the article says “It’s part of the standard library,” which gets the point across that it doesn’t require any external dependencies but it may be slightly misleading to those who interpret it literally - let-else a language feature, not part of the standard library, the relevant difference being that it still works in contexts that don’t have access to the standard library.

I tend to use Option::ok_or more often because it works well in long call chains. let-else is a statement, so you can’t easily insert it in the middle of my_value().do_stuff().my_field.etc(). However, Option::ok_or has the annoying issue of being slightly less efficient than let-else if you do a function call in the “or” (e.g. if you call format! to format the error message). I believe there’s a clippy lint for this, although I could be mixing it up with the lint for Option::expect (which iirc tells you to do unwrap_or_else in some cases)

I appreciate the author for writing a post explaining the “basics” of rust. I’ll include it in any training materials I give to new rust developers where I work. Too often, there’s a gap in introductory material because the vast majority of users of a programming language are not at an introductory level. e.g. in haskell, there might literally be more explanations of GADTs on the internet than there are of typeclasses

In general I think there is a lack of intermediate Rust material that teaches you common design patterns, idiomatic Rust, and so on.

Even I (someone who's written hundreds of thousands of fairly complex Rust code) learnt about the let-else style solution from this article =).

   const user = getUser() orelse return error.NoUser;

    if (getUser()) |user| {
        // use user
    } else {
        return error.NoUser;
    }

    [lints.clippy]
    all = "deny"
    unwrap_used = "deny"
    expect_used = "deny"
    panic = "deny"
    indexing_slicing = "deny"
    unhandled_errors = "deny"
    unreachable = "deny"
    undocumented_unsafe_blocks = "deny"
    unwrap_in_result = "deny"
    ok_expect = "deny"

The error in question:

> the `?` operator can only be used on `Result`s, not `Option`s, in a function that returns `Result`

It literally tells you why it doesn't work, wtf do you want?

  if param.is_none() {
    // Handle, and continue, return an error etc
  }
  let value = param.as_ref().unwrap(); // or as_mut
  // Use `value` as normal.

Also, sometimes you just write software where you know the invariant is enforced so a type is never None, you can unwrap there too.

I find it interesting how a lot of people find Rust annoying because idiomatic Rust is a very strict language. You still get a ton of the benefits of Rust when writing non-idiomatic Rust. Just use the Rc<RefCell<>> and Arc<Mutex> and feel free to unwrap everything, nobody will punish you.

Hmm, I kind of disagree. The method literally returns “OK or an error”. It converts an Option into a Result and the name reflects that.

There is something of an inconsistency though, although IMHO it’s worth it. The `Result::ok()` method returns a Some if it’s Ok, and None otherwise, which is concise and intuitive but indeed different from `Option::ok_or`.

https://gist.github.com/tekacs/60b10000d314f9923d6b6a5af8c35...

where... in my code, I have:

  some_block({ ... }).infallible()

Then, there's an enum (at the bottom of the file) of different reasons that we believe that this should never fail, like:

  // e.g. we're in a service that writes to disk... and we can't write to disk
  some_operation.invariant(Reason::ExternalIssue)
  // we're not broken, the system wasn't set up correctly, e.g. a missing env var
  some_operation.invariant(Reason::DevOps)
  // this lock was poisoned... there's nothing useful that we can do _here_
  some_operation.invariant(Reason::Lock)
  // something in this function already checked this
  some_operation.invariant(Reason::ControlFlow)
  // u64 overflow of something that we increment once a second... which millennium are we in?
  some_operation.invariant(Reason::SuperRare)

This is all made available on both Result and Option.