[TypeDeclaration] Skip generic on ReturnTypeDeclarationRector (#2469)

* Add failing test fixture for ReturnTypeDeclarationRector

# Failing Test for ReturnTypeDeclarationRector

The native return type is replaced by the generic type of the pdpdoc, which does not exist.

Based on https://getrector.org/demo/5a20665a-b61f-4923-8b9a-aa9cb5c3a8ea

* Rename failing test

* Add missing namespace

* Closes #2454 Fixes rectorphp/rector#7213

* re-trigger CI

Co-authored-by: François Poguet <francoispoguet@gmail.com>
Co-authored-by: François Poguet <francois.poguet@quarks.pro>

rules-tests/TypeDeclaration/Rector/FunctionLike/ReturnTypeDeclarationRector/Fixture/skip_generic.php.inc

@@ -0,0 +1,20 @@
+<?php
+
+namespace Rector\Tests\TypeDeclaration\Rector\FunctionLike\ReturnTypeDeclarationRector\Fixture;
+
+class SkipGeneric
+{
+    private readonly UseCaseBusInterface $useCaseBus;
+
+    /**
+     * @template T
+     *
+     * @param UseCaseInterface<T> $useCase
+     *
+     * @return T
+     */
+    protected function execute(UseCaseInterface $useCase): mixed
+    {
+        return $this->useCaseBus->execute($useCase);
+    }
+}

rules/TypeDeclaration/Rector/FunctionLike/ReturnTypeDeclarationRector.php

@@ -21,6 +21,7 @@
 use Rector\Core\ValueObject\PhpVersionFeature;
 use Rector\NodeTypeResolver\Node\AttributeKey;
 use Rector\PHPStanStaticTypeMapper\Enum\TypeKind;
+use Rector\StaticTypeMapper\ValueObject\Type\NonExistingObjectType;
 use Rector\TypeDeclaration\PhpDocParser\NonInformativeReturnTagRemover;
 use Rector\TypeDeclaration\PhpParserTypeAnalyzer;
 use Rector\TypeDeclaration\TypeAlreadyAddedChecker\ReturnTypeAlreadyAddedChecker;
@@ -109,7 +110,7 @@ public function refactor(Node $node): ?Node
             [ReturnTypeDeclarationReturnTypeInfererTypeInferer::class]
         );
 
-        if ($inferedReturnType instanceof MixedType) {
+        if ($inferedReturnType instanceof MixedType || $inferedReturnType instanceof NonExistingObjectType) {
             return null;
         }