diff -r 3d4e9c994f10 -r a86126ab1dd4 wp/wp-admin/includes/screen.php
--- a/wp/wp-admin/includes/screen.php	Tue Oct 22 16:11:46 2019 +0200
+++ b/wp/wp-admin/includes/screen.php	Tue Dec 15 13:49:49 2020 +0100
@@ -11,10 +11,8 @@
  *
  * @since 2.7.0
  *
- * @staticvar array $column_headers
- *
  * @param string|WP_Screen $screen The screen you want the headers for
- * @return array Containing the headers in the format id => UI String
+ * @return string[] The column header labels keyed by column ID.
  */
 function get_column_headers( $screen ) {
 	if ( is_string( $screen ) ) {
@@ -24,7 +22,6 @@
 	static $column_headers = array();
 
 	if ( ! isset( $column_headers[ $screen->id ] ) ) {
-
 		/**
 		 * Filters the column headers for a list table on a specific screen.
 		 *
@@ -35,7 +32,7 @@
 		 *
 		 * @since 3.0.0
 		 *
-		 * @param array $columns An array of column headers. Default empty.
+		 * @param string[] $columns The column header labels keyed by column ID.
 		 */
 		$column_headers[ $screen->id ] = apply_filters( "manage_{$screen->id}_columns", array() );
 	}
@@ -49,7 +46,7 @@
  * @since 2.7.0
  *
  * @param string|WP_Screen $screen The screen you want the hidden columns for
- * @return array
+ * @return string[] Array of IDs of hidden columns.
  */
 function get_hidden_columns( $screen ) {
 	if ( is_string( $screen ) ) {
@@ -68,7 +65,7 @@
 		 *
 		 * @since 4.4.0
 		 *
-		 * @param array     $hidden An array of columns hidden by default.
+		 * @param string[]  $hidden Array of IDs of columns hidden by default.
 		 * @param WP_Screen $screen WP_Screen object of the current screen.
 		 */
 		$hidden = apply_filters( 'default_hidden_columns', $hidden, $screen );
@@ -80,8 +77,8 @@
 	 * @since 4.4.0
 	 * @since 4.4.1 Added the `use_defaults` parameter.
 	 *
-	 * @param array     $hidden An array of hidden columns.
-	 * @param WP_Screen $screen WP_Screen object of the current screen.
+	 * @param string[]  $hidden       Array of IDs of hidden columns.
+	 * @param WP_Screen $screen       WP_Screen object of the current screen.
 	 * @param bool      $use_defaults Whether to show the default columns.
 	 */
 	return apply_filters( 'hidden_columns', $hidden, $screen, $use_defaults );
@@ -118,8 +115,8 @@
 				if ( false == $box || ! $box['title'] ) {
 					continue;
 				}
-				// Submit box cannot be hidden
-				if ( 'submitdiv' == $box['id'] || 'linksubmitdiv' == $box['id'] ) {
+				// Submit box cannot be hidden.
+				if ( 'submitdiv' === $box['id'] || 'linksubmitdiv' === $box['id'] ) {
 					continue;
 				}
 
@@ -129,10 +126,12 @@
 					$widget_title = $box['args']['__widget_basename'];
 				}
 
+				$is_hidden = in_array( $box['id'], $hidden, true );
+
 				printf(
 					'<label for="%1$s-hide"><input class="hide-postbox-tog" name="%1$s-hide" type="checkbox" id="%1$s-hide" value="%1$s" %2$s />%3$s</label>',
 					esc_attr( $box['id'] ),
-					checked( in_array( $box['id'], $hidden ), false, false ),
+					checked( $is_hidden, false, false ),
 					$widget_title
 				);
 			}
@@ -141,12 +140,12 @@
 }
 
 /**
- * Get Hidden Meta Boxes
+ * Gets an array of IDs of hidden meta boxes.
  *
  * @since 2.7.0
  *
  * @param string|WP_Screen $screen Screen identifier
- * @return array Hidden Meta Boxes
+ * @return string[] IDs of hidden meta boxes.
  */
 function get_hidden_meta_boxes( $screen ) {
 	if ( is_string( $screen ) ) {
@@ -157,11 +156,11 @@
 
 	$use_defaults = ! is_array( $hidden );
 
-	// Hide slug boxes by default
+	// Hide slug boxes by default.
 	if ( $use_defaults ) {
 		$hidden = array();
-		if ( 'post' == $screen->base ) {
-			if ( 'post' == $screen->post_type || 'page' == $screen->post_type || 'attachment' == $screen->post_type ) {
+		if ( 'post' === $screen->base ) {
+			if ( in_array( $screen->post_type, array( 'post', 'page', 'attachment' ), true ) ) {
 				$hidden = array( 'slugdiv', 'trackbacksdiv', 'postcustom', 'postexcerpt', 'commentstatusdiv', 'commentsdiv', 'authordiv', 'revisionsdiv' );
 			} else {
 				$hidden = array( 'slugdiv' );
@@ -173,7 +172,7 @@
 		 *
 		 * @since 3.1.0
 		 *
-		 * @param array     $hidden An array of meta boxes hidden by default.
+		 * @param string[]  $hidden An array of IDs of meta boxes hidden by default.
 		 * @param WP_Screen $screen WP_Screen object of the current screen.
 		 */
 		$hidden = apply_filters( 'default_hidden_meta_boxes', $hidden, $screen );
@@ -184,7 +183,7 @@
 	 *
 	 * @since 3.3.0
 	 *
-	 * @param array     $hidden       An array of hidden meta boxes.
+	 * @param string[]  $hidden       An array of IDs of hidden meta boxes.
 	 * @param WP_Screen $screen       WP_Screen object of the current screen.
 	 * @param bool      $use_defaults Whether to show the default meta boxes.
 	 *                                Default true.
@@ -198,7 +197,7 @@
  * @since 3.1.0
  *
  * @param string $option An option name.
- * @param mixed $args Option-dependent arguments.
+ * @param mixed  $args   Option-dependent arguments.
  */
 function add_screen_option( $option, $args = array() ) {
 	$current_screen = get_current_screen();
@@ -215,7 +214,7 @@
  *
  * @since 3.1.0
  *
- * @global WP_Screen $current_screen
+ * @global WP_Screen $current_screen WordPress current screen object.
  *
  * @return WP_Screen|null Current screen object or null when screen not defined.
  */
@@ -234,8 +233,8 @@
  *
  * @since 3.0.0
  *
- * @param mixed $hook_name Optional. The hook name (also known as the hook suffix) used to determine the screen,
- *                         or an existing screen object.
+ * @param string|WP_Screen $hook_name Optional. The hook name (also known as the hook suffix) used to determine the screen,
+ *                                    or an existing screen object.
  */
 function set_current_screen( $hook_name = '' ) {
 	WP_Screen::get( $hook_name )->set_current_screen();