Update macros context code to use whitebox context

[nogurenn]

Closes #1710

Is there a one-liner/short code I can use to illustrate the difference of whitebox and blackbox contexts? Something like

funcThatShowsDiff(macro blackImpl)
funcThatShowsDiff(macro whiteImpl)

[SethTisue]

The underscore on _final is peculiar, I think. I understand that it's there to avoid the clash with the keyword final, but I think it would be better to avoid the clash some other way. I'll add a commit with a different renaming.

re: one-line examples, I can't think of anything offhand; I think the PR is mergeable regardless. I like what you did by adding a link.

[SethTisue]

thank you!

[nogurenn]

I usually do _foo for specifically localized implementations where a foo name makes sense in the scope also, treating _foo as like a temp variable. I forgot how I came up with it, or where I picked it up. I remember thinking it's better than val someVagueTempVariableName to me. Maybe I got it from another language that implements _foo for internals, and exposes foo in its interfaces?

// an example whose form makes more sense in code like nodejs
val persons = {
  val data = db.run(personsQuery.result)
  val _persons = ... // code further processing `data`
  
  return _persons
}

[SethTisue]

another language that implements _foo for internals, and exposes foo in its interfaces?

I see that in Scala codebases too, including my own.

In this context I didn't consider it actually wrong, just unnecessarily distracting.

For avoiding a clash with a keyword, note that Scala also allows:

val `final` = ...

[nogurenn]

No problem from my end! Just thought it's a nice reminder to re-assess my coding practices from time to time