I'm trying to accept delegates or functions in a templated method.

My first try using "isDelegate!dg || isFunctionPointer!dg" did not work because isDelegate fails, although I'm not sure I understand exactly why:

    void main()
    {
        int x;
        static assert(isDelegate!(() { x = 4; }));
        // Error: static assert ... is false
    }

If I changed that example to use isSomeFunction it works correctly. But when I tried to use isSomeFunction in the proper context it fails to compile:

    class A
    {
        void foo(alias dg)()
            if(isSomeFunction!dg)
        {
        }
    }

    void main()
    {
        int x;
        A a = new A;
        a.foo!((int param) { x = 4;});

        // error: cannot use local '__lambda1' as parameter to non-global
                      template foo(alias dg)() if (isSomeFunction!(dg))
    }

Can anyone help me understand this?

On 05/27/2013 07:05 AM, "Luís Marques" <luismarques@gmail.com>" wrote:

> If I changed that example to use isSomeFunction it works correctly. But
> when I tried to use isSomeFunction in the proper context it fails to
> compile:

It is a red herring. The code fails to compile even without isSomeFunction.

import std.traits;

>      class A
>      {
>          void foo(alias dg)()
>              if(isSomeFunction!dg)
>          {
>          }
>      }
>
>      void main()
>      {
>          int x;
>          A a = new A;
>          a.foo!((int param) { x = 4;});
>
>          // error: cannot use local '__lambda1' as parameter to non-global
>                        template foo(alias dg)() if (isSomeFunction!(dg))
>      }
>
> Can anyone help me understand this?

It is an unsolved technical issue about delegates' currently not having sufficient number of context pointers:

  http://d.puremagic.com/issues/show_bug.cgi?id=5710

Ali