No compilation errors but AS Canary 5 shows this error after upgrade to Compose alpha12.

I'm 99% sure this is https://youtrack.jetbrains.com/issue/KT-44563 It was a regression that we identified+fixed just days before the 1.4.30 release, so it probably didn't make it into the 1.4.30-rc build that I think studio is using. This should be fixed when studio upgrades to 1.4.30-stable.