Trying to use Mir ion, its a perfect example of the failure of D's attribute system

[Walter Bright]

Consider:

  void delegate() dg;

  // no error
  void process(void delegate() userData) @nogc { dg = userData; }

  // Error: `@nogc` function `process2` cannot call non- at nogc delegate `userData`
  void process2(void delegate() userData) @nogc { userData(); }

If process() is made into a template, it will "inherit" @nogc based on whether 
the delegate is called or not.