The following test produces incorrect behavior for the post-increment operator when it is applied to a boxed Integer being returned from a lambda body.

public class LambdaIncrement {

interface IntOp { int apply(int arg); }
interface IntegerOp { Integer apply(Integer arg); }

static Integer field = 0;

public static final void main(String... args) {
  IntOp preInc = x -> ++x;
  IntegerOp preIncBox1 = x -> ++x;
  IntegerOp preIncBox2 = x -> { return ++x; };
  IntegerOp preIncBox3 = x -> { int y = x; return ++y; };
  IntegerOp preIncBox4 = x -> { Integer y = x; return ++y; };
  IntegerOp preIncField = x -> ++field;
  IntOp postInc = x -> x++;
  IntegerOp postIncBox1 = x -> x++;
  IntegerOp postIncBox2 = x -> { return x++; };
  IntegerOp postIncBox3 = x -> { int y = x; return y++; };
  IntegerOp postIncBox4 = x -> { Integer y = x; return y++; };
  IntegerOp postIncField = x -> field++;
  System.out.println("preInc(3): " + preInc.apply(3)); // expected: 4; actual: 4
  System.out.println("preIncBox1(3): " + preIncBox1.apply(3)); // expected: 4; actual: 4
  System.out.println("preIncBox2(3): " + preIncBox2.apply(3)); // expected: 4; actual: 4
  System.out.println("preIncBox3(3): " + preIncBox3.apply(3)); // expected: 4; actual: 4
  System.out.println("preIncBox4(3): " + preIncBox4.apply(3)); // expected: 4; actual: 4
  System.out.println("postInc(3): " + postInc.apply(3)); // expected: 3; actual: 3
  System.out.println("postIncBox1(3): " + postIncBox1.apply(3)); // expected: 3; actual: 4
  System.out.println("postIncBox2(3): " + postIncBox2.apply(3)); // expected: 3; actual: 4
  System.out.println("postIncBox3(3): " + postIncBox3.apply(3)); // expected: 3; actual: 3
  System.out.println("postIncBox4(3): " + postIncBox4.apply(3)); // expected: 3; actual: 4
  System.out.println("preIncField(3): " + preIncField.apply(3)); // expected: 1; actual: 1
  System.out.println("postIncField(3): " + postIncField.apply(3)); // expected: 1; actual: 1
}

}