Collections cannot contain Collections.

By having both the constructor and the setComponents checking
a white- and a blacklist for allowed types, we ensure that no
Collections can be added through these methods to the list of
components.

src/ol/geom/Collection.js

@@ -13,16 +13,65 @@ goog.require('ol.Projection');
  * @constructor
  */
 ol.geom.Collection = function(components) {
+    
+    /**
+     * @private
+     * @type {Array.<Function>}
+     */
+    this.typeBlacklist_ = [
+        ol.geom.Collection
+    ];
+    
+    /**
+     * @private
+     * @type {Array.<Function>}
+     */
+    this.typeWhitelist_ = [];
+    
     /**
      * @private
      * @type {Array.<ol.geom.Geometry>}
      */
-    this.components_ = components;
+    this.components_ = [];
     
+    if (arguments.length === 1 && goog.isDef(components)) {
+        this.setComponents(components);
+    }
 };
 
 goog.inherits(ol.geom.Collection, ol.geom.Geometry);
 
+/**
+ * Sets the list of disallowed types for the collection. 
+ * @param {Array.<Function>} typeBlacklist Array of constructors to disallow.
+ */
+ol.geom.Collection.prototype.setTypeBlacklist = function(typeBlacklist){
+    this.typeBlacklist_ = typeBlacklist;
+};
+/**
+ * Gets the list of disallowed types for the collection. 
+ * @return {Array.<Function>} Array of constructors to disallow.
+ */
+ol.geom.Collection.prototype.getTypeBlacklist = function(){
+    return this.typeBlacklist_;
+};
+
+/**
+ * Sets the list of always allowed types for the collection. 
+ * @param {Array.<Function>} typeWhitelist Array of constructors to allow.
+ */
+ol.geom.Collection.prototype.setTypeWhitelist = function(typeWhitelist){
+    this.typeWhitelist_ = typeWhitelist;
+};
+/**
+ * Gets the list of always allowed types for the collection. 
+ * @return {Array.<Function>} Array of constructors to allow.
+ */
+ol.geom.Collection.prototype.getTypeWhitelist = function(){
+    return this.typeWhitelist_;
+};
+
+
 /**
  * Sets the Collection's components.
  * 
@@ -38,7 +87,17 @@ ol.geom.Collection.prototype.getComponents = function() {
  * @param {Array.<ol.geom.Geometry>} components An array of components.
  */
 ol.geom.Collection.prototype.setComponents = function(components) {
-    this.components_ = components;
+    var allValidTypes = goog.array.every(
+        components, 
+        this.isAllowedComponent,
+        this
+    );
+    if (allValidTypes) {
+        this.components_ = components;
+    } else {
+        throw new Error('ol.geom.Collection: at least one component passed to '
+            + 'setComponents is not allowed.');
+    }
 };
 
 /**
@@ -48,7 +107,52 @@ ol.geom.Collection.prototype.setComponents = function(components) {
  * @param {number} index The index where to add.
  */
 ol.geom.Collection.prototype.addComponent = function(component, index) {
-    goog.array.insertAt(this.components_,component,index);
+    if (this.isAllowedComponent(component)) {
+        goog.array.insertAt(this.components_, component, index);
+    } else {
+        throw new Error("ol.geom.Collection: The component is not allowed " 
+            + "to be added.");
+    }
+};
+
+/**
+ * Checks whether the passed component is an instance of any of the constructors
+ * listed in the passed list.
+ * 
+ * @param {ol.geom.Geometry} component The component to check.
+ * @param {Array.<Function>} list The List of constructors to check the 
+ *     component against.
+ * 
+ * @return {boolean} Whether the passed component is an instance of any of the 
+ *     constructors listed in the passed list.
+ * 
+ * @private
+ */
+ol.geom.Collection.prototype.isOnList = function(component, list) {
+    var isOnList = !goog.array.every(list, function(listedConstr){
+        if (component instanceof listedConstr) {
+            return false;
+        } else {
+            return true;
+        }
+    });
+    return isOnList;
+};
+
+/**
+ * Checks whether the passed component is allowed according to the black and 
+ * whitelists.
+ * 
+ * @param {ol.geom.Geometry} component The component to check.
+ * @return {boolean} Whether the passed component is allowed as part of this
+ *     collection according to black- and whitelist.
+ */
+ol.geom.Collection.prototype.isAllowedComponent = function(component){
+    var whitelist = this.getTypeWhitelist(),
+        blacklist = this.getTypeBlacklist(),
+        isOnWhitelist = this.isOnList(component, whitelist),
+        isOnBlacklist = this.isOnList(component, blacklist);
+    return (isOnWhitelist || !isOnBlacklist);
 };
 
 /**