Identify return type of an expression written in monaco editor using API

[NrujalSharma]

I am using monaco editor and have a class declared as follows and added using the addExtraLib to the editor

class User {
  id: number;
  age: number;
  firstName: string; 
  lastName: string; 
}

In the editor the user can write something like:

user1.age > user2.age

and I need to be able to identfy that the return type of this is boolean

And the user can also write something something like:

user1.firstName + ' ' + user1.lastName

and I need to be able to identfy that the return type of this is string

User can write any other type of expression using the user class and I want to identify the return type of that code snippet

How to do that?