Circular reference error gone after inspecting members

[Yuxuan Shui via Digitalmars-d-learn]

The offending code base is a little big and hard to reduce. I'll 
try if code is required, but here is the gist of the problem:

This snippet of code in my project:
    ...
    alias tmp = genCode!T;
    enum str = tmp.str; // This line here
    ...

Generate a circular reference error.

However, if I do:

    ...
    alias tmp = genCode!T;
    pragma(msg, __traits(allMembers, tmp));
    enum str = tmp.str; // This line here
    ...

Then the error is gone.

Anyone has any idea what could the problem be?