[CodeQuality] Skip union types in AssertEqualsToSameRector to preserve loose type comparison

rules-tests/CodeQuality/Rector/MethodCall/AssertEqualsToSameRector/Fixture/skip_union_type.php.inc

@@ -0,0 +1,18 @@
+<?php
+
+namespace Rector\PHPUnit\Tests\CodeQuality\Rector\MethodCall\AssertEqualsToSameRector\Fixture;
+
+use PHPUnit\Framework\TestCase;
+
+final class SkipUnionType extends TestCase
+{
+    public function test(string|int|bool|\DateTime $expected)
+    {
+        $this->assertEquals('value', $this->normalizeStringValue($expected));
+    }
+
+    private function normalizeStringValue(string|int|bool|\DateTime $input): string|int|bool|\DateTime
+    {
+        return $input;
+    }
+}

rules/CodeQuality/Rector/MethodCall/AssertEqualsToSameRector.php

@@ -23,6 +23,7 @@
 use PHPStan\Type\StringType;
 use PHPStan\Type\Type;
 use PHPStan\Type\TypeCombinator;
+use PHPStan\Type\UnionType;
 use Rector\PHPUnit\NodeAnalyzer\IdentifierManipulator;
 use Rector\PHPUnit\NodeAnalyzer\TestsNodeAnalyzer;
 use Rector\Rector\AbstractRector;
@@ -126,6 +127,11 @@ private function shouldSkipLooseComparison(array $args): bool
         $firstArgType = $this->nodeTypeResolver->getNativeType($args[0]->value);
         $secondArgType = TypeCombinator::removeNull($this->nodeTypeResolver->getNativeType($args[1]->value));
 
+        // union type can hold different types that assertEquals() compares loosely, keep it safe
+        if ($secondArgType instanceof UnionType) {
+            return true;
+        }
+
         // loose comparison
         if ($firstArgType instanceof IntegerType && ($secondArgType instanceof FloatType || $secondArgType instanceof StringType)) {
             return true;