It is amazing what length people are willing to go in the hope of "safety".

Is there anybody out there who successfully build their own product, not via VC or other investments, but on their own time and own money who likes types?

To me it seems that types are something consultants and people who get paid for their time instead of their productivity like. Because it makes things more complex. So to achieve the same task, you can bill more time.

I have not seen anybody successfully build something on their own time, money, risk who like types. If there is someone here, I would love to see it!

On the other hand, I have seen many examples of lean code like the following turning into successful life style businesses and companies:

https://gist.github.com/nikcub/3833406

Yes, me. I develop an IDE for Clojure code which is a mix of Clojure and Kotlin. I like both, but what I like about Clojure is the interactive programming, not the lack of types. If there were a statically typed Clojure I’d be all over it.

There's no Typed Clojure, still? I seem to remember people porting Typed Racket to Clojure; a quick search gives me core.typed[1] and typedclojure[2]. There's an example[3] looking like this:

    (t/ann hello-world-error [t/Int :-> t/Str])
    (defn hello-world-error [a] (inc a) ;#"Simplified a bit")

which looks like Typed Racket, where you'd get:

    (: hello (Number . -> . String))
    (define (hello num) (add1 num))

(both definitions are rejected at compile time; in Racket, it works in the REPL, too, not sure about Clojure)

...and Typed Racket is a really powerful type system (see refinement types[4]). So, I thought it's just a matter of time for Clojure to get to that level of power and support. It should be much easier to do this to Clojure than to Ruby, given that you have a working example of how to do it well. So I'm really surprised Clojure isn't gradually typed by now, with most of the code being annotated and type-checked at compile time.

[1] https://github.com/clojure/core.typed

[2] https://github.com/typedclojure/typedclojure

[3] https://github.com/typedclojure/typedclojure/blob/main/examp...

[4] https://docs.racket-lang.org/ts-reference/Experimental_Featu...