Custom Principal implementations not recognised by the inspector

This is related to a similar topic: https://intellij-support.jetbrains.com/hc/en-us/community/posts/115000075970-Custom-Spring-Security-Expression-not-recognised-by-the-inspector

In our projects we have implemented the Spring interface UserDetails and a custom UserService for Spring Security for authentication purposes. We have also configured AuthenticationPrincipalArgumentResolver so that we are using the @AuthenticationPrincipal annotation in our controllers.

My problem is that custom methods implemented by us in the User class (implementation of UserDetails) aren't recognised by the inspector in the Spring security expressions.