[TypeDeclarationDocblocks] Handle array union type on DocblockVarArrayFromPropertyDefaultsRector

rules-tests/TypeDeclarationDocblocks/Rector/Class_/DocblockVarArrayFromPropertyDefaultsRector/Fixture/array_union_generic_same_type.php.inc

@@ -0,0 +1,36 @@
+<?php
+
+namespace Rector\Tests\TypeDeclarationDocblocks\Rector\Class_\DocblockVarArrayFromPropertyDefaultsRector\Fixture;
+
+use DateTime;
+use stdClass;
+
+class ArrayUnionGenericSameType
+{
+    protected array $dependencies = [
+        stdClass::class,
+        DateTime::class,
+    ];
+}
+
+?>
+-----
+<?php
+
+namespace Rector\Tests\TypeDeclarationDocblocks\Rector\Class_\DocblockVarArrayFromPropertyDefaultsRector\Fixture;
+
+use DateTime;
+use stdClass;
+
+class ArrayUnionGenericSameType
+{
+    /**
+     * @var array<int, class-string<\stdClass>|class-string<\DateTime>>
+     */
+    protected array $dependencies = [
+        stdClass::class,
+        DateTime::class,
+    ];
+}
+
+?>

src/BetterPhpDocParser/ValueObject/Type/SpacingAwareArrayTypeNode.php

@@ -6,6 +6,7 @@
 
 use PHPStan\PhpDocParser\Ast\Type\ArrayTypeNode;
 use PHPStan\PhpDocParser\Ast\Type\CallableTypeNode;
+use PHPStan\PhpDocParser\Ast\Type\GenericTypeNode;
 use PHPStan\PhpDocParser\Ast\Type\TypeNode;
 use PHPStan\PhpDocParser\Ast\Type\UnionTypeNode;
 use Rector\PHPStanStaticTypeMapper\TypeMapper\ArrayTypeMapper;
@@ -60,12 +61,44 @@ private function printArrayType(ArrayTypeNode $arrayTypeNode): string
 
     private function printUnionType(BracketsAwareUnionTypeNode $bracketsAwareUnionTypeNode): string
     {
-        $unionedTypes = [];
-
         if ($bracketsAwareUnionTypeNode->isWrappedInBrackets()) {
             return $bracketsAwareUnionTypeNode . '[]';
         }
 
+        // If all types in the union are GenericTypeNode, use array<union> syntax
+        $allGeneric = true;
+        $firstGenericTypeName = null;
+
+        foreach ($bracketsAwareUnionTypeNode->types as $unionedType) {
+            if (! $unionedType instanceof GenericTypeNode) {
+                $allGeneric = false;
+                break;
+            }
+
+            // ensure only check on base level
+            // avoid mix usage without [] added
+            if (count($unionedType->genericTypes) !== 1) {
+                $allGeneric = false;
+                break;
+            }
+
+            // ensure all generic types has the same base type
+            $currentTypeName = $unionedType->type->name;
+
+            if ($firstGenericTypeName === null) {
+                $firstGenericTypeName = $currentTypeName;
+            } elseif ($firstGenericTypeName !== $currentTypeName) {
+                // Different generic base types (e.g., class-string vs array)
+                $allGeneric = false;
+                break;
+            }
+        }
+
+        if ($allGeneric) {
+            return sprintf('array<int, %s>', (string) $bracketsAwareUnionTypeNode);
+        }
+
+        $unionedTypes = [];
         foreach ($bracketsAwareUnionTypeNode->types as $unionedType) {
             $unionedTypes[] = $unionedType . '[]';
         }