Not really, that is solved with aliases. The problem really comes to life when using strongly typed generic functions that must be generic over their return typ

Not really, that is solved with aliases. The problem really comes to life when using strongly typed generic functions that must be generic over their return type. This most notably occurs with Rust iterators. Try writing out the type of this thing explicitly: let pos_nums = v.iter().map(|s| s.parse::<u64>().unwrap()).filter(|n| n > 0); Hint: you literally can't in current Rust because closures have Voldemort types, you can't name their type. And even if you could, the resulting type would be horrendous.