Allow unsized types for OnceBox and OnceRef

Question

Allow unsized types for OnceBox and OnceRef

neoeinstein opened this issue a year ago · comments

Because both of these types are held behind a reference, they should be able to accept unsized types, allowing for things like OnceBox<str> or OnceBox<'static, str>.

Alex Kladov · Answer 1 · Mon Mar 20 2023 05:21:24 GMT+0800 (China Standard Time)

I am not sure that'll work: we use pointer CAS in the implementation, so we need the pointer to be a narrow one.

Andrew Walbran · Answer 2 · Fri Apr 14 2023 23:42:19 GMT+0800 (China Standard Time)

Being able to use OnceBox<dyn MyTrait> or OnceRef<dyn MyTrait> would also be useful, and seems to be blocked for the same reason.

Alex Kladov · Answer 3 · Sun Jun 04 2023 19:23:49 GMT+0800 (China Standard Time)

Yeah, I don't think this could work