Is there any simple way to manipulate kotlin sources during compile time? Something similar to groovy AST Transformers
We do not provide such an API yet, and I don't think it will ever be as easy as in Groovy.
Why is so hard? Is that becuase kotlin is statically typed?
One difference from Groovy is indeed that loading compiler plugins would not be as easy in Kotlin because of its static nature. But despite all and any technicalities I do not think that functionality of this sort should be too easily accessible for non-scripting languages: too many ways to create subtle problems.