We're also discussing a @noImplicitCopy attribute that can be applied to normally-copyable things to get fully manual copying behavior. Whether a type is copyable or not is a fundamental part of its representation, so it wouldn't work well to have types sometimes be copyable or not, so I think that sort of annotation, to tell the language not to implicitly take advantage of copying even if a copy operation is available, is a better way to go for the sort of situation you describe. The pitch that's up only discusses @noImplicitCopy as a variable modifier, but I think we could support it for scopes as well, and one of those scopes could be "the entire module". However, one thing to work out with these scoped noImplicitCopy modifiers is whether there should be exceptions to allow some types to always be copyable. You probably never really care if an Int gets implicitly copied, for instance, and it would be annoying to have to think about copying at that level.
1 Like