What does the @elidable annotation do in Scala, and when should I use it?

Question

I\'ve noticed in some of the scala library code, notably Predef, there is code like:

/** Tests an expression, throwing an `AssertionError` if false.         


        

Answer 1

Actually, expressions can't just disappear, because they have a result. When you elide an invocation of a method of result type Boolean, you wind up with false, and so on.

There was an issue a few months after this question was posted to settle what eliding Nothing does. The outcome was to elide to ???.