I'd still like some comment on my idea of making the auto-generated op== available inside a custom definition of Equatable.
That way you can build on the default without the need for an @dontequate memberwise keyword.
I admit it is a little clumsy to make copies first, set the "dontequate" properties to equal values in lhs and rhs, equate and then extend equating some of your calculated properties.
Jan E.