lint against using a binding whose name is prefixed with an underscore

[oli-obk]

Prefixing an underscore to a binding is done to silence unused warnings. This makes it easy to recognize explicitly unused bindings by their name, and still have a name that tells you something about the binding. In case you start using the binding, you should remove the underscore.

[Manishearth]

I like this idea, but I don't know how to do it without duplicating liveness. Perhaps exprusevisitor.

[oli-obk]

Maybe there's another way. Look for ExprPath where the name starts with an underscore?

[Manishearth]

I'm an idiot. Thanks.

[oli-obk]

glad I'm not alone ;)

[llogiq]

Welcome to the club. 😜

[devonhollowood]

I could do this if someone is willing to mentor.

[oli-obk]

@devonhollowood I'll try. What do you need? I'm reachable on irc if you need real-time-feedback

For variables you probably just need an EarlyLintPass that implements check_expr and in case the Expr is a path or a struct field indexing, checks whether the last element of that path starts with an underscore.

[Manishearth]

Or a local variable.

You can do these checks with the def_map that comes with the cx.tcx. But it needs to be a LateLintPass (stick it in misc.rs I guess). Feel free to ping me if you need more help!

[oli-obk]

do we need the definition? Maybe for ensuring that the error is only reported once?

[Manishearth]

No, for ensuring that it is indeed a variable, not a function or something 😄