http://forum.dlang.org/thread/odqtleucashpjekvtjsv@forum.dlang.org
DMD 2.063
Ali Çehreli's test case:

import std.typecons;

struct S
{
    int x;

    // Bizarre: Comment-out this function to pass the assert in main.
    Tuple!(S) unused()
    {
        return tuple(S(7));
    }
}

void main()
{
    auto s = S(8);
    assert(tuple(s).expand[0] == S(8));
}