Added forward declaration header json_forward.hpp. Minimise build times.

src/json.hpp

@@ -29,6 +29,10 @@ SOFTWARE.
 #ifndef NLOHMANN_JSON_HPP
 #define NLOHMANN_JSON_HPP
 
+
+#include "json_forward.hpp" // Some forward declarations are re-used here.
+
+
 #include <algorithm> // all_of, copy, fill, find, for_each, generate_n, none_of, remove, reverse, transform
 #include <array> // array
 #include <cassert> // assert
@@ -124,21 +128,6 @@ SOFTWARE.
 */
 namespace nlohmann
 {
-template<typename = void, typename = void>
-struct adl_serializer;
-
-// forward declaration of basic_json (required to split the class)
-template<template<typename U, typename V, typename... Args> class ObjectType =
-         std::map,
-         template<typename U, typename... Args> class ArrayType = std::vector,
-         class StringType = std::string, class BooleanType = bool,
-         class NumberIntegerType = std::int64_t,
-         class NumberUnsignedType = std::uint64_t,
-         class NumberFloatType = double,
-         template<typename U> class AllocatorType = std::allocator,
-         template<typename T, typename SFINAE = void> class JSONSerializer =
-         adl_serializer>
-class basic_json;
 
 // Ugly macros to avoid uglier copy-paste when specializing basic_json
 // This is only temporary and will be removed in 3.0

src/json_forward.hpp

@@ -0,0 +1,65 @@
+/*
+    __ _____ _____ _____
+ __|  |   __|     |   | |  JSON for Modern C++
+|  |  |__   |  |  | | | |  version 2.1.1
+|_____|_____|_____|_|___|  https://github.com/nlohmann/json
+
+Licensed under the MIT License <http://opensource.org/licenses/MIT>.
+Copyright (c) 2013-2017 Niels Lohmann <http://nlohmann.me>.
+
+Permission is hereby  granted, free of charge, to any  person obtaining a copy
+of this software and associated  documentation files (the "Software"), to deal
+in the Software  without restriction, including without  limitation the rights
+to  use, copy,  modify, merge,  publish, distribute,  sublicense, and/or  sell
+copies  of  the Software,  and  to  permit persons  to  whom  the Software  is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE  IS PROVIDED "AS  IS", WITHOUT WARRANTY  OF ANY KIND,  EXPRESS OR
+IMPLIED,  INCLUDING BUT  NOT  LIMITED TO  THE  WARRANTIES OF  MERCHANTABILITY,
+FITNESS FOR  A PARTICULAR PURPOSE AND  NONINFRINGEMENT. IN NO EVENT  SHALL THE
+AUTHORS  OR COPYRIGHT  HOLDERS  BE  LIABLE FOR  ANY  CLAIM,  DAMAGES OR  OTHER
+LIABILITY, WHETHER IN AN ACTION OF  CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE  OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.
+*/
+
+#ifndef NLOHMANN_JSON_FORWARD_HPP
+#define NLOHMANN_JSON_FORWARD_HPP
+
+#include <cstdint> // std::int64_t, std::uint64_t ...
+#include <iosfwd> // std::allocator
+#include <map> // map
+#include <string> // std::string
+#include <vector> // std::vector
+
+
+namespace nlohmann
+{
+
+template<typename = void, typename = void>
+struct adl_serializer;
+
+// forward declaration of basic_json
+template<template<typename U, typename V, typename... Args> class ObjectType =
+         std::map,
+         template<typename U, typename... Args> class ArrayType = std::vector,
+         class StringType = std::string, class BooleanType = bool,
+         class NumberIntegerType = std::int64_t,
+         class NumberUnsignedType = std::uint64_t,
+         class NumberFloatType = double,
+         template<typename U> class AllocatorType = std::allocator,
+         template<typename T, typename SFINAE = void> class JSONSerializer =
+         adl_serializer>
+class basic_json;
+
+
+// nlohmann::json uses defaults of args of basic_json<>.
+using json = basic_json<>;
+
+} // End namespace 'nlohmann'
+
+
+#endif // End NLOHMANN_JSON_FORWARD_HPP