[Issue 3180] Need delegate covariance and contravariance

[d-bugmail at puremagic.com]

http://d.puremagic.com/issues/show_bug.cgi?id=3180





--- Comment #2 from Haruki Shigemori <rayerd.wiz at gmail.com>  2009-07-17 16:55:58 PDT ---
(In reply to comment #1)
> Your contravariance example is not valid, you cannot call foo(B) with an A.
> 
> It should be:
> 
> class V
> {
>   void foo(A);
> }
> 
> 
> ...
> 
> V v = new v;
> void delegate(B) g = &v.foo; // contravariance

Sorry, it is my mistake.

> Also this is somewhat of a duplicate of bug 3075.  Although you do bring up
> covariance for delegates, which should be implemented at the same time as
> contravariance.
> 
> Sadly, Walter has decided the prior bug is an invalid enhancement request, so
> most likely nothing will come of this request either.

OMG. It is so sad. There are both in C#.

> I think the only possible way this may be included is if someone implements it
> and submits it as a patch to dmd.

I am trying to make some dmd patchs, but it is difficult yet.

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