Source Reference:

• Component: bbPress:: bbp-topic

  File: /bbp-includes/bbp-topic-functions.php :: Trac Source Line: 2401

  	// Get topic
  	if ( !$topic = wp_get_single_post( $topic_id, ARRAY_A ) )
  		return $topic;
  
  	// Bail if already closed
  	if ( bbp_get_closed_status_id == $topic['post_status'] )
  		return false;
  
  	// Execute pre close code
  	do_action( 'bbp_close_topic', $topic_id );
  
  	// Add pre close status
  	add_post_meta( $topic_id, '_bbp_status', $topic['post_status'] );
  
  	// Set closed status
  	$topic['post_status'] = bbp_get_closed_status_id();
  
  	// No revisions
  	remove_action( 'pre_post_update', 'wp_save_post_revision' );