Prevent 'Change Type' on nodes from an instanced scene

(cherry picked from commit e28cc34db89f390106fbb745e296055bcabc237f)

editor/scene_tree_dock.cpp

@@ -521,6 +521,14 @@ void SceneTreeDock::_tool_selected(int p_tool, bool p_confirm_override) {
 				break;
 			}
 
+			if (!_validate_no_foreign()) {
+				break;
+			}
+
+			if (!_validate_no_instance()) {
+				break;
+			}
+
 			Node *selected = scene_tree->get_selected();
 			if (!selected && !editor_selection->get_selected_node_list().empty())
 				selected = editor_selection->get_selected_node_list().front()->get();
@@ -1635,6 +1643,20 @@ bool SceneTreeDock::_validate_no_foreign() {
 	return true;
 }
 
+bool SceneTreeDock::_validate_no_instance() {
+	List<Node *> selection = editor_selection->get_selected_node_list();
+
+	for (List<Node *>::Element *E = selection.front(); E; E = E->next()) {
+		if (E->get() != edited_scene && E->get()->get_filename() != "") {
+			accept->set_text(TTR("This operation can't be done on instanced scenes."));
+			accept->popup_centered();
+			return false;
+		}
+	}
+
+	return true;
+}
+
 void SceneTreeDock::_node_reparent(NodePath p_path, bool p_keep_global_xform) {
 
 	Node *new_parent = scene_root->get_node(p_path);
@@ -2632,7 +2654,18 @@ void SceneTreeDock::_tree_rmb(const Vector2 &p_menu_pos) {
 		if (full_selection.size() == 1) {
 			menu->add_icon_shortcut(get_icon("Rename", "EditorIcons"), ED_GET_SHORTCUT("scene_tree/rename"), TOOL_RENAME);
 		}
-		menu->add_icon_shortcut(get_icon("Reload", "EditorIcons"), ED_GET_SHORTCUT("scene_tree/change_node_type"), TOOL_REPLACE);
+
+		bool can_replace = true;
+		for (List<Node *>::Element *E = selection.front(); E; E = E->next()) {
+			if (E->get() != edited_scene && (E->get()->get_owner() != edited_scene || E->get()->get_filename() != "")) {
+				can_replace = false;
+				break;
+			}
+		}
+
+		if (can_replace) {
+			menu->add_icon_shortcut(get_icon("Reload", "EditorIcons"), ED_GET_SHORTCUT("scene_tree/change_node_type"), TOOL_REPLACE);
+		}
 
 		if (scene_tree->get_selected() != edited_scene) {
 			menu->add_separator();

editor/scene_tree_dock.h

@@ -211,6 +211,7 @@ class SceneTreeDock : public VBoxContainer {
 	void _new_scene_from(String p_file);
 
 	bool _validate_no_foreign();
+	bool _validate_no_instance();
 	void _selection_changed();
 	void _update_script_button();
 	Node *_get_selection_group_tail(Node *p_node, List<Node *> p_list);