syntax - Private scoping with square brackets (private[...]) in Scala

Question

I've come across the following syntax while looking through the Gatling source code:

private[http] def build = {
  // ...
}

What is the syntax inside square brackets?

When I click through it in my IDE it is an alias to a fully qualified package (com.excilys.ebi.gatling.http) but I can't find where that alias was defined.

Answer 1

See the scala reference, specifically, chapter 5.2. Some excerpt:

The private modi?er can be used with any de?nition or declaration in a template. Such members can be accessed only from within the directly enclosing template and its companion module or companion class (§5.4). They are not inherited by subclasses and they may not override de?nitions in parent classes.

The modi?er can be quali?ed with an identi?er C (e.g. private[C]) that must denote a class or package enclosing the de?nition. Members labeled with such a modi?er are accessible respectively only from code inside the package C or only from code inside the class C and its companion module (§5.4). Such members are also inherited only from templates inside C.