Transition to implementation instead of created interface in Xcode with Swift

Question

When navigating to a definition using ctrl-cmd-jXcode, I often get a message with a generated interface for a method instead of the actual implementation. How can I get to the actual implementation? I need to manually find the file / implementation manually, which is very cumbersome.

For example, when viewing RxSwift , if I do ctrl-cmd-j, and when you call subscribeNext, I get a message generated interface file that has only the signature of the method: public func subscribeNext(onNext: (Self.E) -> Void) -> Disposable. However, I know that real life is in mode RxSwift/Observable+Extensions.swiftand I have to manually go to this file.

How can I get out of this crazy train?