allow enum casting not only enum value casting

src/Casters/EnumCaster.php

@@ -15,6 +15,10 @@ public function __construct(
 
     public function cast(mixed $value): mixed
     {
+        if ($value instanceof $this->enumType) {
+            return $value;
+        }
+
         if (! is_subclass_of($this->enumType, 'BackedEnum')) {
             throw new LogicException("Caster [EnumCaster] may only be used to cast backed enums. Received [$this->enumType].");
         }

tests/Casters/EnumCasterTest.php

@@ -41,6 +41,18 @@ public function test_it_can_cast_enums(): void
         $this->assertEquals(IntegerEnum::Test, $dto->integerEnum);
     }
 
+    /** @test */
+    public function test_it_can_cast_enums_which_are_already_enums(): void
+    {
+        $dto = new EnumCastedDataTransferObject([
+            'integerEnum' => IntegerEnum::Test,
+            'stringEnum' => StringEnum::Test,
+        ]);
+
+        $this->assertEquals(StringEnum::Test, $dto->stringEnum);
+        $this->assertEquals(IntegerEnum::Test, $dto->integerEnum);
+    }
+
     /** @test */
     public function test_it_cannot_cast_simple_enums(): void
     {