Feat: Add NullableTypeDeclarationFixer to standardize nullable declar…

…ation using `?` (part of #94)

ecs.php

@@ -89,6 +89,7 @@
 use PhpCsFixer\Fixer\Import\OrderedImportsFixer;
 use PhpCsFixer\Fixer\LanguageConstruct\DeclareEqualNormalizeFixer;
 use PhpCsFixer\Fixer\LanguageConstruct\IsNullFixer;
+use PhpCsFixer\Fixer\LanguageConstruct\NullableTypeDeclarationFixer;
 use PhpCsFixer\Fixer\LanguageConstruct\SingleSpaceAroundConstructFixer;
 use PhpCsFixer\Fixer\ListNotation\ListSyntaxFixer;
 use PhpCsFixer\Fixer\NamespaceNotation\BlankLinesBeforeNamespaceFixer;
@@ -310,6 +311,8 @@
             DeclareEqualNormalizeFixer::class,
             // Replaces `is_null($var)` expression with `null === $var`
             IsNullFixer::class,
+            // Nullable single type declaration should be standardised using question mark syntax.
+            NullableTypeDeclarationFixer::class,
             // Ensures a single space around language constructs.
             SingleSpaceAroundConstructFixer::class,
             // Namespace must not contain spacing, comments or PHPDoc.

tests/Integration/Fixtures/Basic.correct.php.inc

@@ -168,4 +168,7 @@ class Basic extends AbstractBasic implements InterfaceFromThisNamespace // Fully
             2,
         );
     }
+
+    // NullableTypeDeclarationFixer
+    public function withParameters(?string $nullableValue): void {}
 }

tests/Integration/Fixtures/Basic.wrong.php.inc

@@ -165,4 +165,8 @@ but should be heredoc instead';
             2
         );
     }
+
+    // NullableTypeDeclarationFixer
+    public function withParameters(null|string $nullableValue): void
+    {}
 }