castaway | cost downcasting for limited compile

castaway is a Rust library. castaway has no bugs, it has no vulnerabilities, it has a Permissive License and it has low support. You can download it from GitHub.

This is an experimental library that implements zero-cost downcasting of types that works on stable Rust. It began as a thought experiment after I had read this pull request and wondered if it would be possible to alter the behavior of a generic function based on a concrete type without using trait objects. I stumbled on the "zero-cost"-ness of my findings by accident while playing around with different implementations and examining the generated assembly of example programs. The API is somewhat similar to Any in the standard library, but Castaway is instead focused on ergonomic compile-time downcasting rather than runtime downcasting. Unlike Any, Castaway does support safely casting non-'static references in limited scenarios. If you need to store one or more Box objects implementing some trait with the option of downcasting, you are much better off using Any.