Add no-use-before-define for variables and classes

[svanherk]

Tackling a story we've had sitting around for a while. Having this linting rule would have saved us from a my courses hotfix after we toggled on some very old code triggered by a very specific edge case. Thoughts?

https://eslint.org/docs/rules/no-use-before-define

[dbatiste]

I don't have a strong preference for this. In my view, hoisted variables were always a potential source of bugs. That said, this ought to be less of an issue with ES6 let/const. Adding this rule to the common config may result in some existing projects failing on linting. Is the intention to do a major version bump?

[svanherk]

I don't have a strong preference for this. In my view, hoisted variables were always a potential source of bugs. That said, this ought to be less of an issue with ES6 let/const. Adding this rule to the common config may result in some existing projects failing on linting. Is the intention to do a major version bump?

Yeah we'd have to, core fails in a few places (mostly visual diff tests which declare a const helper at the bottom). But it'd just need to be a minor release since we're still version 0

[dlockhart]

Definitely in favour of this change.