From c217baa367a65724808c5df9d157b9a22eb6f563 Mon Sep 17 00:00:00 2001
From: seelabs <scott.determan@yahoo.com>
Date: Fri, 22 Mar 2019 09:19:35 -0400
Subject: [PATCH] Enable C++17

---
 CMakeLists.txt                       |  3 +-
 src/ripple/basics/date.h             |  1 +
 src/ripple/basics/random.h           |  2 +-
 src/ripple/beast/cxx17/type_traits.h | 80 +++-------------------------
 src/test/jtx/Env.h                   |  8 +--
 5 files changed, 14 insertions(+), 80 deletions(-)

diff --git a/CMakeLists.txt b/CMakeLists.txt
index 9913d453be..a44435d36b 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -478,7 +478,8 @@ add_library (Ripple::common ALIAS common)
 link_libraries (Ripple::common)
 set_target_properties (common
   PROPERTIES INTERFACE_POSITION_INDEPENDENT_CODE ON)
-target_compile_features (common INTERFACE cxx_std_14)
+set(CMAKE_CXX_EXTENSIONS OFF)
+target_compile_features (common INTERFACE cxx_std_17)
 target_compile_definitions (common
   INTERFACE
     $<$<CONFIG:Debug>:DEBUG _DEBUG>
diff --git a/src/ripple/basics/date.h b/src/ripple/basics/date.h
index 537806cbb0..f769bb9ae6 100644
--- a/src/ripple/basics/date.h
+++ b/src/ripple/basics/date.h
@@ -30,6 +30,7 @@
 // been invented (that would involve another several millennia of evolution).
 // We did not mean to shout.
 
+#define HAS_STRING_VIEW 0
 #ifndef HAS_STRING_VIEW
 #  if __cplusplus >= 201703
 #    define HAS_STRING_VIEW 1
diff --git a/src/ripple/basics/random.h b/src/ripple/basics/random.h
index 82dd873b56..e075222960 100644
--- a/src/ripple/basics/random.h
+++ b/src/ripple/basics/random.h
@@ -51,7 +51,7 @@ namespace detail {
 // Determines if a type can be called like an Engine
 template <class Engine, class Result = typename Engine::result_type>
 using is_engine =
-    std::is_invocable<Engine, Result()>;
+    std::is_invocable_r<Result, Engine>;
 }
 
 /** Return the default random engine.
diff --git a/src/ripple/beast/cxx17/type_traits.h b/src/ripple/beast/cxx17/type_traits.h
index 95f42b1050..0dfeee45bd 100644
--- a/src/ripple/beast/cxx17/type_traits.h
+++ b/src/ripple/beast/cxx17/type_traits.h
@@ -24,82 +24,18 @@
 #include <type_traits>
 #include <utility>
 
+#if defined(_LIBCPP_VERSION) && _LIBCPP_VERSION < 6000
+
 namespace std {
 
-#ifndef _MSC_VER
+template <class _Ret, class _Fn, class... _Args>
+struct _LIBCPP_TEMPLATE_VIS is_invocable_r
+    : integral_constant<bool, __invokable_r<_Ret, _Fn, _Args...>::value>
+{
+};
 
-    #if ! __cpp_lib_void_t
-
-        template<class...>
-        using void_t = void;
-
-    #endif // ! __cpp_lib_void_t
-
-    #if ! __cpp_lib_bool_constant
-
-        template<bool B>
-        using bool_constant = std::integral_constant<bool, B>;
-
-    #endif // ! __cpp_lib_bool_constant
+}  // namespace std
 
 #endif
 
-// Ideas from Howard Hinnant
-//
-// Specializations of is_constructible for pair and tuple which
-// work around an apparent defect in the standard that causes well
-// formed expressions involving pairs or tuples of non default-constructible
-// types to generate compile errors.
-//
-template <class T, class U>
-struct is_constructible <pair <T, U>>
-    : integral_constant <bool,
-        is_default_constructible <T>::value &&
-        is_default_constructible <U>::value>
-{
-    explicit is_constructible() = default;
-};
-
-//------------------------------------------------------------------------------
-
-namespace detail {
-template<class R, class C, class ...A>
-auto
-is_invocable_test(C&& c, int, A&& ...a)
-        -> decltype(std::is_convertible<
-                    decltype(c(std::forward<A>(a)...)), R>::value ||
-                    std::is_same<R, void>::value,
-                    std::true_type());
-
-template<class R, class C, class ...A>
-std::false_type
-is_invocable_test(C&& c, long, A&& ...a);
-} // detail
-
-/** Metafunction returns `true` if F callable as R(A...)
-
-    Example:
-
-    @code
-    is_invocable<T, void(std::string)>
-    @endcode
-*/
-/** @{ */
-template<class C, class F>
-struct is_invocable : std::false_type
-{
-};
-
-template<class C, class R, class ...A>
-struct is_invocable<C, R(A...)>
-        : decltype(std::detail::is_invocable_test<R>(
-            std::declval<C>(), 1, std::declval<A>()...))
-{
-};
-/** @} */
-
-//------------------------------------------------------------------------------
-
-} // std
-
 #endif
diff --git a/src/test/jtx/Env.h b/src/test/jtx/Env.h
index 9fe44862f9..d72f00f543 100644
--- a/src/test/jtx/Env.h
+++ b/src/test/jtx/Env.h
@@ -673,9 +673,7 @@ protected:
     void
     invoke (STTx& stx, FN const&... fN)
     {
-        // Sean Parent for_each_argument trick (C++ fold expressions would be
-        // nice here)
-        (void)std::array<int, sizeof...(fN)>{{((fN(*this, stx)), 0)...}};
+        (fN(*this, stx),...);
     }
 
     // Invoke funclets on jt
@@ -683,9 +681,7 @@ protected:
     void
     invoke (JTx& jt, FN const&... fN)
     {
-        // Sean Parent for_each_argument trick (C++ fold expressions would be
-        // nice here)
-        (void)std::array<int, sizeof...(fN)>{{((fN(*this, jt)), 0)...}};
+        (fN(*this, jt),...);
     }
 
     // Map of account IDs to Account