Asserts.java

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

public class Asserts {

    void propogateToExpr() {
        String s = "m";
        assert false : s.getClass();
    }

    void incorrectAssertExpr() {
        String s = null;
        assert s != null : "@AssumeAssertion(nullness)"; // error
        s.getClass(); // OK
    }

    void correctAssertExpr() {
        String s = null;
        assert s == null : "@AssumeAssertion(nullness)";
        //:: error: (dereference.of.nullable)
        s.getClass(); // error
    }

    class ArrayCell {
        @Nullable Object[] vals = new @Nullable Object[0];
    }

    void assertComplexExpr(ArrayCell ac, int i) {
        assert ac.vals[i] != null : "@AssumeAssertion(nullness)";
        @NonNull Object o = ac.vals[i];
        i = 10;
        //:: error: (assignment.type.incompatible)
        @NonNull Object o2 = ac.vals[i];
    }

    boolean pairwiseEqual(boolean @Nullable [] seq1, boolean @Nullable [] seq2) {
        if (!sameLength(seq1, seq2)) {
            return false;
        }
        if (ne(seq1[0], seq2[0])) ;
        return true;
    }

    @EnsuresNonNullIf(
        result = true,
        expression = {"#1", "#2"}
    )
    boolean sameLength(final boolean @Nullable [] seq1, final boolean @Nullable [] seq2) {
        // don't bother with the implementation
        //:: error: (contracts.conditional.postcondition.not.satisfied)
        return true;
    }

    static boolean ne(boolean a, boolean b) {
        return true;
    }

    void testAssertBad(boolean @Nullable [] seq1, boolean @Nullable [] seq2) {
        assert sameLength(seq1, seq2);
        // the @EnsuresNonNullIf is not taken from the assert, as it doesn't contain "nullness"
        //:: error: (accessing.nullable)
        if (seq1[0]) ;
    }

    void testAssertGood(boolean @Nullable [] seq1, boolean @Nullable [] seq2) {
        assert sameLength(seq1, seq2) : "@AssumeAssertion(nullness)";
        // The explanation contains "nullness" and we therefore take the additional assumption
        if (seq1[0]) ;
    }

    void testAssertAnd(@Nullable Object o) {
        assert o != null && o.hashCode() > 6;
    }

    void testAssertOr(@Nullable Object o) {
        //:: error: (dereference.of.nullable)
        assert o != null || o.hashCode() > 6;
    }
}