Question on exception transparency

[Peter Levart]

On 08/12/10, Maurizio Cimadamore wrote:
> On 12/08/10 13:40, Peter Levart wrote:
> > import java.util.*;
> >
> > public class Closures
> > {
> >    public interface Block<T, throws E>  { void run(T param) throws E; }
> >
> >    public static<T, throws E>
> >      void forEach(Iterable<T>  iterable, Block<? super T, E>  block) throws E
> >    {
> >      for (T obj : iterable) block.run(obj);
> >    }
> >
> >    public static void main(String[] args)
> >    {
> >      // example 1:
> >      forEach(
> >        Arrays.asList("a", "b", "c"),
> >        #(String s){ System.out.println("element: " + s); }
> >      );
> >
> > // example 2 - javac throws NPE:
> > //    Closures.<String, void>forEach(
> > //      Arrays.<String>asList("a", "b", "c"),
> > //      Block<String, void>  #(String s){ System.out.println("element: " + s); }
> > //    );
> >    }
> > }
> >    
> The following works for me:
> 
> Closures.forEach(
>        Arrays.<String>asList("a", "b", "c"),
>        Block<String, void> #(s){ System.out.println("element: " + s); }
>      );
> 
> I guess  the NPE has been fixed in the last push.
> 

Yes, that works now. But the following:

      forEach(
         Arrays.asList("a", "b", "c"),
         #(String s){ System.out.println("element: " + s); }
      );

... is currently no better than:

      forEach(
         Arrays.asList("a", "b", "c"),
         #(s){ System.out.println("element: " + s); }
      );


They both infer "Exception" as the thrown type. Can this be improved? Is specifying lambda expression's parameter type actualy doing any help here?

My naive uninformed understanding is that If the algorithm for method resolution worked in 2 passes:

1st pass would resolve method without taking into account throws type parameters
2nd pass would "check and apply" throws type parameters for the resolved method

...then even in the presence of overloaded methods exception transparency could work without explicitly specifying type parameters either on method or prefixing lambda with target SAM type.

Peter