Templated delegate

[Mitja]

I would like to have a template which returns
appropriate delegate, something like this:

module mod1;

import std.algorithm;
import std.array;
import std.stdio;

template DG(RT, T, F)
{
  auto DG(F fun)
  {
    RT delegate(T p)dg;
    dg = fun;
    return dg;
  }
}


void main()
{
  string[] haystack = ["item 1", "item 2", "item 3"];
  string needle = "item 2";

  auto flt = (string s){return s == needle;};

  auto dg = DG!(bool, string, typeof(flt))(flt);

  auto result = filter!(dg)(haystack);

  writeln(result);
}

The thing is I don't know what am I doing wrong here,
because sometimes works and sometimes doesn't.
For instance, if I'd added another file along with mod1.d, let's say,
mod2.d which contained:

module mod2;

import std.conv;
import std.string;
import std.random;

and compiled it like this: dmd mod2.d mod1.d, the program would produce
segmentation fault.
It works fine when packages in mod2 are omitted.

What would be the correct way for templated delegate?