Is use of chrono an example where extern crate statement is still required? I'm getting message that it is but was wondering why. The documentation mentions something about sysroot modules as still requiring them. What are those modules and is chrono one of those?
Also there is this, but I figured since you have to get chrono from crates it's not one of those. Could a diffinitive list be created and if so how?
Additional crates that ship with
rustc, such as
test, are not automatically included with the
--externflag when using Cargo. They must be brought into scope with an
extern cratedeclaration, even in the 2018 edition.