Non symmetric == operator in record subclasses overriding EqualityContract

[dariocc]

Hi!

After reading c# 9 records proposal I was experimenting with subclassing records and equality and I found that overriding EqualityContract breaks symmetry of the == operator:

    public record Foo(string Value)
    {
    }

    public record Bar(string Value) : Foo(Value)
    {
        protected override Type EqualityContract => typeof(Foo);
    }
    
    [Test]
    public void TestFooBar()
    {
        Assert.That(new Foo("foo") == new Bar("foo"), Is.True); // Passes
        Assert.That(new Bar("foo") == new Foo("foo"), Is.True); // Fails!
    }

• Is this behavior intended?
• If so, doesn't it limit the usefulness of making it possible to override EqualityContract?

[agocke]

The purpose of the equality contract is to preserve symmetry -- if you override it, you may break symmetry. Sometimes, that may be what the user wants but you're right, it shouldn't be taken lightly!