FlowBreak.java

import org.checkerframework.checker.fenum.qual.SwingHorizontalOrientation;
import org.checkerframework.checker.fenum.qual.SwingVerticalOrientation;

public class FlowBreak {
    static @SwingHorizontalOrientation Object CENTER;
    static @SwingHorizontalOrientation Object LEFT;

    boolean flag;

    @SwingHorizontalOrientation Object testInference() {
        Object o;
        // initially o is @FenumTop
        o = null;
        // o is @Bottom
        while (flag) {
            if (flag) {
                o = CENTER;
                // o is @SwingHorizontalOrientation
            } else {
                o = new @SwingVerticalOrientation Object();
                // o is @SwingVerticalOrientation
                break;
            }
            // We can only come here from the then-branch, the else-branch is dead.
            // Therefore, we only take the annotations at the end of
            // the then-branch and ignore the results of the else-branch.
            // Therefore, o is @SwingHorizontalOrientation and the
            // following is valid:
            @SwingHorizontalOrientation Object pla = o;
        }
        // Here we have to merge three paths:
        // 1. The entry to the loop, if the condition is false [@Bottom]
        // 2. The normal end of the loop body [@SwingHorizontalOrientation]
        // 3. The path from the break to here [@SwingVerticalOrientation]
        // Currently, the third path is ignored and we do not get this error message.
        //:: error: (return.type.incompatible)
        return o;
    }
}