can already defined types be modified at compile time with a macro?

[JohnAD]

I can write a macro that allows me to do this:
    
    
    my_macro_adds_age:
      type
        SomeType = object
          name: string
    
    let a = SomeType(name: "Bob", age: 30)
    
    
    Run

No problem.

But, I'm curious, is it even possible (and safe) to modify a type after the 
definition? Something akin to:
    
    
    type
      SomeType = object
        name: string
    
    my_other_macro_adds_age(SomeType)
    
    let a = SomeType(name: "Bob", age: 30)
    
    
    Run