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rename y to _y to get the correct compile error #1769

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merged 3 commits into from
Nov 18, 2023

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Without this change, the error is:

   Compiling playground v0.0.1 (/playground)
warning: unused variable: `y`
  --> src/main.rs:13:9
   |
13 |     let y: &'a i32 = &_x;
   |         ^ help: if this is intentional, prefix it with an underscore: `_y`
   |
   = note: `#[warn(unused_variables)]` on by default

error[E0597]: `_x` does not live long enough
  --> src/main.rs:13:22
   |
9  | fn failed_borrow<'a>() {
   |                  -- lifetime `'a` defined here
10 |     let _x = 12;
   |         -- binding `_x` declared here
...
13 |     let y: &'a i32 = &_x;
   |            -------   ^^^ borrowed value does not live long enough
   |            |
   |            type annotation requires that `_x` is borrowed for `'a`
...
17 | }
   | - `_x` dropped here while still borrowed

For more information about this error, try `rustc --explain E0597`.
warning: `playground` (bin "playground") generated 1 warning
error: could not compile `playground` (bin "playground") due to previous error; 1 warning emitted

Without this change, the error is:
```
   Compiling playground v0.0.1 (/playground)
warning: unused variable: `y`
  --> src/main.rs:13:9
   |
13 |     let y: &'a i32 = &_x;
   |         ^ help: if this is intentional, prefix it with an underscore: `_y`
   |
   = note: `#[warn(unused_variables)]` on by default

error[E0597]: `_x` does not live long enough
  --> src/main.rs:13:22
   |
9  | fn failed_borrow<'a>() {
   |                  -- lifetime `'a` defined here
10 |     let _x = 12;
   |         -- binding `_x` declared here
...
13 |     let y: &'a i32 = &_x;
   |            -------   ^^^ borrowed value does not live long enough
   |            |
   |            type annotation requires that `_x` is borrowed for `'a`
...
17 | }
   | - `_x` dropped here while still borrowed

For more information about this error, try `rustc --explain E0597`.
warning: `playground` (bin "playground") generated 1 warning
error: could not compile `playground` (bin "playground") due to previous error; 1 warning emitted
```
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rustbot commented Nov 9, 2023

Thanks for the pull request, and welcome! The Rust team is excited to review your changes, and you should hear from @marioidival (or someone else) soon.

@kberov
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kberov commented Nov 9, 2023

True. Although the message for the y variable is only a warning, the learner may get confused.

@@ -40,7 +40,7 @@ fn failed_borrow<'a>() {
let _x = 12;

// ERROR: `_x` does not live long enough
let y: &'a i32 = &_x;
let _y: &'a i32 = &_x;
// Attempting to use the lifetime `'a` as an explicit type annotation
// inside the function will fail because the lifetime of `&_x` is shorter
// than that of `y`. A short lifetime cannot be coerced into a longer one.
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Can you change that reference?

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see update in 3dffa1e

If that is what you meant, let me know and I'll squash the commits to keep git history tidy.

@marioidival marioidival merged commit a658124 into rust-lang:master Nov 18, 2023
1 check passed
compiler-errors added a commit to compiler-errors/rust that referenced this pull request Nov 21, 2023
Update books

## rust-lang/book

2 commits in 5b6c1ceaa62ecbd6caef08df39b33b3938e99deb..71352deb20727b4dda9ebfe8182709d5bf17dfea
2023-11-09 14:49:45 UTC to 2023-11-09 14:49:16 UTC

- Fixed 'Devtools' link (rust-lang/book#3770)
- Fix mdBook links (rust-lang/book#3769)

## rust-lang/rust-by-example

7 commits in 311b84962016b28c75525c86e7b3f49fd9101a39..a6581246f96837113968c02187db24f742af3908
2023-11-18 21:45:20 UTC to 2023-11-07 22:32:53 UTC

- rename `y` to `_y` to get the correct compile error (rust-lang/rust-by-example#1769)
- fix test name in cargo/test.md (rust-lang/rust-by-example#1768)
- Various minor edits for typo fixes, formatting fixes, and clarifications (rust-lang/rust-by-example#1765)
- Update closures.md to correct a typo (rust-lang/rust-by-example#1763)
- Link to the Bulgarian translation (rust-lang/rust-by-example#1764)
- Fix asm example explanation for `inlateout` usage (22.1 Inline Assembly) (rust-lang/rust-by-example#1766)
- Update index.md: Added descriptions for the 'leftover' points (rust-lang/rust-by-example#1767)

## rust-lang/rustc-dev-guide

3 commits in 77dbe5782b2488af3bb489ad702eaff438f465bf..ddb8b1309f9e905804cea1e248a4572fed6b464b
2023-11-18 21:08:13 UTC to 2023-11-08 14:43:50 UTC

- Add link for unsize.md (rust-lang/rustc-dev-guide#1825)
- Fix typo in contribution walkthrough (rust-lang/rustc-dev-guide#1824)
- Update documentation for coverage tests (rust-lang/rustc-dev-guide#1823)
Noratrieb added a commit to Noratrieb/rust that referenced this pull request Nov 21, 2023
Update books

## rust-lang/book

2 commits in 5b6c1ceaa62ecbd6caef08df39b33b3938e99deb..71352deb20727b4dda9ebfe8182709d5bf17dfea
2023-11-09 14:49:45 UTC to 2023-11-09 14:49:16 UTC

- Fixed 'Devtools' link (rust-lang/book#3770)
- Fix mdBook links (rust-lang/book#3769)

## rust-lang/rust-by-example

7 commits in 311b84962016b28c75525c86e7b3f49fd9101a39..a6581246f96837113968c02187db24f742af3908
2023-11-18 21:45:20 UTC to 2023-11-07 22:32:53 UTC

- rename `y` to `_y` to get the correct compile error (rust-lang/rust-by-example#1769)
- fix test name in cargo/test.md (rust-lang/rust-by-example#1768)
- Various minor edits for typo fixes, formatting fixes, and clarifications (rust-lang/rust-by-example#1765)
- Update closures.md to correct a typo (rust-lang/rust-by-example#1763)
- Link to the Bulgarian translation (rust-lang/rust-by-example#1764)
- Fix asm example explanation for `inlateout` usage (22.1 Inline Assembly) (rust-lang/rust-by-example#1766)
- Update index.md: Added descriptions for the 'leftover' points (rust-lang/rust-by-example#1767)

## rust-lang/rustc-dev-guide

3 commits in 77dbe5782b2488af3bb489ad702eaff438f465bf..ddb8b1309f9e905804cea1e248a4572fed6b464b
2023-11-18 21:08:13 UTC to 2023-11-08 14:43:50 UTC

- Add link for unsize.md (rust-lang/rustc-dev-guide#1825)
- Fix typo in contribution walkthrough (rust-lang/rustc-dev-guide#1824)
- Update documentation for coverage tests (rust-lang/rustc-dev-guide#1823)
rust-timer added a commit to rust-lang-ci/rust that referenced this pull request Nov 21, 2023
Rollup merge of rust-lang#118097 - rustbot:docs-update, r=ehuss

Update books

## rust-lang/book

2 commits in 5b6c1ceaa62ecbd6caef08df39b33b3938e99deb..71352deb20727b4dda9ebfe8182709d5bf17dfea
2023-11-09 14:49:45 UTC to 2023-11-09 14:49:16 UTC

- Fixed 'Devtools' link (rust-lang/book#3770)
- Fix mdBook links (rust-lang/book#3769)

## rust-lang/rust-by-example

7 commits in 311b84962016b28c75525c86e7b3f49fd9101a39..a6581246f96837113968c02187db24f742af3908
2023-11-18 21:45:20 UTC to 2023-11-07 22:32:53 UTC

- rename `y` to `_y` to get the correct compile error (rust-lang/rust-by-example#1769)
- fix test name in cargo/test.md (rust-lang/rust-by-example#1768)
- Various minor edits for typo fixes, formatting fixes, and clarifications (rust-lang/rust-by-example#1765)
- Update closures.md to correct a typo (rust-lang/rust-by-example#1763)
- Link to the Bulgarian translation (rust-lang/rust-by-example#1764)
- Fix asm example explanation for `inlateout` usage (22.1 Inline Assembly) (rust-lang/rust-by-example#1766)
- Update index.md: Added descriptions for the 'leftover' points (rust-lang/rust-by-example#1767)

## rust-lang/rustc-dev-guide

3 commits in 77dbe5782b2488af3bb489ad702eaff438f465bf..ddb8b1309f9e905804cea1e248a4572fed6b464b
2023-11-18 21:08:13 UTC to 2023-11-08 14:43:50 UTC

- Add link for unsize.md (rust-lang/rustc-dev-guide#1825)
- Fix typo in contribution walkthrough (rust-lang/rustc-dev-guide#1824)
- Update documentation for coverage tests (rust-lang/rustc-dev-guide#1823)
@aviad-dev aviad-dev deleted the patch-2 branch January 24, 2024 07:52
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4 participants