[DowngradePhp80] Handle union implements method from interface on DowngradeUnionTypeDeclarationRector

rules-tests/DowngradePhp80/Rector/FunctionLike/DowngradeUnionTypeDeclarationRector/Fixture/override_from_interface.php.inc

@@ -0,0 +1,38 @@
+<?php
+
+namespace Rector\Tests\DowngradePhp80\Rector\FunctionLike\DowngradeUnionTypeDeclarationRector\Fixture;
+
+use Rector\Tests\DowngradePhp80\Rector\FunctionLike\DowngradeUnionTypeDeclarationRector\Source\Foo1;
+use Rector\Tests\DowngradePhp80\Rector\FunctionLike\DowngradeUnionTypeDeclarationRector\Source\Foo2;
+use Rector\Tests\DowngradePhp80\Rector\FunctionLike\DowngradeUnionTypeDeclarationRector\Source\SomeInterface;
+
+class OverrideFromInterface implements SomeInterface
+{
+    public function run(): Foo1|Foo2
+    {
+        return new Foo1();
+    }
+}
+
+?>
+-----
+<?php
+
+namespace Rector\Tests\DowngradePhp80\Rector\FunctionLike\DowngradeUnionTypeDeclarationRector\Fixture;
+
+use Rector\Tests\DowngradePhp80\Rector\FunctionLike\DowngradeUnionTypeDeclarationRector\Source\Foo1;
+use Rector\Tests\DowngradePhp80\Rector\FunctionLike\DowngradeUnionTypeDeclarationRector\Source\Foo2;
+use Rector\Tests\DowngradePhp80\Rector\FunctionLike\DowngradeUnionTypeDeclarationRector\Source\SomeInterface;
+
+class OverrideFromInterface implements SomeInterface
+{
+    /**
+     * @return \Rector\Tests\DowngradePhp80\Rector\FunctionLike\DowngradeUnionTypeDeclarationRector\Source\Foo1|\Rector\Tests\DowngradePhp80\Rector\FunctionLike\DowngradeUnionTypeDeclarationRector\Source\Foo2
+     */
+    public function run(): \Rector\Tests\DowngradePhp80\Rector\FunctionLike\DowngradeUnionTypeDeclarationRector\Source\FooInterface
+    {
+        return new Foo1();
+    }
+}
+
+?>

rules-tests/DowngradePhp80/Rector/FunctionLike/DowngradeUnionTypeDeclarationRector/Source/Foo1.php

@@ -0,0 +1,7 @@
+<?php
+
+namespace Rector\Tests\DowngradePhp80\Rector\FunctionLike\DowngradeUnionTypeDeclarationRector\Source;
+
+class Foo1 implements FooInterface
+{
+}

rules-tests/DowngradePhp80/Rector/FunctionLike/DowngradeUnionTypeDeclarationRector/Source/Foo2.php

@@ -0,0 +1,7 @@
+<?php
+
+namespace Rector\Tests\DowngradePhp80\Rector\FunctionLike\DowngradeUnionTypeDeclarationRector\Source;
+
+class Foo2 implements FooInterface
+{
+}

rules-tests/DowngradePhp80/Rector/FunctionLike/DowngradeUnionTypeDeclarationRector/Source/FooInterface.php

@@ -0,0 +1,7 @@
+<?php
+
+namespace Rector\Tests\DowngradePhp80\Rector\FunctionLike\DowngradeUnionTypeDeclarationRector\Source;
+
+interface FooInterface
+{
+}

rules-tests/DowngradePhp80/Rector/FunctionLike/DowngradeUnionTypeDeclarationRector/Source/SomeInterface.php

@@ -0,0 +1,8 @@
+<?php
+
+namespace Rector\Tests\DowngradePhp80\Rector\FunctionLike\DowngradeUnionTypeDeclarationRector\Source;
+
+interface SomeInterface
+{
+    public function run(): FooInterface;
+}

src/PhpDocDecorator/PhpDocFromTypeDeclarationDecorator.php

@@ -10,7 +10,9 @@
 use PhpParser\Node\Expr\Closure;
 use PhpParser\Node\Identifier;
 use PhpParser\Node\Name;
+use PhpParser\Node\Name\FullyQualified;
 use PhpParser\Node\Param;
+use PhpParser\Node\Stmt\ClassLike;
 use PhpParser\Node\Stmt\ClassMethod;
 use PhpParser\Node\Stmt\Function_;
 use PHPStan\PhpDocParser\Ast\PhpDoc\ReturnTagValueNode;
@@ -27,6 +29,7 @@
 use Rector\Php\PhpVersionProvider;
 use Rector\Php80\NodeAnalyzer\PhpAttributeAnalyzer;
 use Rector\PhpAttribute\NodeFactory\PhpAttributeGroupFactory;
+use Rector\PhpParser\AstResolver;
 use Rector\PHPStanStaticTypeMapper\Enum\TypeKind;
 use Rector\Reflection\ReflectionResolver;
 use Rector\StaticTypeMapper\StaticTypeMapper;
@@ -52,7 +55,8 @@ public function __construct(
         private readonly PhpAttributeGroupFactory $phpAttributeGroupFactory,
         private readonly ReflectionResolver $reflectionResolver,
         private readonly PhpAttributeAnalyzer $phpAttributeAnalyzer,
-        private readonly PhpVersionProvider $phpVersionProvider
+        private readonly PhpVersionProvider $phpVersionProvider,
+        private readonly AstResolver $astResolver,
     ) {
         $this->classMethodWillChangeReturnTypes = [
             // @todo how to make list complete? is the method list needed or can we use just class names?
@@ -96,6 +100,29 @@ public function decorateReturn(ClassMethod|Function_|Closure|ArrowFunction $func
             return;
         }
 
+        $ancestors = array_filter(
+            $classReflection->getAncestors(),
+            static fn (ClassReflection $ancestor): bool => $classReflection->getName() !== $ancestor->getName()
+        );
+
+        foreach ($ancestors as $ancestor) {
+            $classLike = $this->astResolver->resolveClassFromClassReflection($ancestor);
+            if (! $classLike instanceof ClassLike) {
+                continue;
+            }
+
+            $classMethod = $classLike->getMethod($functionLike->name->toString());
+            if (! $classMethod instanceof ClassMethod) {
+                continue;
+            }
+
+            $returnType = $classMethod->returnType;
+            if ($returnType instanceof Node && $returnType instanceof FullyQualified) {
+                $functionLike->returnType = new FullyQualified($returnType->toString());
+                break;
+            }
+        }
+
         if (! $this->isRequireReturnTypeWillChange($classReflection, $functionLike)) {
             return;
         }