[TypeDeclaration] Add return self object support on ReturnTypeFromStr…

…ictFluentReturnRector (#4915)

rules-tests/TypeDeclaration/Rector/ClassMethod/ReturnTypeFromStrictFluentReturnRector/Fixture/return_self.php.inc

@@ -0,0 +1,37 @@
+<?php
+
+namespace Rector\Tests\TypeDeclaration\Rector\ClassMethod\ReturnTypeFromStrictFluentReturnRector\Fixture;
+
+final class ReturnSelf
+{
+    private $foo = 'bar';
+
+    public function test()
+    {
+        $obj = new self();
+        $obj->foo = 'foo';
+
+        return $obj;
+    }
+}
+
+?>
+-----
+<?php
+
+namespace Rector\Tests\TypeDeclaration\Rector\ClassMethod\ReturnTypeFromStrictFluentReturnRector\Fixture;
+
+final class ReturnSelf
+{
+    private $foo = 'bar';
+
+    public function test(): self
+    {
+        $obj = new self();
+        $obj->foo = 'foo';
+
+        return $obj;
+    }
+}
+
+?>

rules/TypeDeclaration/Rector/ClassMethod/ReturnTypeFromStrictFluentReturnRector.php

@@ -9,6 +9,7 @@
 use PhpParser\Node\Stmt\ClassMethod;
 use PHPStan\Analyser\Scope;
 use PHPStan\Reflection\ClassReflection;
+use PHPStan\Type\ObjectType;
 use PHPStan\Type\ThisType;
 use Rector\Core\Php\PhpVersionProvider;
 use Rector\Core\Rector\AbstractScopeAwareRector;
@@ -86,14 +87,18 @@ public function refactorWithScope(Node $node, Scope $scope): ?Node
             return null;
         }
 
-        $returnType = $this->returnTypeInferer->inferFunctionLike($node);
-
-        if (! $returnType instanceof ThisType) {
+        $classReflection = $this->reflectionResolver->resolveClassReflection($node);
+        if (! $classReflection instanceof ClassReflection) {
             return null;
         }
 
-        $classReflection = $this->reflectionResolver->resolveClassReflection($node);
-        if (! $classReflection instanceof ClassReflection) {
+        $returnType = $this->returnTypeInferer->inferFunctionLike($node);
+        if ($returnType instanceof ObjectType && $returnType->getClassName() === $classReflection->getName()) {
+            $node->returnType = new Name('self');
+            return $node;
+        }
+
+        if (! $returnType instanceof ThisType) {
             return null;
         }