Fix Castables issue #1312 (#1388)

* Return Castable class if failed to detect it from return types

* fix-style

* Add CHANGELOG.md entry

src/Console/ModelsCommand.php

@@ -1347,7 +1347,7 @@ class ModelsCommand extends Command
 
         return $this->getReturnTypeFromReflection($methodReflection) ??
             $this->getReturnTypeFromDocBlock($methodReflection, $reflection) ??
-            'mixed';
+            $type;
     }
 
     /**