Bug 1365654 - Add a move constructor to HashTable::Enum r=luke

js/public/HashTable.h

@@ -1070,13 +1070,21 @@ class HashTable : private AllocPolicy
         bool rekeyed;
         bool removed;
 
-        /* Not copyable. */
+        // Enum is movable but not copyable.
         Enum(const Enum&) = delete;
         void operator=(const Enum&) = delete;
 
       public:
-        template<class Map> explicit
-        Enum(Map& map) : Range(map.all()), table_(map.impl), rekeyed(false), removed(false) {}
+        template<class Map>
+        explicit Enum(Map& map)
+          : Range(map.all()), table_(map.impl), rekeyed(false), removed(false) {}
+
+        MOZ_IMPLICIT Enum(Enum&& other)
+          : Range(other), table_(other.table_), rekeyed(other.rekeyed), removed(other.removed)
+        {
+            other.rekeyed = false;
+            other.removed = false;
+        }
 
         // Removes the |front()| element from the table, leaving |front()|
         // invalid until the next call to |popFront()|. For example:

js/src/jsapi-tests/testHashTable.cpp

@@ -6,6 +6,8 @@
 #include "js/Utility.h"
 #include "jsapi-tests/tests.h"
 
+#include "mozilla/Move.h"
+
 //#define FUZZ
 
 typedef js::HashMap<uint32_t, uint32_t, js::DefaultHasher<uint32_t>, js::SystemAllocPolicy> IntMap;
@@ -388,3 +390,45 @@ BEGIN_TEST(testHashMapLookupWithDefaultOOM)
 
 END_TEST(testHashMapLookupWithDefaultOOM)
 #endif // defined(DEBUG)
+
+BEGIN_TEST(testHashTableMovableEnum)
+{
+    CHECK(set.init());
+
+    // Exercise returning a hash table Enum object from a function.
+
+    CHECK(set.put(1));
+    for (auto e = enumerateSet(); !e.empty(); e.popFront())
+        e.removeFront();
+    CHECK(set.count() == 0);
+
+    // Test moving an Enum object explicitly.
+
+    CHECK(set.put(1));
+    CHECK(set.put(2));
+    CHECK(set.put(3));
+    CHECK(set.count() == 3);
+    {
+        auto e1 = IntSet::Enum(set);
+        CHECK(!e1.empty());
+        e1.removeFront();
+        e1.popFront();
+
+        auto e2 = mozilla::Move(e1);
+        CHECK(!e2.empty());
+        e2.removeFront();
+        e2.popFront();
+    }
+
+    CHECK(set.count() == 1);
+    return true;
+}
+
+IntSet set;
+
+IntSet::Enum enumerateSet()
+{
+    return IntSet::Enum(set);
+}
+
+END_TEST(testHashTableMovableEnum)