record generic constraint

[ekgurney14]

Would it be possible in the future to allow record to be a constraint on a generic class/record.
I would like to be able to create a class where I am able to use 'with' record creation on the generic type to promote immutability.
e.g.
``
public interface IValue
{
public int Value {get;init;}
}

public class Api where T : record, IValue
{
public T DoSomething(T item) => item with { Value = 1 };
}

``

[huoyaoyuan]

Records are designed to not be distinguishable with normal classes. This code isn't achievable now, because the Clone method is not constrained.

I'd prefer to achieve things like this with HKT.

[ekgurney14]

Not super familiar with HKT. How would this look when solving my issue?

[huoyaoyuan]

Currently, interface can only constraint on named instance members, and cannot depend on the actual type (no way to represent typeof(this) Clone(). HKT is designed to do more abstractions on types.

[YairHalberstadt]

See #3859, #39 (comment) and #3899 for earlier discussions of this

[ekgurney14]

The key takeaway from those previous discussions is that hopefully the 'with' expression will be usable with classes in c# 10. They eliminating my need from the initial question.