It should be the simplest possible situation, none of the Swift code needs to be public and it also does not need to access the Objective-C++ code. Problem is of course that the Swift compiler insists on reading the umbrella header which references header files that include C++ code. In order to make it build I can conditionalize the umbrella header includes on __cplusplus but that leads to a lot of warnings about the umbrella header not including public files. And there doesn't seem to be a selective way to silence those warnings. Any way to tell the Swift compiler that it should not care about the umbrella header?