Allow falsable issues on DateInterval::$days

Author: muglug

src/Psalm/Internal/Codebase/Reflection.php

@@ -130,18 +130,22 @@ public function registerClass(\ReflectionClass $reflected_class)
 
         // have to do this separately as there can be new properties here
         foreach ($public_mapped_properties as $property_name => $type) {
+            $property_id = $class_name . '::$' . $property_name;
+
             if (!isset($storage->properties[$property_name])) {
                 $storage->properties[$property_name] = new PropertyStorage();
                 $storage->properties[$property_name]->visibility = ClassLikeAnalyzer::VISIBILITY_PUBLIC;
 
-                $property_id = $class_name . '::$' . $property_name;
-
                 $storage->declaring_property_ids[$property_name] = $class_name;
                 $storage->appearing_property_ids[$property_name] = $property_id;
                 $storage->inheritable_property_ids[$property_name] = $property_id;
             }
 
             $storage->properties[$property_name]->type = Type::parseString($type);
+
+            if ($property_id === 'DateInterval::$days') {
+                $storage->properties[$property_name]->type->ignore_falsable_issues = true;
+            }
         }
 
         /** @var array<string, int|string|float|null|array> */