Is it possible for Scala to have reified generics without changing the JVM?

Question

I\'ve recently started learning Scala and was disappointed (but not surprised) that their generics are also implemented via type erasure.

My question is, is it possi

Answer 1

To complement oxbow_lakes answer: It is no possible and it seems it will never happen (at least soon).

The (refutable) reasons JVM will not support reified generics seems to be:

• Lower performance.
• It breaks backward compatibility. It can be solved duplicating and fixing a lot of libraries.
• It can be implemented using manifests: The "solution" and the biggest impediment.

References:

• Odersky comment in 2010: "I prefer a simpler VM architecture with type erasure"

• In scala-internals list (Feb 2013) Grzegorz Kossakowski said:

You can easily benchmark it and see that performance impact is very noticeable. Especially memory consumption increases a lot.

I believe the way to go is to have optional reification the way we start to do in Scala with Manifests/TypeTags.

If you can and combine it with runtime specialization you can aim for high performance and generic code. However, that's probably goal for Scala 2.12 or 2.13.