Ad-Hoc Union: Skip generation of Value property

[thomashilzendegen]

It would be nice to skip the generation of the Value property of an ad-hoc union. It could be triggered by SkipValueMember in the attribute.

[PawelGerr]

Thanks for the suggestion. Which of the two do you actually need?

a) The Value property is not generated at all. The union then has no object-typed accessor, and the current value is reachable only through Switch, Map and the AsTx properties.

Note that the generated code itself reads the current value in several places, namely the runtime metadata (Metadata.AdHocUnion.GetValue, ConvertToValue and ConvertToValueExpression) and the default callback of SwitchPartially. Without the property, the body of Value (the switch over the discriminator) gets inlined into each of those places.

b) The Value property is still generated, but with a non-public access modifier, so it disappears from the public API surface while staying available inside the type. This would become a setting along the lines of ValueMemberAccessModifier.

It would also help me to know the underlying goal, for example keeping the public API small, avoiding the boxing of value type members, or pushing consumers towards exhaustive pattern matching.

[thomashilzendegen]

I would like to implement it on my own, because my use case is a "MaybeOf" which is a non-null T (by design) and a Null marker. And the Value should return T? by coalescing to the nullable T in case of the Null marker (e.g. using the Switch method).

I would opt into b) and the possibility to rename the member.