Right this is what I tried to do but unfortunately trying to mark everything immutable in Typescript leads to some very unergonomic type signatures. Hopefully this can improve in the future.
Could you show an example of what you mean? Not sure how not mutating data would lead to more unergonomic type signatures, I'm sure an example would help me understand. Although it wouldn't surprise me TypeScript makes things harder.
You are polluting every variable signature with `readonly`. This also can create cascading effects where making one function accept only readonly variables forces you to declare readonly elsewhere as well. Quite similar, in a way, to Rust.
If I have a complex structure MyStruct that I make recursively readonly it doesn't show up in the IDE as DeepReadOnly<MyStruct> or something like that. It shows up as a huge tree of nested readonly declarations, so the original type is highly obscured.