1 files changed, 33 insertions, 2 deletions

diff --git a/tools/editor/scene_tree_dock.cpp b/tools/editor/scene_tree_dock.cpp
index cff3913579..2012d96664 100644
--- a/tools/editor/scene_tree_dock.cpp
+++ b/tools/editor/scene_tree_dock.cpp
@@ -79,10 +79,22 @@ Node* SceneTreeDock::instance(const String& p_file) {
 		//accept->get_cancel()->hide();
 		accept->get_ok()->set_text("Ugh");
 		accept->set_text(String("Error loading scene from ")+p_file);
-		accept->popup_centered(Size2(300,70));;
+		accept->popup_centered(Size2(300,70));
 		return NULL;
 	}
 
+	// If the scene hasn't been saved yet a cyclical dependency cannot exist.
+	if (edited_scene->get_filename()!="") {
+
+		if (_cyclical_dependency_exists(edited_scene->get_filename(), instanced_scene)) {
+
+			accept->get_ok()->set_text("Ok");
+			accept->set_text(String("Cannot instance the scene '")+p_file+String("' because the current scene exists within one of its' nodes."));
+			accept->popup_centered(Size2(300,90));
+			return NULL;
+		}
+	}
+
 	instanced_scene->generate_instance_state();
 	instanced_scene->set_filename( Globals::get_singleton()->localize_path(p_file) );
 
@@ -100,6 +112,25 @@ Node* SceneTreeDock::instance(const String& p_file) {
 
 }
 
+bool SceneTreeDock::_cyclical_dependency_exists(const String& p_target_scene_path, Node* p_desired_node) {
+	int childCount = p_desired_node->get_child_count();
+
+	if (p_desired_node->get_filename()==p_target_scene_path) {
+		return true;
+	}
+
+	for (int i=0;i<childCount;i++) {
+		Node* child=p_desired_node->get_child(i);
+
+		if(_cyclical_dependency_exists(p_target_scene_path,child)) {
+			return true;
+		}
+	}
+
+	return false;
+}
+
+
 static String _get_name_num_separator() {
 	switch(EditorSettings::get_singleton()->get("scenetree_editor/duplicate_node_name_num_separator").operator int()) {
 		case 0: return "";
@@ -1223,7 +1254,7 @@ SceneTreeDock::SceneTreeDock(EditorNode *p_editor,Node *p_scene_root,EditorSelec
 
 	tb = memnew( ToolButton );
 	tb->connect("pressed",this,"_tool_selected",make_binds(TOOL_INSTANCE, false));
-	tb->set_tooltip("Instance a Node from scene file.");
+	tb->set_tooltip("Instance a scene file as a Node.");
 	hbc_top->add_child(tb);
 	tool_buttons[TOOL_INSTANCE]=tb;