Recently I found a case where rust's type inference fails for collections of trait objects. Here an example: use std::fmt::Debug; #[derive(Debug)] struct D1; #[derive(Debug)] struct D2; fn debug_vec() -> Vec> { // compiler: hmm, I don't know what type this is. Let's see how this one // unfolds. let mut v = Vec::new(); // compiler: got it, v must be Vec>! v.push(Box::new(D1)); // compiler: gosh darn it, this is no Box add...
