Treat more constructors as pure in the optimizer

[retronym]

e.g. scala.Some (https://github.com/scala/scala/compare/2.12.x...retronym:topic/pure-some?expand=1)

Perhaps also:

• Left / Right / Success

@lrytz WDYT?

[lrytz]

Sure - is there a specific use case?

[retronym]

Nothing very scientific, I just noticed the possibility when demoing call-site inline annotations on gitter:

scala> class Inline2 { def test = (Some(1).isEmpty : @inline) }
defined class Inline2

scala> :javap -c Inline2#test
  public boolean test();
    Code:
       0: new           #17                 // class scala/Some
       3: iconst_1
       4: invokestatic  #23                 // Method scala/runtime/BoxesRunTime.boxToInteger:(I)Ljava/lang/Integer;
       7: invokespecial #27                 // Method scala/Some."<init>":(Ljava/lang/Object;)V
      10: iconst_0
      11: ireturn

[lrytz]

Longer-term I'm hoping to get a more generic solution, probably by supporting @inline on classes (Some), or maybe some heuristics / class analysis