Insert inferred type annotation for Scala val/var/def

At the moment, I type in type annotations for public `val`s, `var`s and `def`s in my Scala classes, traits and objects[1] - either by inferring the types of them mentally, or occasionally by hovering over the identifier in Eclipse to find out what the presentation compiler thinks the type should be[2]. How can I conveniently add these type annotations automatically? The purpose of adding in explicit types is to "lock in" the type of a public member of a template, so that if a developer changes the definition of the member in future in a way that results in an incompatible type, they will get a compile-time error unless they deliberately change the type annotation as well. Footnotes: [1] except if they override a member in a supertype and the type should be the same as the type of the overridden member, which is usually the case for overrides in my code. [2] This isn't always correct; the presentation compiler seems to be weak when it comes to members that override members in supertypes.