Cache.replaceRemovedItem

Called when a cache element is removed, replaces the cache items at index "replaced" with the one at index "replace" by swapping the items.

Unlike all other situations where indices and are used, "replaced" and "replace" must be always valid, i.e. less than length.

Note: A subclass may erase removed elements by overriding this method as follows:

protected override hash_t replaceRemovedItem ( size_t replaced,
                                               size_t replace )
{
    scope (success) this.items[replace] = this.items[replace].init;

    return (this.items[replaced] = this.items[replace]).key;
}