From 0bff4f21d5d0fb0bd7cc723dc8174acdaf27ffb1 Mon Sep 17 00:00:00 2001
From: Ichthyostega <prg@ichthyostega.de>
Date: Mon, 17 Aug 2015 20:56:40 +0200
Subject: [PATCH] Record References: fix copy and assignment handling

not entirely sure about the design, but lets try this approach:
they can be "cloned" and likewise move-assigned, but we do not
allow the regular assignment, because this would enable to use
references like pointers (what we deliberately do not want)
---
 src/lib/diff/record.hpp                           | 15 ++++++++++++++-
 .../diff/generic-record-representation-test.cpp   |  3 ++-
 2 files changed, 16 insertions(+), 2 deletions(-)

diff --git a/src/lib/diff/record.hpp b/src/lib/diff/record.hpp
index 8cf3e3411..8531695f9 100644
--- a/src/lib/diff/record.hpp
+++ b/src/lib/diff/record.hpp
@@ -514,7 +514,20 @@ namespace diff{
       /** prevent moving into black hole */
       RecordRef(Target&&) = delete;
       
-      // standard copy operations acceptable
+      RecordRef(RecordRef const&)  = default;
+      RecordRef(RecordRef     &&)  = default;
+      
+      /** references can not be reassigned */
+      RecordRef& operator= (RecordRef const&)  = delete;
+      RecordRef& operator= (RecordRef      &)  = delete;
+      
+      /** assignment is not allowed, but moving is */
+      RecordRef&
+      operator= (RecordRef &&o)
+        {
+          std::swap(record_, o.record_);
+          return *this;
+        }
       
       
       explicit
diff --git a/tests/library/diff/generic-record-representation-test.cpp b/tests/library/diff/generic-record-representation-test.cpp
index 1eac8e22b..1c65a8c62 100644
--- a/tests/library/diff/generic-record-representation-test.cpp
+++ b/tests/library/diff/generic-record-representation-test.cpp
@@ -326,12 +326,13 @@ namespace test{
           CHECK ("🌰" == oor.getType());
           CHECK (oor.get("♄") == "saturn");
           
-          // are copyable and assignable
+          // are copyable but not reassignable
           RecordRef<string> r2 = ref;
           CHECK (r2);
           CHECK (r2.get() == ref.get());
           CHECK (!isSameObject (r2, ref));
           
+          // but references are move-assignable
           empty = std::move(r2);
           CHECK (empty);
           CHECK (!r2);