It's probably worth noting that the majority of the development on that library was done on April 1st 2019.
https://hackage.haskell.org/package/base-4.14.0.0/docs/src/D...
Also notice that Dynamic is in the Haskell Package Repository's "base" package, described as containing "Basic libraries", not part of an ancillary area for user-contributed libraries:
https://hackage.haskell.org/package/base-4.14.0.0
There exist type systems of which great grandparent is an accurate description (the most well-known of which is probably that used by Typescript) but the type system of, e.g., Haskell, Ocaml or Rust is not it.
(Now I am getting curious what specific programming language's type system great grandparent had in mind.)
https://hackage.haskell.org/package/dynamic
Which is an entirely different package, and the relevant types are entirely different. Only the name is the same. The `dynamic` package does indeed appear to be an april fools joke.
The Dynamic type in base is about runtime reflection, which is occasionally useful but not something that comes up often and not really about rapid prototyping.
>The Dynamic type in base is about runtime reflection, which is occasionally useful but not something that comes up often
It is not something that comes up often, but since I am used to languages like Javascript or Scheme, when it does come up, figuring out how to do it in Haskell, e.g., satisfying the monomorphic restriction, has occasionally diverted my focus away from the problem to be solved for hours while I learn more about Haskell's type system.
But yeah, what I just wrote is in no way inconsistent with the comment I initially replied to, namely,
https://news.ycombinator.com/item?id=23795687
so I am going to admit that my comments in this thread have not exactly improved the level of discourse.