Only use GeneratedId for upserts, not inserts

Identifiers generated for inserts will be returned from WriteBatch::insert()

docs/api/MongoDB/GeneratedId.php

@@ -4,7 +4,7 @@ namespace MongoDB;
 
 /**
  * Value object for a document identifier that was generated by the driver or
- * server during an insert or upsert operation, respectively.
+ * server during an upsert operation, respectively.
  */
 final class GeneratedId
 {

docs/api/MongoDB/WriteBatch.php

@@ -23,8 +23,11 @@ class WriteBatch implements Countable
     /**
      * Adds an insert operation to the batch
      *
+     * The document's "_id" will be returned (either from the provided document
+     * or a generated value from the driver).
+     *
      * @param array|object $document Operation/document to add to insert
-     * @return self
+     * @return mixed Document identifier
      */
     function insert($document) {
         /*** CEF ***/
@@ -48,7 +51,6 @@ class WriteBatch implements Countable
      * @param array|object $query         Update criteria
      * @param array|object $newObj        Update modifier or replacement document
      * @param array        $updateOptions Update options (e.g. "upsert")
-     * @return self
      */
     function update($query, $newObj, array $updateOptions = null)
     {
@@ -94,7 +96,6 @@ class WriteBatch implements Countable
      *
      * @param array|object $query         Deletion criteria
      * @param array        $deleteOptions Deletion options (e.g. "limit")
-     * @return self
      */
     function delete($query, array $deleteOptions = null)
     {

docs/api/MongoDB/WriteResult.php

@@ -10,20 +10,6 @@ namespace MongoDB;
  */
 final class WriteResult
 {
-    /**
-     * Returns the GeneratedIds for any inserted documents
-     *
-     * @return GeneratedId[]
-     */
-    public function getGeneratedIdsForInsert()
-    {
-        /* Return an array of identifiers generated by the driver for insert
-         * operations. Each GeneratedId has a batch index and the ID value.
-         *
-         * This supersedes the identifier-setting hack in the 1.x driver.
-         */
-    }
-
     /**
      * Returns the GeneratedIds for any upserted documents
      *