diff --git a/wp-admin/includes/screen.php b/wp-admin/includes/screen.php
index 0482d783e0..ea96050b3d 100644
--- a/wp-admin/includes/screen.php
+++ b/wp-admin/includes/screen.php
@@ -368,7 +368,7 @@ final class WP_Screen {
 	 * @since 3.3.0
 	 * @access public
 	 *
-	 * @param string $hook_name Optional. The hook name (also known as the hook suffix) used to determine the screen.
+	 * @param string|WP_Screen $hook_name Optional. The hook name (also known as the hook suffix) used to determine the screen.
 	 * 	Defaults to the current $hook_suffix global.
 	 * @return WP_Screen Screen object.
 	 */
diff --git a/wp-includes/capabilities.php b/wp-includes/capabilities.php
index 894a149e3d..e52f61817a 100644
--- a/wp-includes/capabilities.php
+++ b/wp-includes/capabilities.php
@@ -550,7 +550,7 @@ class WP_User {
 	 *
 	 * @param string $field The field to query against: 'id', 'slug', 'email' or 'login'
 	 * @param string|int $value The field value
-	 * @return object Raw user object
+	 * @return object|false Raw user object
 	 */
 	public static function get_data_by( $field, $value ) {
 		global $wpdb;
diff --git a/wp-includes/class-wp-embed.php b/wp-includes/class-wp-embed.php
index a10024a789..8a64624c13 100644
--- a/wp-includes/class-wp-embed.php
+++ b/wp-includes/class-wp-embed.php
@@ -126,7 +126,8 @@ class WP_Embed {
 	 *     @type int $height Height of the embed in pixels.
 	 * }
 	 * @param string $url The URL attempting to be embedded.
-	 * @return string The embed HTML on success, otherwise the original URL.
+	 * @return string|false The embed HTML on success, otherwise the original URL.
+	 *                      `->maybe_make_link()` can return false on failure.
 	 */
 	public function shortcode( $attr, $url = '' ) {
 		$post = get_post();
diff --git a/wp-includes/class-wp-image-editor-imagick.php b/wp-includes/class-wp-image-editor-imagick.php
index 843b85c541..d51ea8e334 100644
--- a/wp-includes/class-wp-image-editor-imagick.php
+++ b/wp-includes/class-wp-image-editor-imagick.php
@@ -190,6 +190,8 @@ class WP_Image_Editor_Imagick extends WP_Image_Editor {
 	 *
 	 * @param int $width
 	 * @param int $height
+	 *
+	 * @return true|WP_Error
 	 */
 	protected function update_size( $width = null, $height = null ) {
 		$size = null;
diff --git a/wp-includes/class-wp-image-editor.php b/wp-includes/class-wp-image-editor.php
index fcca5574b8..0eb14aebb8 100644
--- a/wp-includes/class-wp-image-editor.php
+++ b/wp-includes/class-wp-image-editor.php
@@ -194,6 +194,7 @@ abstract class WP_Image_Editor {
 	 *
 	 * @param int $width
 	 * @param int $height
+	 * @return true
 	 */
 	protected function update_size( $width = null, $height = null ) {
 		$this->size = array(
@@ -388,7 +389,7 @@ abstract class WP_Image_Editor {
 	 * @since 3.5.0
 	 * @access public
 	 *
-	 * @return string suffix
+	 * @return false|string suffix
 	 */
 	public function get_suffix() {
 		if ( ! $this->get_size() )
diff --git a/wp-includes/meta.php b/wp-includes/meta.php
index 1637413d78..da465d064c 100644
--- a/wp-includes/meta.php
+++ b/wp-includes/meta.php
@@ -1146,8 +1146,6 @@ class WP_Meta_Query {
 	 * }
 	 */
 	public function get_sql( $type, $primary_table, $primary_id_column, $context = null ) {
-		global $wpdb;
-
 		if ( ! $meta_table = _get_meta_table( $type ) ) {
 			return false;
 		}