Messagepack-csharp: v1.7.3.4, System.ArgumentException: An item with the same key has already been added

[SylphiaWindy]

public class A:B<int>{
    protected override int Id => 10;
}

public abstract class B<TId>{
    protected virtual TId Id => default;
}

Serialize object of A with ContractlessStandardResolverAllowPrivate

[SorenZ]

I've experienced the same issue in my codebase.
Start to study the source code to find out possibles solutions.

[AArnott]

Looks like #582 might fix this or a related issue.

[AArnott]

Confirmed fixed in master.