Util: Move staticConst<T> to separate header

src/util/json/conversion.h

@@ -0,0 +1,22 @@
+/*
+ * Copyright (C) 2022 Riyyi
+ *
+ * SPDX-License-Identifier: MIT
+ */
+
+#ifndef JSON_CONVERSION_H
+#define JSON_CONVERSION_H
+
+namespace Json {
+
+namespace Detail {
+
+// Avoid ODR (One Definition Rule) violations
+template<typename T>
+constexpr T staticConst {};
+
+} // namespace Detail
+
+} // namespace Json
+
+#endif // JSON_CONVERSION_H

src/util/json/fromjson.h

@@ -13,9 +13,11 @@
 #include <map>
 #include <string>
 #include <unordered_map>
+#include <utility> // forward
 #include <vector>
 
 #include "util/json/array.h"
+#include "util/json/conversion.h"
 #include "util/json/object.h"
 
 namespace Json {
@@ -86,10 +88,6 @@ struct fromJsonFunction {
 	}
 };
 
-// Avoid ODR (One Definition Rule) violations
-template<typename T>
-constexpr T staticConst {};
-
 } // namespace Detail
 
 // Anonymous namespace prevents multiple definition of the reference