It appears to be a bug. It only occurs if:
- Your main source file has a .ino file extension
- You have a project.properties file
- You are targeting system firmware 0.6.0 or later
If any of those conditions is not true, then you'll get the correct error messages as you'd expect.
For example, you can rename your source file to have a .cpp file extension instead of .ino and add to the top:
Or if you are not using any libraries, you can remove the project.properties file.
I'm not sure how long it will take for a bug fix, but either of those workarounds, or using the CLI, can be used to work around the problem for now.
You can track the status of this issue here.