The following program produces the wrong error message:

interface A {
}

class Test {
    A foo() {
        return this;
    }
}

The error is:

T.java:6: Incompatible type for return. Can't convert Test to A.
        return this;
        ^


It should be:

T.java:6: Incompatible type for return. Explicit cast needed to convert Test to A.
        return this;
        ^