This post is inspired by this text by Gilad Bracha. I recommend that you read it before reading this blog post. The idea of Shadow Worlds is that people keep inventing these constructs that are powerful enough that you want to use them as programming languages, but they are not powerful enough to have the features of high level programming languages that make programming enjoyable.
Before reading that blog post I knew that I wanted a macro system for my language. Looking at my old notes I had written down that a macro system is necessary, and that templates are not enough. However I wanted a type safe macro system from modern languages like Nim or Rust. Gilad Bracha’s blog post made me realize that you actually never want macros because they are just another Shadow World. Instead you want to do everything in your high level language.