It's not an error in your code. There has been a very recent commit to the repo, most likely initiated by your comment:
> Fix various minor things that stopped compilation > > This tries to address a couple issues with compiling for 2.0.0. Unfortunately > the "implicitDeref" experimental is now gone, which means that even with > these changes it doesn't compile under Nim 2.0.0 (at least not the genui > controlgallery demo). This will need some internal changes to make things > work again. You can still try it with nim 1.6 .
