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tcard opened this issue Oct 1, 2014 · 1 comment
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Rust Guide: incorrect explanation of Result.ok() / Option.expect() #17676

tcard opened this issue Oct 1, 2014 · 1 comment

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@tcard
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tcard commented Oct 1, 2014

Rust provides a method on these IoResults called ok(), which does the same thing as our match statement, but assuming that we have a valid value. If we don't, it will terminate our program. In this case, if we can't get input, our program doesn't work, so we're okay with that. In most cases, we would want to handle the error case explicitly. The result of ok() has a method, expect(), which allows us to give an error message if this crash happens.

If I'm not mistaken, ok() just turns the IoResult into an Option. It won't terminate the program. It's expect() which fails or unwraps the value.

Also, wouldn't a call to the IoResult's unwrap() be more direct? Although the custom failure message would be lost.
@huonw huonw added the A-docs label Oct 1, 2014
@steveklabnik
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I thought this was already fixed :/

lnicola pushed a commit to lnicola/rust that referenced this issue Jul 28, 2024
@bors
Auto merge of rust-lang#17676 - winstxnhdw:precise-capturing, r=Veykril
c0fd28b 
feat: add preliminary support for `+ use<..>` `precise_capturing` syntax

## Summary

This PR adds basic support for the following syntax.

```rs
fn captures<'a: 'a, 'b: 'b, T>() -> impl Sized + use<'b, T> {}
//                                  ~~~~~~~~~~~~~~~~~~~~~~~
//                          This opaque type does not capture `'a`.

fn outlives<'o, T: 'o>(_: T) {}

fn caller<'o, 'a, 'b: 'o, T: 'o>() {
    //        ~~
    //        ^ Note that we don't need `'a: 'o`.
    outlives::<'o>(captures::<'a, 'b, T>());
}
```

Related to rust-lang#17598
RalfJung pushed a commit to RalfJung/rust that referenced this issue Aug 1, 2024
@bors
Auto merge of rust-lang#17676 - winstxnhdw:precise-capturing, r=Veykril
3e1a4dc 
feat: add preliminary support for `+ use<..>` `precise_capturing` syntax

## Summary

This PR adds basic support for the following syntax.

```rs
fn captures<'a: 'a, 'b: 'b, T>() -> impl Sized + use<'b, T> {}
//                                  ~~~~~~~~~~~~~~~~~~~~~~~
//                          This opaque type does not capture `'a`.

fn outlives<'o, T: 'o>(_: T) {}

fn caller<'o, 'a, 'b: 'o, T: 'o>() {
    //        ~~
    //        ^ Note that we don't need `'a: 'o`.
    outlives::<'o>(captures::<'a, 'b, T>());
}
```

Related to rust-lang#17598
RalfJung pushed a commit to RalfJung/rust that referenced this issue Aug 1, 2024
@bors
Auto merge of rust-lang#17676 - winstxnhdw:precise-capturing, r=Veykril
7f314c6 
feat: add preliminary support for `+ use<..>` `precise_capturing` syntax

## Summary

This PR adds basic support for the following syntax.

```rs
fn captures<'a: 'a, 'b: 'b, T>() -> impl Sized + use<'b, T> {}
//                                  ~~~~~~~~~~~~~~~~~~~~~~~
//                          This opaque type does not capture `'a`.

fn outlives<'o, T: 'o>(_: T) {}

fn caller<'o, 'a, 'b: 'o, T: 'o>() {
    //        ~~
    //        ^ Note that we don't need `'a: 'o`.
    outlives::<'o>(captures::<'a, 'b, T>());
}
```

Related to rust-lang#17598
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@steveklabnik @tcard @huonw