> This is equally true in Java. Types are erased at runtime. They don't exist in the bytecode.

I work with bytecode on a daily basis (I develop a commercial Java obfuscator) and this is untrue. You may be thinking of generic type parameter erasure, but even then special interface methods are generated by the compiler so that no lowering to java/lang/Object happens too soon.

In non-generic code, the types remain and are strongly enforced. Methods have descriptors that restrict parameters to certain types (you can get a VerifyError upon loading the class if you've generated code with a type confusion), there is a 'checkcast' instruction to ensure that a stack values is a certain type, and a ClassCastException is thrown if a cast is impossible.