java - Lambda and cast intersection type (Eclipse compiler bug) -

so, why code compile?

public static void main(string[] args) {     calculator test = (calculator & sumator) (a, b) -> + b;     system.out.println(test.calculate(2, 3));      sumator sumator = (calculator & sumator) (a, b) -> + b; // compile, throws exception     sumator.test();      both both = (both) (a, b) -> + b; // not compile }  interface calculator {     public int calculate(int a, int b); }  interface sumator {     public int test();      public int test3(int a, int b); }  // intersection of both types interface both extends sumator, calculator {  } 

this sort of misleading, know casting intersection type, i've read jls, still confusing.

it sort of makes sense why

 serializable & comparable  

would compile, since result (the synthetic type) between 2 functional interface, why :

 calculator & sumator  

works? synthetic type not functional interface.

this bug in eclipse has been fixed milestone 6 towards eclipse neon (4.6).