
Wow, what a precise error message. Right-click for more information brought me to a very generic webpage telling me, that I could have probably found a compiler error. Great! First time ever that I discovered a compiler error. But wait: I bing'ed (can you say this?) for the error message, to see if somebody already reported this. BING! Match. And here we go:
The solution was pretty easy and documented here.
I searched my source code and found this line:
Have you noticed the first "=" instead of the ":"? Lucky you! It took me far too much time to discover this typo.
Fixing this typo and the error went away.