From my point of view, I think it doesn't provide much information.

[Scala style guide](http://docs.scala-lang.org/style/types.html#inference) mentions

> You should almost never annotate the type of a private field or a local variable, as their type will usually be immediately evident in their value. [...] However, you may wish to still display the type where the assigned value has a complex or non-obvious form.

I don't think this is complex enough to justify specifying the type.