Java's type erasure, while once considered a disadvantage, is now being recognized as one of the reasons other statically typed languages can be ported to the JVM. If Java reified types, it would make interoperability with other type systems extremely hard.
Yep, scala's .net back-end is discontinued, and one of the main challenges (I worked on it a bit) was indeed generating the proper generic signatures. (I hear people are using ikvm these days.)
For more context on why F# does in fact run into problems, see https://visualstudio.uservoice.com/forums/121579-visual-stud.... To my understanding, F# only allows type variables to vary, not type constructors (all generic variables must be escorted by a concrete type), and to go a step further, it doesn't allow type constructors to be used as higher-kinded type variables, which is useful sometimes. I see no reason why these couldn't be implemented on top of the JVM, though.
I've never understood why Java programmers dislike type erasure. In my mind, runtime type inspection is a bad idea for a supposedly statically typed language. It just seems like people are complaining that they can't do something they probably shouldn't be. If there's something you can't do without it then that means Java is poorly designed, not that type erasure is a bad idea.
To be fair, erased generics force autoboxing of primitives. Anyway, Java's combination of static and runtime types, though not pure by any measure, has actually proven quite useful.
I see this claim fairly often, but it seems like wishful thinking to me. There's nothing stopping a language targeting .NET from erasing its own generics to `List<object>`, `Map<object>`, `T<object>` if necessary, which would achieve almost exactly what you'd get with Java's erasure. And in the meantime, Java's approach requires any generic class containing arrays to box small value types, wasting large amounts of memory when those arrays are large.
