[typing] Type-erasure re generics

[Jonathan M Davis]

On Wednesday, September 29, 2010 10:18:17 Pelle wrote:
> On 09/29/2010 05:53 PM, Jesse Phillips wrote:
> > The only benefit, which should be solve in another manner is having this
> > code work:
> > 
> > class A {}
> > class B:A {}
> > 
> > class Container(T) {}
> > 
> > void main() {
> > 
> >      Container!(A) a = new Container!(B)();
> > 
> > }
> 
> Sorry for falling off topic, but that code shouldn't work.
> 
> a.insert(new A)

Yeah. Having a container of one type should not be castable to a container of 
another type. They are completely separate types even if they hold types which 
have an is-a relationship. And your example shows one of the reasons why. It's a 
fundamental aspect of the concept of generic containers, not a result of the 
implementation. It _seems_ like it should work, but once you really get into it, 
it quickly becomes apparent that it doesn't.

- Jonathan M Davis