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fix(result): Result<T> hash collision

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A success result wrapping a value whose GetHashCode is 0 (e.g. Result<int>
with 0) collides with a failure result, both hashing to 0.
This commit is contained in:
Louis Seubert 2026-07-12 18:32:16 +02:00
commit fbbe94bfa8
Signed by: louis9902
GPG key ID: 4B9DB28F826553BD
3 changed files with 75 additions and 3 deletions
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70
src/request.result.tests/ResultEqualityTests.cs
View file

@ -166,11 +166,28 @@ internal sealed class ResultEqualityTests
}
[Test]
public async Task I_can_get_hashcode_and_get_zero_for_failure()
public async Task I_can_get_hashcode_and_get_non_zero_for_failure()
{
var result = Prelude.Failure<int>("error");
await Assert.That(result.GetHashCode()).IsZero();
await Assert.That(result.GetHashCode()).IsNotEqualTo(0);
}
[Test]
public async Task I_can_get_hashcode_and_not_collide_non_generic_success_and_failure()
{
await Assert.That(Prelude.Success().GetHashCode())
.IsNotEqualTo(Prelude.Failure("error").GetHashCode());
}
[Test]
public async Task I_can_get_hashcode_and_not_collide_success_value_zero_with_failure()
{
var success = Prelude.Success(0);
var failure = Prelude.Failure<int>("error");
await Assert.That(success.Equals(failure)).IsFalse();
await Assert.That(success.GetHashCode()).IsNotEqualTo(failure.GetHashCode());
}
[Test]
@ -199,4 +216,53 @@ internal sealed class ResultEqualityTests
await Assert.That(a.Equals(b)).IsFalse();
}
[Test]
public async Task I_can_use_equality_operator_and_get_false_for_success_and_failure()
{
var success = Prelude.Success(2);
var failure = Prelude.Failure<int>("error");
await Assert.That(success == failure).IsFalse();
await Assert.That(success != failure).IsTrue();
}
[Test]
public async Task I_can_use_equality_operator_and_get_true_for_successes_with_equal_value()
{
await Assert.That(Prelude.Success(2) == Prelude.Success(2)).IsTrue();
await Assert.That(Prelude.Success(2) != Prelude.Success(3)).IsTrue();
}
[Test]
public async Task I_can_use_equality_operator_and_compare_result_to_value()
{
await Assert.That(Prelude.Success(2) == 2).IsTrue();
await Assert.That(Prelude.Success(2) != 3).IsTrue();
await Assert.That(Prelude.Failure<int>("x") == 2).IsFalse();
}
[Test]
public async Task I_can_equal_object_and_get_false_for_null()
{
object result = Prelude.Success(2);
await Assert.That(result.Equals(null)).IsFalse();
}
[Test]
public async Task I_can_equal_object_and_get_false_for_wrong_type()
{
object result = Prelude.Success(2);
await Assert.That(result.Equals("not a result")).IsFalse();
}
[Test]
public async Task I_can_equal_object_and_get_true_for_boxed_equal_result()
{
object result = Prelude.Success(2);
await Assert.That(result.Equals(Prelude.Success(2))).IsTrue();
}
}

7
src/request.result/Result.Equality.cs
View file

@ -181,7 +181,12 @@ public partial class Result<T> : IEquatable<Result<T>>, IEquatable<T>
return comparer.GetHashCode(result.Value);
}
return 0;
if (result is { IsSuccess: true, Value: null })
{
return 0;
}
return result.Error?.GetHashCode() ?? 0;
}
}