Scala 2.12 supports Single Abstract Method (SAM) syntax like Java 8. Using this would lightly simplify a lot of code where we define an anonymous inner class. E.g.
There's a small improvement to readability, and probably a tiny benefit at runtime as these become lambdas in the JVM, not inner classes that have to be compiled and instantiated. (There's also a very small reduction in the chance that those inner classes are accidentally holding references to things we don't want them to.)