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Comment by da39a3ee | Hacker News Reader

The article looks great and I’m looking forward to reading it; this comment is not a criticism of the article.

This API is the only bad thing about Rust!

  .expect("Could not read file")

It’s so unfortunate to have an API that reads

  .expect("thing we don’t expect")

I think we should all just forget it’s there and use

  .unwrap_or_else(|| panic!(“thing we don’t expect”))

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"expect" is like the word "assert". You express which invariant should always be true and therefore there should be no failure. The use of `.expect("Could not read file")` is actually wrong, because it can fail.

That is not how Rust documents expect() should be used. Rust's own documentation (https://doc.rust-lang.org/std/result/) contains:

  let mut file = File::create("valuable_data.txt").unwrap();
  file.write_all(b"important message").expect("failed to write message");

The use of .expect("Could not read file") is consistent with Rust's documentation.

And I agree with OP that .expect() is poorly named. I wouldn't raise it as an issue on the work of others who just use Rust and are stuck with it though.

I also wish I could write:

.or_panic(“unexpected fatal error”)

.unwrap_or_panic

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