override(T)

[bearophile]

> Something that may be useful, partially related:
> http://en.wikipedia.org/wiki/Multiple_dispatch
> http://en.wikipedia.org/wiki/Generic_function

Something similar to the CLisp syntax looks good enough for D (I think there's no need to add an explicit mark that reminds there's some runtime cost to be paid in this calls):
void collideWith(Asteroid x, Asteroid y) { ...}
void collideWith(Asteroid x, Spaceship y) { ...}
...

Bye,
bearophile