[chubot]

It's definitely the case for generics, as someone pointed out.

If you look at the JVM byte code, you can see this has to be the case: http://en.wikipedia.org/wiki/Java_bytecode

Once you're in byte code, you don't have your static types anymore -- that is, types that are independent of control flow. You have types on individual instructions.

So basically you lost some type information before the JIT even sees it. Now, it doesn't actually matter for speed, as Mike Pall (LuaJIT author) would say. His point is that dynamically typed languages can be just as fast as statically typed languages, because you have more information at runtime.