Fix compilation errors

include/xrpl/json/json_value.h

@@ -701,7 +701,7 @@ to_json(ripple::Number const& number)
 struct to_json_fn
 {
     template <typename T>
-    constexpr Value
+    Value
     operator()(T&& t) const
     {
         return to_json(std::forward<T>(t));
@@ -711,12 +711,9 @@ struct to_json_fn
 template <typename T>
 struct static_const
 {
-    static constexpr T value{};
+    static constexpr T value = {};
 };
 
-template <typename T>
-constexpr T static_const<T>::value;
-
 }  // namespace detail
 
 namespace {

include/xrpl/protocol/STIssue.h

@@ -37,6 +37,7 @@ public:
     using value_type = Asset;
 
     STIssue() = default;
+    STIssue(STIssue const& rhs) = default;
 
     explicit STIssue(SerialIter& sit, SField const& name);
 

src/test/app/MPToken_test.cpp

@@ -22,7 +22,6 @@
 #include <test/jtx/xchain_bridge.h>
 #include <xrpl/protocol/Feature.h>
 #include <xrpl/protocol/jss.h>
-#include <format>
 
 namespace ripple {
 namespace test {