Add move constructor to generated union class. (#4167)

* Add move constructor to generated union class.

* Unused default

* Add generated code

samples/monster_generated.h

@@ -74,6 +74,8 @@ struct EquipmentUnion {
   flatbuffers::NativeTable *table;
 
   EquipmentUnion() : type(Equipment_NONE), table(nullptr) {}
+  EquipmentUnion(EquipmentUnion&& u):
+    type(std::move(u.type)), table(std::move(u.table)) {}
   EquipmentUnion(const EquipmentUnion &);
   EquipmentUnion &operator=(const EquipmentUnion &);
   ~EquipmentUnion() { Reset(); }

src/idl_gen_cpp.cpp

@@ -650,6 +650,8 @@ class CppGenerator : public BaseGenerator {
       code_ += "  flatbuffers::NativeTable *table;";
       code_ += "";
       code_ += "  {{NAME}}Union() : type({{NONE}}), table(nullptr) {}";
+      code_ += "  {{NAME}}Union({{NAME}}Union&& u):";
+      code_ += "    type(std::move(u.type)), table(std::move(u.table)) {}";
       code_ += "  {{NAME}}Union(const {{NAME}}Union &);";
       code_ += "  {{NAME}}Union &operator=(const {{NAME}}Union &);";
       code_ += "  ~{{NAME}}Union() { Reset(); }";

tests/monster_test_generated.h

@@ -103,6 +103,8 @@ struct AnyUnion {
   flatbuffers::NativeTable *table;
 
   AnyUnion() : type(Any_NONE), table(nullptr) {}
+  AnyUnion(AnyUnion&& u):
+    type(std::move(u.type)), table(std::move(u.table)) {}
   AnyUnion(const AnyUnion &);
   AnyUnion &operator=(const AnyUnion &);
   ~AnyUnion() { Reset(); }