Fix #3047

Author: bcobzh

src/Bridge/NelmioApiDoc/Parser/ApiPlatformParser.php

@@ -235,7 +235,7 @@ private function parseProperty(ResourceMetadata $resourceMetadata, PropertyMetad
         if ('object' === $builtinType) {
             $className = $type->getClassName();
 
-            if (is_subclass_of($className, \DateTimeInterface::class)) {
+            if (is_a($className, \DateTimeInterface::class, true)) {
                 $data['dataType'] = DataTypes::DATETIME;
                 $data['format'] = sprintf('{DateTime %s}', \DateTime::RFC3339);
 

src/Swagger/Serializer/DocumentationNormalizer.php

@@ -675,7 +675,7 @@ private function getType(bool $v3, string $type, bool $isCollection, ?string $cl
                 return ['type' => 'string'];
             }
 
-            if (is_subclass_of($className, \DateTimeInterface::class)) {
+            if (is_a($className, \DateTimeInterface::class, true)) {
                 return ['type' => 'string', 'format' => 'date-time'];
             }