Re: Making TypeInfo.next() return a const(TypeInfo) was a bad idea

[Rainer Schuetze]

On 10/14/2012 12:19 PM, Benjamin Thaut wrote:
Because you are now no longer able to do stuff like this:

void log(...)
{
   auto t = _arguments[0];
   while(some condition)
   {
     t = t.next();
   }
}

To be actually able to use TypeInfo.next you will now need the ConstRef
(hack) from phobos. Afaik there is no such thing in druntime which makes
working with TypeInfo.next within druntime a real pita.

That's the general problem of non-rebindable const references which is a 
real pita. There has been a pull request to implement it 
(https://github.com/D-Programming-Language/dmd/pull/3) but unfortunately 
it never made it into the compiler.


Any suggestions?

You could create a recursive function hoping for 
tail-recursion-optimization and inlining:

void log(...)
{
   static const(TypeInfo) drillInto(const(TypeInfo) t)
   {
      if(some condition)
        return drillInto(t.next());
      return t;
   }
   auto t = drillInto(_arguments[0]);
}