[PHP 8.4] Fixes for implicit nullability deprecation (#337)

Fixes all issues that emit deprecation notices on PHP 8.4 for implicit nullable parameter type declarations.

See:
 - [RFC](https://wiki.php.net/rfc/deprecate-implicitly-nullable-types)
 - [PHP 8.4: Implicitly nullable parameter declarations deprecated](https://php.watch/versions/8.4/implicitly-marking-parameter-type-nullable-deprecated)

Author: Ayesh

lib/Assert/Assert.php

@@ -42,7 +42,7 @@ abstract class Assert
      * The assertion chain can be stateful, that means be careful when you reuse
      * it. You should never pass around the chain.
      */
-    public static function that($value, $defaultMessage = null, string $defaultPropertyPath = null): AssertionChain
+    public static function that($value, $defaultMessage = null, ?string $defaultPropertyPath = null): AssertionChain
     {
         $assertionChain = new AssertionChain($value, $defaultMessage, $defaultPropertyPath);
 
@@ -55,7 +55,7 @@ public static function that($value, $defaultMessage = null, string $defaultPrope
      * @param mixed $values
      * @param string|callable|null $defaultMessage
      */
-    public static function thatAll($values, $defaultMessage = null, string $defaultPropertyPath = null): AssertionChain
+    public static function thatAll($values, $defaultMessage = null, ?string $defaultPropertyPath = null): AssertionChain
     {
         return static::that($values, $defaultMessage, $defaultPropertyPath)->all();
     }
@@ -66,7 +66,7 @@ public static function thatAll($values, $defaultMessage = null, string $defaultP
      * @param mixed $value
      * @param string|callable|null $defaultMessage
      */
-    public static function thatNullOr($value, $defaultMessage = null, string $defaultPropertyPath = null): AssertionChain
+    public static function thatNullOr($value, $defaultMessage = null, ?string $defaultPropertyPath = null): AssertionChain
     {
         return static::that($value, $defaultMessage, $defaultPropertyPath)->nullOr();
     }

lib/Assert/Assertion.php

@@ -151,7 +151,7 @@ class AssertionChain
      * @param mixed $value
      * @param string|callable|null $defaultMessage
      */
-    public function __construct($value, $defaultMessage = null, string $defaultPropertyPath = null)
+    public function __construct($value, $defaultMessage = null, ?string $defaultPropertyPath = null)
     {
         $this->value = $value;
         $this->defaultMessage = $defaultMessage;

lib/Assert/AssertionChain.php

@@ -31,7 +31,7 @@ class InvalidArgumentException extends \InvalidArgumentException implements Asse
      */
     private $constraints;
 
-    public function __construct($message, $code, string $propertyPath = null, $value = null, array $constraints = [])
+    public function __construct($message, $code, ?string $propertyPath = null, $value = null, array $constraints = [])
     {
         parent::__construct($message, $code);
 

lib/Assert/InvalidArgumentException.php

@@ -133,7 +133,7 @@ class LazyAssertion
      *
      * @return static
      */
-    public function that($value, string $propertyPath = null, $defaultMessage = null)
+    public function that($value, ?string $propertyPath = null, $defaultMessage = null)
     {
         $this->currentChainFailed = false;
         $this->thisChainTryAll = false;

lib/Assert/LazyAssertion.php

@@ -32,7 +32,7 @@
  * The assertion chain can be stateful, that means be careful when you reuse
  * it. You should never pass around the chain.
  */
-function that($value, $defaultMessage = null, string $defaultPropertyPath = null): AssertionChain
+function that($value, $defaultMessage = null, ?string $defaultPropertyPath = null): AssertionChain
 {
     return Assert::that($value, $defaultMessage, $defaultPropertyPath);
 }
@@ -44,7 +44,7 @@ function that($value, $defaultMessage = null, string $defaultPropertyPath = null
  * @param string|callable|null $defaultMessage
  * @param string $defaultPropertyPath
  */
-function thatAll($values, $defaultMessage = null, string $defaultPropertyPath = null): AssertionChain
+function thatAll($values, $defaultMessage = null, ?string $defaultPropertyPath = null): AssertionChain
 {
     return Assert::thatAll($values, $defaultMessage, $defaultPropertyPath);
 }
@@ -58,7 +58,7 @@ function thatAll($values, $defaultMessage = null, string $defaultPropertyPath =
  *
  * @deprecated In favour of Assert::thatNullOr($value, $defaultMessage = null, $defaultPropertyPath = null)
  */
-function thatNullOr($value, $defaultMessage = null, string $defaultPropertyPath = null): AssertionChain
+function thatNullOr($value, $defaultMessage = null, ?string $defaultPropertyPath = null): AssertionChain
 {
     return Assert::thatNullOr($value, $defaultMessage, $defaultPropertyPath);
 }

lib/Assert/functions.php

@@ -31,7 +31,7 @@ public static function getCalls()
         return self::$calls;
     }
 
-    public static function string($value, $message = null, string $propertyPath = null): bool
+    public static function string($value, $message = null, ?string $propertyPath = null): bool
     {
         self::$calls[] = ['string', $value];