The error occurs only if $ (or length) is used to slice the array:

----
template Foo(A...)
{
    const Foo = cast(int[])[A]; // BTW, why is the cast required here?
}

void main()
{    
    foreach (i; Foo!(1, 2)[1 .. $])
    {
    }
}
----
Error 42: Symbol Undefined _D4test4mainFZv8__dollark

The error disappears if the array length is accessed explicitly or the test is built with -release switch.