Macro accessing fields of struct at another module

General Usage
2

You can write this:

julia> module MyModule
         export @mymacro
         macro mymacro(T)
           @show T typeof(T)  # at macro expansion
           :(fieldnames($(esc(T))))  # returned Expr
         end
       end;

julia> mutable struct Person
          id::Int
          name::String
       end;

julia> using .MyModule

julia> @mymacro Person
T = :Person
typeof(T) = Symbol
(:id, :name)

Although the macro isn’t doing anything, really, it may as well just be a function. One problem with eval (scope/escaping aside) is that the struct this asks about may not even be defined when the macro runs:

julia> f(x::T) where T = @mymacro T;
T = :T
typeof(T) = Symbol

julia> f(Person(1, "me"))
(:id, :name)

julia> struct Dog; id::Int; end

julia> f(Dog(2))
(:id,)
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