Generics ignored

Generics in Groovy are mostly a feature for compatibility with Java. You can use them yes, but only what is left after type erasure is really checked. In your case that is nothing.

That's a pity. Is there any chance that generics will be properly supported (ie. as in Java) in the future?

Jochen, I wonder if there is an argument for printing a warning whenever Groovy sees generics, pointing people to a page on the wiki explaining why generics are a fundamental waste of time in any dynamic language that works directly on the JVM?

peninha, The JVM does not store type parameter information for objects instantiated from generic types – the wonders of "type erasure" mean that type parameters are compile time only and dynamic languages such as Groovy do not have access to that information when type checking is undertaken at run time. If you have to have run time type parameter checking then this will require a lot of extra infrastructure on top of the JVM or you have to switch to using CLR. So the upshot is that Groovy will likely never support type parameters unless or until they get included in the JVM.

well imagine

Map<String, Integer> map = x.y()

Java can check this, as it will know the type of x and the return type of the y method. If that information is not available the program won't compile. In Groovy we may not have that information for several reasons. That means we eiter cannot do the check and just accept it (like now) or we fail. Failing at runtime is a problem because the would need to check the generics types on method invocation, wrap the result of the method or other stupid things, which are very bad for performance. Failing at compile time forces a static nature Groovy just does not have.

So we could check some, like your example. But I am not for half hearted things.

Russel, that's the old question of if warnings are making sense or not. I am not so much for warnings. Also were to go with compile time warnings when running a script at runtime from source?

A wiki page might still be a good idea though