Serialization opt-in syntax (again)

[Kevin Bourrillion]

I don't think it changes much. These words still don't feel like they
belong there. The fact of serializability has really intruded into the
center of the expression...



On Fri, Sep 28, 2012 at 1:14 PM, Bob Lee <crazybob at crazybob.org> wrote:

> 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.
>>
>>
>


-- 
Kevin Bourrillion | Java Librarian | Google, Inc. | kevinb at google.com
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