Constants.java

import org.checkerframework.checker.interning.qual.Interned;

public class Constants {

    // All but D should be inferred to be @Interned String.
    final String A = "A";
    final String B = "B";
    final String AB = A + B;
    final String AC = A + "C";
    final String D = new String("D");
    final @Interned String E = new String("E").intern();
    final Object F = "F";

    void foo() {
        @Interned String is;
        is = A;
        is = B;
        is = AB;
        is = A + B;
        is = AC;
        is = A + "C";
        is = A + B + "C";
        //:: error: (assignment.type.incompatible)
        is = D;
        //:: error: (assignment.type.incompatible)
        is = A + E;
        //:: error: (assignment.type.incompatible)
        is = is + is;
        is = Constants2.E;
        is = (String) F;
    }
}

class Constants2 {
    public static final String E = "e";
}