This covers a lot of ground! The author is interested in concurrency, in particular coroutines. They follow a standard approach of PL research to extend a lambd

This covers a lot of ground! The author is interested in concurrency, in particular coroutines. They follow a standard approach of PL research to extend a lambda calculus, discussing typing and compilation. This will seem academic but there are certainly many PL researchers who have deep expertise in compiler design and implementation and who also deeply care about communicating these ideas in a precise, formalized manner. To put this in perspective: even after so many years, decades of research, industry and hobby projects turned million of professional users (before thinking about a type system)... the question of exposing concurrency to programmers is far from settled even if it is so important. There are many approaches and different perspectives on what matters more. Formalizing these approaches has likely been done before, but in practical terms we don't care about abstract properties but about performance. That is why I like the article, implementation concerns are important, but the ability to fully specify behavior is also important. Keep it up.