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What Scala features can't you use?

• dtech 9y ago
  implicits mainly, these are objects looked up by the compiler for various purposes e.g. Typeclasses, or how to serialize a specific object to JSON. The Scala 2.8-2.12 collection library was impossible to call from Java, one of the reasons for an upcoming redesign in 2.13.
• ivan_gammel 9y ago
  Real example from my experience: you use a Scala Map and pass it to something like FreeMarker, expecting that it will work like Java Map there. It will not and depending on your test coverage and SQA capabilities, you may notice it very quickly or very late (you'll get no compile error, since template engines usually accept generic objects and then analyze their type via reflection).
  • AzzieElbab 9y ago
    Why would you expect this to work? In fact given that API a map from another java library(say guava) would have crashed you just as well
    • ivan_gammel 9y ago
      Well, I wouldn't even try to have a source code written in two different languages in the same component. But I've seen this problem in someone else's real code, which was probably caused by a not really well-thought migration of Java code to Scala. Basically, a developer replaced one Map with another, fixed all the places where API was different on source code level and a number of tests. However, interoperability issues like this one may be hard to catch in general (even with good test coverage and regular code reviews) and they show the complexity of the problem, that requires certain level of development skills and discipline to do it right.
      • AzzieElbab 9y ago
        You are right, this particular example is more of case against reflection rather than anything else. Having said that, Scala maps actually are tricky to use from java. In general scala does a better job in compatibility when it comes to reuse of java code from scala, but not the other way around