Fix S4035: FP for abstract declarations

[Corniel]

Description

public abstract class ValueObject<T> : IEquatable<T> where T : ValueObject<T>
{
    public abstract bool Equals(T other); // compliant
}

public class MyValueObject : ValueObject<MyValueObject>
{
    public override bool Equals(MyValueObject other)
    {
        return RefrenceEquals(this, other); //non-compliant
    }
}

public sealed class MySealedValueObject : ValueObject<MySealedValueObject >
{
    public override bool Equals(MySealedValueObject  other)
    {
        return RefrenceEquals(this, other); //compliant
    }
}

To me, this should not raise the this concern on the abstract class with an abstract method. The implementing class should, if not sealed.

Related information

• Rule S4035: Classes implementing "IEquatable<T>" should be sealed #461
• 7.11.0.8083
• Visual Studio 15.9.7

[christophe-zurn-sonarsource]

Hello @Corniel,
Indeed, for the same reason Rule S4035 does not raise an issue for virtual Equals method, it should also not raise issue for abstract Equals method.

    public abstract class ValueObject<T> : IEquatable<T> where T : ValueObject<T>  // FP
    {
        public abstract bool Equals(T other);
    }