Do not use implicitly nullable parameters and prepare release

ChangeLog.md

@@ -2,6 +2,12 @@
 
 All notable changes are documented in this file using the [Keep a CHANGELOG](http://keepachangelog.com/) principles.
 
+## [5.1.1] - 2024-03-02
+
+### Changed
+
+* Do not use implicitly nullable parameters
+
 ## [5.1.0] - 2023-12-22
 
 ### Added
@@ -124,6 +130,7 @@ All notable changes are documented in this file using the [Keep a CHANGELOG](htt
 
 * This component is no longer supported on PHP 5.6
 
+[5.1.1]: https://github.com/sebastianbergmann/diff/compare/5.1.0...5.1.1
 [5.1.0]: https://github.com/sebastianbergmann/diff/compare/5.0.3...5.1.0
 [5.0.3]: https://github.com/sebastianbergmann/diff/compare/5.0.2...5.0.3
 [5.0.2]: https://github.com/sebastianbergmann/diff/compare/5.0.1...5.0.2

src/Differ.php

@@ -42,14 +42,14 @@ public function __construct(DiffOutputBuilderInterface $outputBuilder)
         $this->outputBuilder = $outputBuilder;
     }
 
-    public function diff(array|string $from, array|string $to, LongestCommonSubsequenceCalculator $lcs = null): string
+    public function diff(array|string $from, array|string $to, ?LongestCommonSubsequenceCalculator $lcs = null): string
     {
         $diff = $this->diffToArray($from, $to, $lcs);
 
         return $this->outputBuilder->getDiff($diff);
     }
 
-    public function diffToArray(array|string $from, array|string $to, LongestCommonSubsequenceCalculator $lcs = null): array
+    public function diffToArray(array|string $from, array|string $to, ?LongestCommonSubsequenceCalculator $lcs = null): array
     {
         if (is_string($from)) {
             $from = $this->splitStringByLines($from);

src/Exception/ConfigurationException.php

@@ -21,7 +21,7 @@ public function __construct(
         string $expected,
         $value,
         int $code = 0,
-        Exception $previous = null
+        ?Exception $previous = null
     ) {
         parent::__construct(
             sprintf(