How to specify a template that uses unqualified type, like any normal function

[Dominikus Dittes Scherkl via Digitalmars-d-learn]

if I use fixed-type functions, I can do the following:

uint foo(uint n)
{
    ++n; // modify n - as this function has received a copy of n, 
this is always possible
    return 42;
}

uint bar(const uint n)
{
    assert(foo(n)==42);
    return 17;
}

void main()
{
    bar(3);
}


But if I try the same with a template parameter, it doesn't work:

import std.traits; // Unqual

uint foo(T)(Unqual!T n) // first try
{
    ++n; // modify should be possible
    return 42;
}

uint foo2(T)(T n) // second try
{
    ++n; // modify fails, as T is const
    return 42;
}

uint bar(T)(const T n)
{
    assert(foo(n)==42u); // cannot deduce arguments - why?!?
    assert(foo2(n)==42u); // here it can deduce the arguments, but 
the function cannot modify n
    return 17;
}

void main()
{
    bar(3);
}

Any ideas what I need to do to make this work?