• Wolftein (10/10) Oct 31 2013 void delegate(Event)
• Wolftein (3/13) Oct 31 2013 Well with the last verion delegate and function cast works fine,
• qznc (10/20) Oct 31 2013 It is not safe to allow this.

"Wolftein" <agustin.l.alvarez hotmail.com> writes:

void delegate(Event)
void delegate(T) Where T is a class that inherits Event.

I'm trying to cast (void delegate(T)) to (void delegate(Event)) 
to be able to store them in a map, but when i cast them i get 
null exeception.

Same thing for cast things like this

TemplateClass!Plugin
TemplateClass!OtherTypeOfPlugin -> Being OtherTypeOfPlugin 
inherit Plugin

Using C++ this is allowed.

"Wolftein" <agustin.l.alvarez hotmail.com> writes:

On Thursday, 31 October 2013 at 13:12:31 UTC, Wolftein wrote:
 void delegate(Event)
 void delegate(T) Where T is a class that inherits Event.

 I'm trying to cast (void delegate(T)) to (void delegate(Event)) 
 to be able to store them in a map, but when i cast them i get 
 null exeception.

 Same thing for cast things like this

 TemplateClass!Plugin
 TemplateClass!OtherTypeOfPlugin -> Being OtherTypeOfPlugin 
 inherit Plugin

 Using C++ this is allowed.

Well with the last verion delegate and function cast works fine, 
but not for TemplateClass.

"qznc" <qznc web.de> writes:

On Thursday, 31 October 2013 at 13:12:31 UTC, Wolftein wrote:
 void delegate(Event)
 void delegate(T) Where T is a class that inherits Event.

 I'm trying to cast (void delegate(T)) to (void delegate(Event)) 
 to be able to store them in a map, but when i cast them i get 
 null exeception.

 Same thing for cast things like this

 TemplateClass!Plugin
 TemplateClass!OtherTypeOfPlugin -> Being OtherTypeOfPlugin 
 inherit Plugin

 Using C++ this is allowed.

It is not safe to allow this.

   auto f = delegate(T x) { x.methodOfT(); }
   auto g = cast(void delegate(Event)) f;
   g(new Event());

This would call methodOfT on an Event object, which does not have 
that method.

Co- and Contravariance for such stuff is tricky. Here is a 


http://stackoverflow.com/questions/245607/how-is-generic-covariance-contra-variance-implemented-in-c-sharp-4-0