lib: Use type declaration on undocumented private functions

Change-Id: Ieee119e678d8993ea15a8fd9efb4a301375d0c3a

Author: umherirrender

src/Diff/Internal/SiteLinkListPatcher.php

@@ -71,7 +71,7 @@ static function( $idSerialization ) {
 		);
 	}
 
-	private function getSiteLinksInDiffFormat( SiteLinkList $siteLinks ) {
+	private function getSiteLinksInDiffFormat( SiteLinkList $siteLinks ): array {
 		$linksInDiffFormat = [];
 
 		foreach ( $siteLinks->toArray() as $siteLink ) {

src/Diff/ItemDiffer.php

@@ -72,7 +72,7 @@ public function diffItems( Item $from, Item $to ) {
 		return new ItemDiff( $diffOps );
 	}
 
-	private function toDiffArray( Item $item ) {
+	private function toDiffArray( Item $item ): array {
 		$array = [];
 
 		$array['aliases'] = $item->getAliasGroups()->toTextArray();
@@ -83,7 +83,7 @@ private function toDiffArray( Item $item ) {
 		return $array;
 	}
 
-	private function getSiteLinksInDiffFormat( SiteLinkList $siteLinks ) {
+	private function getSiteLinksInDiffFormat( SiteLinkList $siteLinks ): array {
 		$linksInDiffFormat = [];
 
 		foreach ( $siteLinks->toArray() as $siteLink ) {

src/Diff/StatementListDiffer.php

@@ -40,7 +40,7 @@ private function newDiffer() {
 		return new MapDiffer( false, null, new ComparableComparer() );
 	}
 
-	private function toDiffArray( StatementList $statementList ) {
+	private function toDiffArray( StatementList $statementList ): array {
 		$statementArray = [];
 
 		/**