I'm trying to understand #![feature(specialization)] vs. #![feature(min_specialization)] to inform the design of my types, but I haven't been able to find any novice-accessible documentation. How do the two differ?
Specifically, I expected the following (playground) to be straightforward specialization, but it does not work with min_specialization. Why not?
#![feature(min_specialization)] trait A {} trait B: A {} struct Sa; impl A for Sa {} struct Sb; impl A for Sb {} impl B for Sb {} trait X { fn method(&self); } impl<T: A> X for T { default fn method(&self) { println!("default"); } } // error: cannot specialize on trait `B` // --> src/main.rs:29:13 // | // 29 | impl<T: A + B> X for T { // | ^ impl<T: A + B> X for T { fn method(&self) { println!("specialized"); } } fn main() { Sa.method(); Sb.method(); } 4 posts - 3 participants
