https://bugs.gentoo.org/914583
https://github.com/Tencent/rapidjson/commit/3b2441b87f99ab65f37b141a7b548ebadb607b96
https://github.com/Tencent/rapidjson/issues/718

From 3b2441b87f99ab65f37b141a7b548ebadb607b96 Mon Sep 17 00:00:00 2001
From: Janusz Chorko <janusz.chorko@apdu.pl>
Date: Fri, 26 Aug 2016 21:17:38 +0200
Subject: [PATCH] Removed non-compiling assignment operator. Fixed #718

--- a/include/rapidjson/document.h
+++ b/include/rapidjson/document.h
@@ -316,8 +316,6 @@ struct GenericStringRef {
 
     GenericStringRef(const GenericStringRef& rhs) : s(rhs.s), length(rhs.length) {}
 
-    GenericStringRef& operator=(const GenericStringRef& rhs) { s = rhs.s; length = rhs.length; }
-
     //! implicit conversion to plain CharType pointer
     operator const Ch *() const { return s; }