Yes, you are right that in a literal sense the port is not exact. Primarily, I wanted to have the freedom to use that trait parameter type as a building block f

Yes, you are right that in a literal sense the port is not exact. Primarily, I wanted to have the freedom to use that trait parameter type as a building block for other types if I wished to. See e.g. my 'Graph' implementation.[1] In it, I pass in the type of the vertex as a trait type parameter 'A'. In the 'Graph[A]' trait I also have an abstract type 'E' to represent the edge. 'E' is used in a couple of the methods. Later I define a more specialised 'MapGraph' trait and refine the type 'E' to be a pair of 'A's. I couldn't have done this if I wasn't passing in the 'A' as a type parameter. This leads me to believe that all things considered you get more flexibility from always using type parameters, not to mention somewhat better signal-to-noise in the code (getting rid of all the method type params), and also being able to use 'val's. [1] https://github.com/yawaramin/scala-modules/blob/8df0ec516629b6293a08311805796a0bd78bbc17/Modules.scala#L8 https://github.com/yawaramin/scala-modules/blob/8df0ec516629...