Serialization opt-in syntax (again)

[Bob Lee]

I like the semantics a lot! Maybe moving the "implements" decl to the right
of the -> would address Kevin's concerns? Then it would read "lambda (->)
implements ..."

Bob

On Fri, Sep 28, 2012 at 1:47 PM, Brian Goetz <brian.goetz at oracle.com> wrote:

> I put all the candidate syntaxes so far in the JIRA issue for this, but a
> new one came to light this week that we kind of like.
>
> The problem is: let's say you have a SAM that is not serializable, but you
> want the instance to be, such as in:
>
>   Runnable r = () -> { };
>
> The problem is that we really want to specify multiple interfaces for the
> lambda, and as long as their intersection has only one abstract method,
> that should be OK.
>
> So, how about using the space between the closing paren and the arrow:
>
>   Runnable r = () implements Serializable -> { ... }
>
> As a bonus, if we wanted to be explicit about all the implemented
> interfaces, this easily extends to:
>
>   Object p = (String s) implements Predicate<String>, Serializable -> {
> ... }
>
>
> This also extends nicely to inner class creation expressions.  Right now
> there is a limit of one named supertype.  But this could be extended:
>
>   Predicate<String> p = new Predicate<String>() implements Serializable {
> ... }
>
> In this case, there is no single-method restriction; you could implement
> Iterator and Runnable if you wanted:
>
>   new Iterator<T>() implements Runnable { ... }
>
> Note that none of this is serialization-specific; it is simply a way of
> being explicit about multiple supertypes in contexts there this was not
> previously allowed.
>
>