Squid VS klister

In the video, the presenter says he doesn't know any other system with "type-aware hygienic macros". You may want to have a quick look at Scala 3, which also has such a system. See, for instance, this paper and also the precursor work by myself for Scala 2: https://github.com/epfldata/squid#publications

Yeah, that project is pretty much at the bottom of my list, unfortunately. My top projects these days are mgmt, klister, recursion-schemes, and hint... And that's already too much!

case is a special form, ie a bit of core syntax, but, interestingly, data is not. (It is presumably a macro; typechecking is actually done as a part of macro expansion.) The syntax remains pretty uniform. Or, in Klister, type ascription is done via normal S-expression syntax with a form called the, as (the $type $expression); again, the syntax is uniform.

Shameless plug: we don't have that problem in Klister, because our equivalent to main is a run macro which runs an IO action, and your alternate prelude can define its own run macro which expects an IO action from your alternate prelude.

Klister is very similar to Hackett, but implemented in Haskell instead of Racket, and my most recent PR is from 20 days ago, if that's the metric which counts for you. Still very much of a WIP though.

You might be interested in Klister: https://github.com/gelisam/klister

I've now also found an implementation for klister, which is meant to interleave type checking with macro expansion.

In Klister, which already has Scheme-like macros and Haskell-like types (polymorphism, algebraic types and higher-kinded types, but not yet fancier types like RankNTypes and GADTs), our plan to get the best of both worlds (lexical syntax and typed ASTs) is to separate parsing from macro evaluation. That is, users write their programs using the surface syntax of s-expressions, parsers parse those into typed ASTs, and macros are typed by the type of the ASTs they receive as input and produce as output. At this stage this is only a research idea, I don't know if that's going to work out yet, but I hope so!