Re:Modern programming languages require generics
by titzer on Tuesday May 24, 2022 @10:15PM
(#31499897)
> if there was no reflection (which is not that common feature in languages) one could not even differentiate between the two models. Haskell also does complete type erasure for example.
You can, even without reflection, because the Java generic type system doesn't have the parametricity property; you can detect runtime types with cast/instanceof. Haskell doesn't have non-parametric operations, so erasure is not observable.
Also, I don’t see erased generics all that big of a deal — if there was no reflection (which is not that common feature in languages) one could not even differentiate between the two models. Haskell also does complete type erasure for example.
As for another view point, it is often brought up on HN that what made the JVM language ecosystem so thriving is exactly the type erasure model. C# effectively forces their idea of generics onto the whole platform, while JVM languages are free to choose their own model. I don’t know how true is that, but empirically it does seem to sound true (F# does share its generics model with C#, and the CLR has a history of getting some attempts at being a target which is later dropped. Though I assume it is more often due to it simply being a smaller target)