A template for method forwarding?

[Fawzi Mohamed]

On 2008-12-13 15:29:19 +0100, Christopher Wright <dhasenan at gmail.com> said:

> Christian Kamm wrote:
>>> So looks like bad stringof is the culprit, once again.
>> 
>> Why use stringof when you have an alias? This works for me in D1 - if you
>> discount default arguments and parameter storage classes (will templates
>> ever be able to touch these?).
> 
> stringof sucks, but it's easy to work with.
> 
> Your solution doesn't deal with method overloads. Passing in a method 
> alias would work:
> 
> template Forward(string classname, alias method)
> {
>     mixin ("ReturnTypeOf!(method) " ~ method.stringof ~ 
> "(ParameterTupleOf!(Method) parameters) {
> 	return composed." ~ method.stringof ~ "(parameters);
> 	}");
> }
> 
> Except method.stringof doesn't work, so you have to do it like this:
> template strof(alias method)
> {
>      const strof = (&method).stringof[2..$];
> }
> 
> template Forward(char[] classname, alias method)
> {
>     mixin ("ReturnTypeOf!(method) " ~ strof!(method) ~ 
> "(ParameterTupleOf!(method) parameters) {
>          return composed." ~ strof!(method) ~ "(parameters); }");
> }

In my testing framework I had first a version using stringof, and I was 
able to pass the type or alias directly, this solved many issues.
I think that if doable passing types and aliases is indeed better than strings.

somewhat related to this topic I just found out that is(... 
return/function/delegate) behave in a way that I did not expect, given 
a method that returns an int and one that has an int argument (get/set) 
one has:

typeof(&A.ret_int):int function()
typeof(&A.ret_int) U==return:int
typeof(&A.init.ret_int):int delegate()
typeof(&A.init.ret_int) T==return:int
typeof(&A.init.ret_int) T==delegate:int
typeof(&A.ret_void):void function(int a)
typeof(&A.ret_void) U==return:int
typeof(&A.init.ret_void):void delegate(int a)
typeof(&A.init.ret_void) T==return:int
typeof(&A.init.ret_void) T==delegate:int

for me it is ok as I wanted to have the type of the property 
getter/setter, but it is not what I would have expected from the 
documentation...
The prviosu running this program

{{{
import tango.io.Stdout;

class A{
  int ret_int(){ return 3; }
  void ret_void(int a){ }
}

void main(){
   Stdout("typeof(&A.ret_int):")(typeof(&A.ret_int).stringof).newline;
   static if(is(typeof(&A.ret_int) U==function))
        Stdout("typeof(&A.ret_int) U==function:")(U.stringof).newline;
   static if(is(typeof(&A.ret_int) U==return))
        Stdout("typeof(&A.ret_int) U==return:")(U.stringof).newline;
   
Stdout("typeof(&A.init.ret_int):")(typeof(&A.init.ret_int).stringof).newline;
 

  static if(is(typeof(&A.init.ret_int) T==return)){
        Stdout("typeof(&A.init.ret_int) T==return:")(T.stringof).newline;
   }
   static if(is(typeof(&A.init.ret_int) T==function)){
        Stdout("typeof(&A.init.ret_int) T==function:")(T.stringof).newline;
   }
   static if(is(typeof(&A.init.ret_int) T==delegate)){
       Stdout("typeof(&A.init.ret_int) T==delegate:")(T.stringof).newline;
       static if(is(T U==function))
            Stdout("&A.init.ret_int delegate function:")(U.stringof).newline;
       static if(is(T U==return))
            Stdout("&A.init.ret_int delegate return:")(U.stringof).newline;
   }
   Stdout("typeof(&A.ret_void):")(typeof(&A.ret_void).stringof).newline;
   static if(is(typeof(&A.ret_void) U==function))
        Stdout("typeof(&A.ret_void) U==function:")(U.stringof).newline;
   static if(is(typeof(&A.ret_void) U==return))
        Stdout("typeof(&A.ret_void) U==return:")(U.stringof).newline;
   
Stdout("typeof(&A.init.ret_void):")(typeof(&A.init.ret_void).stringof).newline;
 

  static if(is(typeof(&A.init.ret_void) T==return)){
        Stdout("typeof(&A.init.ret_void) T==return:")(T.stringof).newline;
   }
   static if(is(typeof(&A.init.ret_void) T==delegate)){
       Stdout("typeof(&A.init.ret_void) T==delegate:")(T.stringof).newline;
       static if(is(T U==function))
            Stdout("typeof(&A.init.ret_void) delegate 
function:")(U.stringof).newline;
       static if(is(T U==return))
            Stdout("typeof(&A.init.ret_void) delegate 
return:")(U.stringof).newline;
   }
}
}}}