Sometime .offsetof does not compile.
Adding a cast can make it compile

template Test( uint memberOffset ){}

class MyClass {
    int flags2;
    mixin Test!(cast(uint)flags2.offsetof) t1; // compiles ok
    mixin Test!(cast(int)flags2.offsetof)  t2; // compiles ok
    mixin Test!(flags2.offsetof)           t3; // Error: no property 'offsetof' for type 'int'
}