[Bug libstdc++/118842] `std::result_of` and `std::result_of_t` should be removed in C++20

[redi at gcc dot gnu.org via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=118842

--- Comment #2 from Jonathan Wakely <redi at gcc dot gnu.org> ---
--- a/libstdc++-v3/include/std/type_traits
+++ b/libstdc++-v3/include/std/type_traits
@@ -2616,7 +2616,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION

   /// result_of
   template<typename _Signature>
-    struct result_of;
+    struct _GLIBCXX17_DEPRECATED_SUGGEST("std::invoke_result") result_of;

   // Sfinae-friendly result_of implementation:

@@ -2813,7 +2813,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
   template<typename _Functor, typename... _ArgTypes>
     struct result_of<_Functor(_ArgTypes...)>
     : public __invoke_result<_Functor, _ArgTypes...>
-    { } _GLIBCXX17_DEPRECATED_SUGGEST("std::invoke_result");
+    { };

 #if __cplusplus >= 201402L
 #pragma GCC diagnostic push