This PR fixes a snippet of code on the error handling chapter of \"The Rust Programming Language\".
//cc @steveklabnik
The docs state that trying to compile the snippet will yield the following error:
```bash
anon>:13:5: 20:6 error: non-exhaustive patterns: `_` not covered [E0004]
```
But instead the error received is:
```bash
<anon>:22:46: 22:56 error: unresolved name `NewRelease`
<anon>:22 std::io::println(descriptive_probability(NewRelease));
^~~~~~~~~~
<anon>:22:5: 22:21 error: unresolved name `std::io::println`
<anon>:22 std::io::println(descriptive_probability(NewRelease));
^~~~~~~~~~~~~~~~
error: aborting due to 2 previous errors
playpen: application terminated with error code 101
```
After applying this PR the expected error is returned:
```bash
anon>:13:5: 20:6 error: non-exhaustive patterns: `_` not covered [E0004]
<anon>:13 match probability(&event) {
<anon>:14 1.00 => \"certain\",
<anon>:15 0.00 => \"impossible\",
<anon>:16 0.00 ... 0.25 => \"very unlikely\",
<anon>:17 0.25 ... 0.50 => \"unlikely\",
<anon>:18 0.50 ... 0.75 => \"likely\",
...
<anon>:13:5: 20:6 help: see the detailed explanation for E0004
error: aborting due to previous error
```
Grammatical update (and passive -> active, but I'm not sure if "Rust" is often used as a subject in the book; feel free to revert that part for style, but keep the subject-verb agreement)
I am not mentioning #[unsafe_drop_flag] because it should go away
eventually, and also because it's just an attribute, it's not
really a use of the `unsafe` keyword.
Fixes#26345
I am not mentioning #[unsafe_drop_flag] because it should go away
eventually, and also because it's just an attribute, it's not
really a use of the `unsafe` keyword.
Fixes#26345
In Chapter 5.9 (References and Borrowing), there is an example [at the very end](https://doc.rust-lang.org/stable/book/references-and-borrowing.html#use-after-free) which shows that declaring a reference before declaring the variable that it points to results in a compilation error. The book does not really mention why this happens though -- in the sections before, it has described how different scopes affects the lifetime of resources, but there is no mention of how resources within the same scope work.
This confused me a little, so I asked on #rust and got the answer that the resources are destroyed in the reverse order that they are declared, but the book makes no mention of it (as far as I can find) -- except in Chapter 5.21 (Drop), where it says:
> When `x` goes out of scope at the end of `main()`, the code for `Drop` will run. `Drop` has one method, which is also called `drop()`. It takes a mutable reference to `self`.
>
> That’s it! The mechanics of `Drop` are very simple, but there are some subtleties. For example, values are dropped in the opposite order they are declared. [...]
---
I feel like Chapter 5.9 (References and Borrowing) is probably the best place to put this information (as I have done in my additions), since it deals with other types of referencing and borrowing. However, since English is not my native language, the wording of my additions perhaps are a little "off" -- any feedback on them is appreciated.
In particular, I found that the disclaimer (promised in the second paragraph) doesn't stand out right now. I think the extra headers help with scanning this document, and making it easier to discern which steps are relevant to my particular flow through the options.
In particular, I found that the disclaimer (promised in the second paragraph) doesn't stand out right now. I think the extra headers help with scanning this document, and making it easier to discern which steps are relevant to my particular flow through the options.
I'm currently reading the rust book and this variable name tripped me up.
Because it was called "input", I thought at first it might contain the line
read by read_line(). This new variable name will be more instructive to rust
beginners.
