--- parent.d

import childb;

import defs;

class Parent

{

    enum CONSTANT = defs.CONSTANT;

}

​

--- childa.d

import parent;

import helpers;

class ChildA : Parent

{

    mixin(ctfeFunc(true));

}

​

--- childb.d

import parent;

import helpers;

class ChildB : Parent

{

    mixin(ctfeFunc());

}

​

--- defs.d 

import childa;

enum CONSTANT = "";

​

--- helpers.d

string ctfeFunc(bool)

{

    import std.ascii;

    return "";

}

string ctfeFunc()

{

    return ctfeFunc(false);

}