As a library maintainer I need to make the choice of which version to target.

It's easy to accidently use features of a recent rust version, as you can see in this example:

https://github.com/mkmik/slyce/issues/17

I could work around this issue and pin the rustc version in the CI system to avoid regressions, but is it worth the effort since it's likely that this particular user will eventually depend on another library that uses a feature of >1.43 and thus eventually give in and use rustup? I want to be helpful towards users of my library, but I wonder if the most rational choice is to encourage users to upgrade the toolchain more liberally.