[TypeDeclaration] Add nullable return $this on ReturnUnionTypeRector

packages/PHPStanStaticTypeMapper/TypeMapper/StaticTypeMapper.php

@@ -4,6 +4,7 @@
 
 namespace Rector\PHPStanStaticTypeMapper\TypeMapper;
 
+use PHPStan\Type\ThisType;
 use PhpParser\Node;
 use PhpParser\Node\Name;
 use PHPStan\PhpDocParser\Ast\Type\TypeNode;
@@ -51,13 +52,19 @@ public function mapToPhpParserNode(Type $type, string $typeKind): ?Node
     {
         // special case, for autocomplete of return type
         if ($type instanceof SimpleStaticType) {
-            return new Name(ObjectReference::STATIC);
+            return $this->phpVersionProvider->isAtLeastPhpVersion(PhpVersionFeature::STATIC_RETURN_TYPE)
+                ? new Name(ObjectReference::STATIC)
+                : new Name(ObjectReference::SELF);
         }
 
         if ($type instanceof SelfStaticType) {
             return new Name(ObjectReference::SELF);
         }
 
+        if ($type instanceof ThisType) {
+            return new Name(ObjectReference::SELF);
+        }
+
         if ($this->phpVersionProvider->isAtLeastPhpVersion(PhpVersionFeature::STATIC_RETURN_TYPE)) {
             return new Name(ObjectReference::STATIC);
         }

rules-tests/TypeDeclaration/Rector/ClassMethod/ReturnUnionTypeRector/Fixture/nullable_return_this.php.inc

@@ -0,0 +1,35 @@
+<?php
+
+namespace Rector\Tests\TypeDeclaration\Rector\ClassMethod\ReturnUnionTypeRector\Fixture;
+
+final class NullableReturnThis
+{
+    public function run()
+    {
+        if (rand(0, 1)) {
+            return null;
+        }
+
+        return $this;
+    }
+}
+
+?>
+-----
+<?php
+
+namespace Rector\Tests\TypeDeclaration\Rector\ClassMethod\ReturnUnionTypeRector\Fixture;
+
+final class NullableReturnThis
+{
+    public function run(): ?self
+    {
+        if (rand(0, 1)) {
+            return null;
+        }
+
+        return $this;
+    }
+}
+
+?>

rules/TypeDeclaration/Rector/ClassMethod/AddParamTypeFromPropertyTypeRector.php

@@ -93,9 +93,11 @@ public function refactor(Node $node): ?ClassMethod
             if ($param->type instanceof Node) {
                 continue;
             }
+
             if ($param->variadic) {
                 continue;
             }
+
             if (! $this->paramTypeAddGuard->isLegal($param, $node)) {
                 continue;
             }