Реализовал поддерку интерфейсов.

Нужен рефакторинг.
Метод разрастается

src/Data2DtoConverter.php

@@ -42,10 +42,27 @@ class Data2DtoConverter
                     continue;
                 }
 
+                $preparedPropertyType = $propertyType;
+
+                if (interface_exists($preparedPropertyType)) {
+                    $attributedPropertyClass = $this->grabPropertyDTOClass($property);
+                    // Если не указали мета информацию для интерфейса - пропустим
+                    if (!$attributedPropertyClass) {
+                        continue;
+                    }
+                    // Если класс не реализует интерфейс свойства - пропустим
+                    $interfaces = class_implements($attributedPropertyClass);
+                    if (!isset($interfaces[$preparedPropertyType])) {
+                        continue;
+                    }
+                    $preparedPropertyType = $attributedPropertyClass;
+                }
+
                 // Если это class, то рекурсивно заполняем дальше
-                if (class_exists($propertyType)) {
-                    $value = $this->convert($value, $propertyType);
+                if (class_exists($preparedPropertyType)) {
+                    $value = $this->convert($value, $preparedPropertyType);
                 }
+
                 // присваиваем получившееся значение
                 $property->setValue($object, $value);
             }
@@ -109,13 +126,7 @@ class Data2DtoConverter
 
     private function transformArray(&$value, \ReflectionProperty $property): bool
     {
-        $attributedPropertyClass = null;
-        $propertyName = $property->getName();
-        $propertyExtractor = new PropertyExtractor($property->class, $propertyName);
-        /** @var DTOMeta $dtoMeta */
-        if ($dtoMeta = $propertyExtractor->fetch(DTOMeta::class)) {
-            $attributedPropertyClass = $dtoMeta->class;
-        }
+        $attributedPropertyClass = $this->grabPropertyDTOClass($property);
 
         /** @var \ReflectionNamedType $reflectionPropertyType */
         $reflectionPropertyType = $property->getType();
@@ -135,4 +146,16 @@ class Data2DtoConverter
         }
         return true;
     }
+
+    private function grabPropertyDTOClass(\ReflectionProperty $property): ?string
+    {
+        $attributedPropertyClass = null;
+        $propertyName = $property->getName();
+        $propertyExtractor = new PropertyExtractor($property->class, $propertyName);
+        /** @var DTOMeta $dtoMeta */
+        if ($dtoMeta = $propertyExtractor->fetch(DTOMeta::class)) {
+            $attributedPropertyClass = $dtoMeta->class;
+        }
+        return $attributedPropertyClass;
+    }
 }

tests/unit/Converter/FillTest.php

@@ -3,6 +3,7 @@
 namespace Rinsvent\Data2DTO\Tests\Converter;
 
 use Rinsvent\Data2DTO\Data2DtoConverter;
+use Rinsvent\Data2DTO\Tests\unit\Converter\fixtures\FillTest\Bar;
 use Rinsvent\Data2DTO\Tests\unit\Converter\fixtures\FillTest\BuyRequest;
 use Rinsvent\Data2DTO\Tests\unit\Converter\fixtures\FillTest\HelloRequest;
 
@@ -47,6 +48,9 @@ class FillTest extends \Codeception\Test\Unit
                 'isFirst' => true,
                 'extraData2' => '1234'
             ],
+            'bar' => [
+                'barField' => 32
+            ],
             'extraData1' => 'qwer'
         ], HelloRequest::class);
         $this->assertInstanceOf(HelloRequest::class, $dto);
@@ -65,5 +69,9 @@ class FillTest extends \Codeception\Test\Unit
         $this->assertCount(2, $dto->authors);
         $this->assertEquals('Tolkien', $dto->authors[0]->name);
         $this->assertEquals('Sapkovsky', $dto->authors[1]->name);
+
+        $this->assertInstanceOf(Bar::class, $dto->bar);
+        $this->assertIsFloat($dto->bar->barField);
+        $this->assertEquals(32.0, $dto->bar->barField);
     }
 }

tests/unit/Converter/fixtures/FillTest/Bar.php

@@ -0,0 +1,8 @@
+<?php
+
+namespace Rinsvent\Data2DTO\Tests\unit\Converter\fixtures\FillTest;
+
+class Bar implements BarInterface
+{
+    public float $barField;
+}

tests/unit/Converter/fixtures/FillTest/BarInterface.php

@@ -0,0 +1,8 @@
+<?php
+
+namespace Rinsvent\Data2DTO\Tests\unit\Converter\fixtures\FillTest;
+
+interface BarInterface
+{
+
+}

tests/unit/Converter/fixtures/FillTest/HelloRequest.php

@@ -16,4 +16,6 @@ class HelloRequest
     #[DTOMeta(class: Author::class)]
     public array $authors;
     public BuyRequest $buy;
+    #[DTOMeta(class: Bar::class)]
+    public BarInterface $bar;
 }