Remove use of beast::detail::is_invocable trait

src/ripple/basics/random.h

@@ -22,7 +22,6 @@
 
 #include <ripple/basics/win32_workaround.h>
 #include <ripple/beast/xor_shift_engine.h>
-#include <boost/beast/core/detail/type_traits.hpp>
 #include <boost/thread/tss.hpp>
 #include <cassert>
 #include <cstddef>
@@ -30,7 +29,7 @@
 #include <cstring>
 #include <random>
 #include <limits>
-#include <type_traits>
+#include <ripple/beast/cxx17/type_traits.h> // <type_traits>
 
 namespace ripple {
 
@@ -52,7 +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 =
-    boost::beast::detail::is_invocable<Engine, Result()>;
+    std::is_invocable<Engine, Result()>;
 }
 
 /** Return the default random engine.

src/ripple/beast/cxx17/type_traits.h

@@ -60,6 +60,46 @@ struct is_constructible <pair <T, U>>
     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

src/test/jtx/Env.h

@@ -45,11 +45,10 @@
 #include <ripple/protocol/STAmount.h>
 #include <ripple/protocol/STObject.h>
 #include <ripple/protocol/STTx.h>
-#include <boost/beast/core/detail/type_traits.hpp>
 #include <functional>
 #include <string>
 #include <tuple>
-#include <type_traits>
+#include <ripple/beast/cxx17/type_traits.h> // <type_traits>
 #include <utility>
 #include <unordered_map>
 #include <vector>
@@ -691,7 +690,7 @@ protected:
         FN const&... fN)
     {
         maybe_invoke(stx, f,
-            boost::beast::detail::is_invocable<F,
+            std::is_invocable<F,
                 void(Env&, STTx const&)>());
         invoke(stx, fN...);
     }
@@ -725,7 +724,7 @@ protected:
         FN const&... fN)
     {
         maybe_invoke(jt, f,
-            boost::beast::detail::is_invocable<F,
+            std::is_invocable<F,
                 void(Env&, JTx&)>());
         invoke(jt, fN...);
     }