move operator<< overloads to corresponding headers

include/boost/json/array.hpp

@@ -1659,6 +1659,30 @@ public:
         return ! (lhs == rhs);
     }
 
+    /** Serialize @ref array to an output stream.
+
+        This function serializes an `array` as JSON into the output stream.
+
+        @return Reference to `os`.
+
+        @par Complexity
+        Constant or linear in the size of `arr`.
+
+        @par Exception Safety
+        Strong guarantee.
+        Calls to `memory_resource::allocate` may throw.
+
+        @param os The output stream to serialize to.
+
+        @param arr The value to serialize.
+    */
+    BOOST_JSON_DECL
+    friend
+    std::ostream&
+    operator<<(
+        std::ostream& os,
+        array const& arr);
+
 private:
     template<class It>
     using iter_cat = typename

include/boost/json/object.hpp

@@ -1529,6 +1529,29 @@ public:
         return ! (lhs == rhs);
     }
 
+    /** Serialize @ref object to an output stream.
+
+        This function serializes an `object` as JSON into the output stream.
+
+        @return Reference to `os`.
+
+        @par Complexity
+        Constant or linear in the size of `obj`.
+
+        @par Exception Safety
+        Strong guarantee.
+        Calls to `memory_resource::allocate` may throw.
+
+        @param os The output stream to serialize to.
+
+        @param obj The value to serialize.
+    */
+    BOOST_JSON_DECL
+    friend
+    std::ostream&
+    operator<<(
+        std::ostream& os,
+        object const& obj);
 private:
 #ifndef BOOST_JSON_DOCS
     // VFALCO friending a detail function makes it public

include/boost/json/serialize.hpp

@@ -55,50 +55,6 @@ std::string
 serialize(string_view t);
 /** @} */
 
-/** Serialize an element to an output stream.
-
-    This function serializes the specified element
-    as JSON into the output stream.
-
-    @return `os`.
-
-    @par Complexity
-    Constant or linear in the size of `t`.
-
-    @par Exception Safety
-    Strong guarantee.
-    Calls to `memory_resource::allocate` may throw.
-
-    @param os The output stream to serialize to.
-
-    @param t The value to serialize
-*/
-/** @{ */
-BOOST_JSON_DECL
-std::ostream&
-operator<<(
-    std::ostream& os,
-    value const& t);
-
-BOOST_JSON_DECL
-std::ostream&
-operator<<(
-    std::ostream& os,
-    array const& t);
-
-BOOST_JSON_DECL
-std::ostream&
-operator<<(
-    std::ostream& os,
-    object const& t);
-
-BOOST_JSON_DECL
-std::ostream&
-operator<<(
-    std::ostream& os,
-    string const& t);
-/** @} */
-
 BOOST_JSON_NS_END
 
 #endif

include/boost/json/string.hpp

@@ -2738,6 +2738,30 @@ public:
         return subview().find_last_not_of(ch, pos);
     }
 
+    /** Serialize @ref string to an output stream.
+
+        This function serializes a `string` as JSON into the output stream.
+
+        @return Reference to `os`.
+
+        @par Complexity
+        Constant or linear in the size of `str`.
+
+        @par Exception Safety
+        Strong guarantee.
+        Calls to `memory_resource::allocate` may throw.
+
+        @param os The output stream to serialize to.
+
+        @param str The value to serialize.
+    */
+    BOOST_JSON_DECL
+    friend
+    std::ostream&
+    operator<<(
+        std::ostream& os,
+        string const& str);
+
 private:
     class undo;
 

include/boost/json/value.hpp

@@ -3315,6 +3315,30 @@ public:
         return ! (lhs == rhs);
     }
 
+    /** Serialize @ref value to an output stream.
+
+        This function serializes a `value` as JSON into the output stream.
+
+        @return Reference to `os`.
+
+        @par Complexity
+        Constant or linear in the size of `jv`.
+
+        @par Exception Safety
+        Strong guarantee.
+        Calls to `memory_resource::allocate` may throw.
+
+        @param os The output stream to serialize to.
+
+        @param jv The value to serialize.
+    */
+    BOOST_JSON_DECL
+    friend
+    std::ostream&
+    operator<<(
+        std::ostream& os,
+        value const& jv);
+
 private:
     static
     void