import org.checkerframework.checker.nullness.qual.*;

public class PolymorphismArrays {

    public PolymorphismArrays(String[][] elts) {
        this.elts = elts;
    }

    public static boolean @PolyNull [] bad(boolean @PolyNull [] seq) {
        // Cannot directly return null;
        // :: error: (return.type.incompatible)
        return null;
    }

    public static boolean @PolyNull [] slice(boolean @PolyNull [] seq, int start, int end) {
        // Know from comparison that argument is nullable -> also return is nullable.
        if (seq == null) {
            return null;
        }
        return new boolean[] {};
    }

    public static boolean @PolyNull [] slice(boolean @PolyNull [] seq, long start, int end) {
        return slice(seq, (int) start, end);
    }

    public static @PolyNull String[] intern(@PolyNull String[] a) {
        return a;
    }

    // from OneOfStringSequence.java
    private String[][] elts;

    @SuppressWarnings("purity") // ignore, analysis too strict.
    @org.checkerframework.dataflow.qual.Pure
    public PolymorphismArrays clone() {
        PolymorphismArrays result = new PolymorphismArrays(elts.clone());
        for (int i = 0; i < elts.length; i++) {
            result.elts[i] = intern(elts[i].clone());
        }
        return result;
    }

    public void simplified() {
        String[][] elts = new String[0][0];
        String[][] clone = elts.clone();
        String[] results = intern(elts[0].clone());
    }

    public static <T> int indexOf(T[] a) {
        return indexOfEq(a);
    }

    public static int indexOfEq(@PolyNull Object[] a) {
        return -1;
    }
}