cpp_lib_is_invocable) && __cpp_lib_is_invocable >= 201703
+    // std::result_of is deprecated in C++17 and removed in C++20. Hence, it is
+    // replaced with std::invoke_result here. Also *_t format is preferred over
+    // typename *::type format.
+    template <typename Func, typename U>
+    using FunctionReturnType = std::remove_reference_t<std::remove_cv_t<std::invoke_result_t<Func, U>>>;
+#else
+    template <typename Func, typename U>
+    using FunctionReturnType = typename std::remove_reference<typename std::remove_cv<typename std::result_of<Func(U)>::type>::type>::type;
+#endif
 
 } // namespace Catch