TehPers

If in PHP or JS I make a change, hit F5, and get an error, that’s not any better than the IDE already showing it beforehand.

This is even worse because it can happen in prod without you ever triggering this case. For some projects, it doesn’t matter because the impact of a bug is small. For most, you put a subpar, buggy experience in front of your users, waste more time looking for the cause and debugging later with upset users, and at worst cause actual damages (depending on the project anyway).

You can’t create a subset of an enum directly, but splitting this up into multiple types works. You can have FunctionAError with errors that function can produce and a variant for your common errors, and FunctionBError which is similar:

#[derive(Debug, Error)]
enum MyErrorCommon {
    #[error("bad value ({0})")]
    MyErrorCommon(String),
}

#[derive(Debug, Error)]
enum FunctionAError {
    #[error("error a")]
    MyErrorA,
    Common(#[from] MyErrorCommon),
}

// and same for FunctionBError

The try operator (?) will automatically use From impls to convert errors for you as well. If a function returns a result containing MyErrorCommon in your function and you use ? on it, it gets converted to that function’s error type for you. thiserror generates the From impl for you if you use #[from].

Types aren’t unit tests. Unit tests only test a discrete set of inputs and outputs for correctness, and can miss cases that aren’t tested for.

In sound type systems, they are closer to formal verification. The compiler guarantees the properties you expect of the type hold.

As for the rest of the article, do what works best for you in your projects, but if I need to work with you, I’m going to ask for types. I need to know what types the interface expects to receive. Names are not enough. Document them, use type hints, whatever, just put them somewhere because I’m not psychic and I don’t know what you thought about when writing the function.

There’s a lot of bold claims being made. No segfaults, no memory leaks, etc. I’m curious to see how that’s implemented.

Also:

it’s safer than Rust because it lacks an “unsafe” keyword

lol

It’s hard to tell what it is you’re trying to do here, but maybe Option isn’t the right type? To me it feels like you’d want to return a type like Vec or an iterator.

I would recommend looking at some of the iterator functions to do this. You could look at filter_map, collect, and fold/try_fold and see if any of those help you here.

If you’re hoping for the standard lib to have things built on evolving standards and ecosystems like HTTP clients, then I doubt that will ever happen. There are plenty of examples of why that would be a terrible idea (urllib, std::regex, etc).

Sometimes when I don’t leave comments like that, I get review comments asking what the line does. Code like ThisMethodInitsTheService() with comments like “what does this do?” in the review.

So now I comment a lot. Apparently reading code is hard for some people, even code that tells you exactly what it does in very simple terms.