Smart programmers are are not coding thousands of lines of code every day. There's so much more to in software engineering other than coding, that's why senior engineers spend less time writing code than juniors.
If a slow typer is using a auto-completer, he's not learning to type faster.
If auto complete fails, then the slow programmer will need to invalidate the code first, and then type it anyway.
All in all - maybe it's impressive AI research project, but I don't see it as a useful product.
The difficulty with high flexibility is that the expressions become very domain-specific very quickly, creating the challenge of learning the new abstractions. So one isn't just a LISP developer, one knows how to write in the specific forest of macros that have been built up around one specific problem domain. The end result is code that means nothing to a reader who doesn't have a dense forest of macro definitions in their brain (at least in this era, their IDE will likely helpfully pull up the macro definitions with a mouse-over or cursor-over gesture!).
Contrast with this approach, where the complexity of abstraction is being baked into the lower-flexibility language. The code is less dense, and that's a tradeoff... But grab any 10 developers off the street with experience in that language and have them read it and 8 of them will likely be able to tell you with some accuracy what the code is doing. Not a trick I've seen possible with even very experienced LISP developers on a codebase they've never seen before.
... and, of course, being able to grab a random 10 developers off the street and have 8 of them up-to-speed in no time at all is crack cocaine to big businesses with large and complex systems maintained by dozens, hundreds, or thousands of people.
Do you think there's a risk that a tool like this could lead to an explosion of the size of codebases written in these languages? It's great that programmers can be freed from the need to write boilerplate but I fear that burden will shift to the need to read it.
I can imagine this being very useful in helping to type out what I consider to be „mechanical noise“: Things that you have to type out to satisfy an expression rather than to convey semantics.
A good example of how this type of noise manifests:
Observe two programmers, both being similarly strong in terms of many concepts except for mechanical expertise. One uses the editor as an extension of their body, it’s beautiful to watch, the other stumbles awkwardly over the code until it’s finished. You can observe the latter in programmers who are very smart and productive, but they either didn’t train their mechanics deliberately or maybe they lack that kind of baseline eye hand coordination.