checker/tests/nullness/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)
    @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)
    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;
  }
}