I don't work on the language, but I think building a compiler in Go (or C) is a pain in the ass compared to using a language that has discriminated union types, and based on the aesthetics of the language, the authors probably agree with me. The language is styled enough like Rust to make it seem like this is for "rust people" more than "Go people" anyways – I think if this was targeting Go people, it would use the native Go syntax for things like import (here replaced with "use") and adding methods, here replaced with "impl ..."