Add an analyzer to prevent the explicit definition of the EqualityContract property, which establishes value-based equality in Records

[egvijayanand]

Even though a reference type, Records exhibit Value-based equality.

For that, it generates the getter only EqualityContract property that returns its actual type info (immutable).

However, this does not prevent it from being manually defined. Perhaps it is an intentional consideration.

To prevent unintentional usage, it would be advisable to implement an analyzer that alerts the user to its implications.

Run the below code for an example. Program is doing what is instructed to perform. Ideally, this should return False as types are incompatible.

I managed to get it working by returning the matching type info, but this can return any type info (say, typeof(decimal)) as it is not linked to the containing type. Therefore, it advisable to add this analyzer as soon as possible.

var origin = new Point2D(0, 0);
var initial = new Point3D(0, 0, 0);
Console.WriteLine(origin == initial);

record Point2D(int X, int Y)
{
    protected virtual Type EqualityContract => typeof(Point2D);
}

record Point3D(int X, int Y, int Z) : Point2D(X, Y)
{
    protected override Type EqualityContract => typeof(Point2D);
}

[HaloFour]

You can suggest analyzers at the following repo: https://github.com/dotnet/roslyn-analyzers

[egvijayanand]

Can this discussion be transferred there? If so, please.

[333fred]

It would be best to open a new issue that follows their templates.

[egvijayanand]

Fine. This can be updated appropriately.