Lambda and intersection types

[Brian Goetz]

So, I was focusing too narrowly on the question the first time I answered.

IF the code compiles, THEN i2 will, at runtime, be an instance of both 
I1 and I2.

But, this code may not compile.  The likely restriction when applied to 
a lambda/method ref conversion, at least initially, is that:
  - I1 be a SAM
  - I2..In be a "ZAM" (zero abstract method)
  - The intersection I1&I2&.. also be a SAM

While the example you post meets the last criteria, it does not meet the 
first two.


On 11/12/2012 3:01 PM, Boaz Nahum wrote:
> Yes, but should it be valid code ?
>
> If yes, I2 implements both I1 & I2 or just I2 ?
>
> Thanks
> Boaz
>
>
>
> On Mon, Nov 12, 2012 at 9:55 PM, Brian Goetz <brian.goetz at oracle.com
> <mailto:brian.goetz at oracle.com>> wrote:
>
>     The back-end work for intersection-typed lambdas is not implemented
>     yet...only the compiler front-end work.
>
>
>     On 11/12/2012 2:45 PM, Boaz Nahum wrote:
>
>         The follwing simple code ...
>
>         ==============================__======
>         interface I1 {void f();}
>
>         interface I2 {
>
>               void printMe()default { System.out.println("I2");}
>
>               void f();
>         }
>
>         public static void main(String[] args) {
>
>                   I2 i2 = (I1 & I2) () -> {};
>
>                   System.out.println( "i2 is I2=" + (i2 instanceof I2));
>
>                   i2.printMe();
>               }
>         ==============================__===
>         Output is:
>
>         ------------------------------__-------
>         i2 is I2=false
>         Exception in thread "main"
>         java.lang.__IncompatibleClassChangeError: Class
>         question.lambda_intersection___types.Q$$Lambda$2 does not
>         implement the
>         requested interface question.lambda_intersection___types.I2
>         ------------------------------__-------
>
>         What is the correct behavior ?
>
>