I am getting a compiler error with latest version of Device OS but not with older versions.
Error version Device OS=3.0.0 rc2.
Earlier version with no error: 1.5.4 rc2
Code: Bluetooth LE | Tutorials | Particle
Since the code is well established and tried many times, I suspect this may be an issue with the compiler. For now, I am using the older version of Device OS compiler.