Better handling of trying to configure already instantiated component

framework/yii/base/Module.php

@@ -546,11 +546,16 @@ abstract class Module extends Component
 	public function setComponents($components)
 	{
 		foreach ($components as $id => $component) {
+			if (isset($this->_components[$id]) && !($this->_components[$id] instanceof Object)) {
 				if (isset($this->_components[$id]['class']) && !isset($component['class'])) {
 					$component['class'] = $this->_components[$id]['class'];
 				}
 				$this->_components[$id] = $component;
 			}
+			else {
+				throw new Exception('Cannot set component "'.$id.'" that is already instantiated.');
+			}
+		}
 	}
 
 	/**