@@ -7,9 +7,9 @@
 	public immutable int y, x;
 	mixin DeriveCreate;
 	mixin DeriveCompare;
 	mixin DeriveShow;
-	Pos clone() const { return new Pos(y, x); }
+	Pos clone() const { return cast(Pos) this; }
 
 @property:
 	Pos wait()  { return this.clone(); }
 	Pos up()    { return new Pos(y+1, x); }
@@ -44,9 +44,9 @@
 	public immutable int base, pace;
 	mixin DeriveCreate;
 	mixin DeriveCompare;
 	mixin DeriveShow;
-	Water clone() const { return new Water(base, pace); }
+	Water clone() const { return cast(Water)this; }
 
 	static load(string[string] params)
 	{
 		return new Water(
@@ -103,9 +103,9 @@
 	Pos lift;
 	int waterproof;
 
 	Map clone() const { return new Map(this); }
-	this(const(Map) m) {
+	this(in Map m) {
 		foreach(s; m.data)
 			this.data ~= s.dup;
 		this.robot = m.robot.clone();
 		this.lift = m.lift.clone();
@@ -305,9 +305,9 @@
 		this.water = Water.load(params);
 	}
 
 	Game clone() const { return new Game(this); }
-	this(const(Game) g) {
+	this(in Game g) {
 		map = g.map.clone();
 		water = g.water.clone();
 		turn = g.turn;
 		dead = g.dead;