[olivermuty]

Elixir dev here, just to put the context in place first hehe.

Couldn’t that thing be typed as the web format? A nested set of string props with either string or number types in the leaves.

Then use those types to traverse and pull into «real» types?

I like to put structured data into structs in elixir too and the above is essentially what I would do in Elixir.

I don’t know rust well enough to see if I am missing some nuance

[miroljub]

You can do that in every language, even in Java 1.0, by just using a hash maps of objects, and cast those objects to whatever you like at runtime before accessing them.

But then, you are basically throwing out your static type checks and just using it as a dynamic language, but with much more verbosity, cruft and additional ways to should yourself in the foot.

[josephg]

Yep. It’s awkward. The language fights you every step of the way and it becomes hard to read and write your code. x.foo = 6 becomes x.set(String(“foo”), Num(6));. When you read that value back you’ll need to unwrap the type you expect before you can do anything with it. It would be utterly miserable. You’d be much better off just using Python, JavaScript or Ruby.

You also lose all of the performance benefits typing brings, and gain nothing in return. In JavaScript land, V8 moves heaven and earth to guess what your types are and optimistically compile your code behind the scenes assuming its type annotations are correct. Then it dynamically deoptimises and reoptimises at runtime with that new information, while your program runs. As well as being ugly, the equivalent “dynamically typed” rust program would have none of V8’s smarts. It would run dog slow compared to normal rust and still way slower than the (much cleaner) JavaScript equivalent.

Like wood, programming languages all have a grain. If you program in harmony with the language’s design, everything will seem easy. Compiler errors make sense. The standard library will seem useful and well designed. Program against the language’s design and you’ll hate every minute of it.