I will mention it as a important alternative in the RFC. Changing a type to non-Copy is a massive backcompat problem due to the change in the semantics of assignment and binding in general.
I think there are two important points which make me lean towards automatically applying to not making Reinterpret opt-in:
- Adding a private field to a struct with all public members is already non-backcompat because you’re making the ‘constructor’ private: i.e. I won’t be able to write
MyStruct { field1: 10, field2: "asdf" } anymore. Therefore, if you want to leave the door open to private fields, you’ll have to add a dummy private field e.g. _dummy: () anyway.
- If you buy (1) and accept that a
Public type has already commited to staying that way, then applying Reinterpret without explicit opt-in feels like a small leap: all the functions defined on a Reinterpret type could be manually implemented with safe code. They’re just fancy ways of setting the values of public fields.
That said, I’m sympathetic to backcompat worries, so, like I said, I’ll make sure this gets the right amount of space in the RFC.
