This lint looks for: let mut vec = Vec::with_capacity(len); vec.set_len(len); The suggested replacement is `vec![0; len]`. This is far too opinionated to be a deny-by-default lint because the performance characteristics of the suggested replacement are totally different. I am not convinced that this lint has value beyond what deny(unsafe_code) gives you. Unsafe code is unsafe but please don't deny-by-default lint it if that's the only reason.