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Merged
merged 1 commit into from
Jun 26, 2020
Merged

Provide suggestions for some moved value errors #73534

merged 1 commit into from
Jun 26, 2020

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estebank
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When encountering an used moved value where the previous move happened
in a match or if let pattern, suggest using ref. Fix #63988.

When encountering a &mut value that is used in multiple iterations of
a loop, suggest reborrowing it with &mut *. Fix #62112.

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r? @petrochenkov

(rust_highfive has picked a reviewer for you, use r? to override)

@rust-highfive rust-highfive added the S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. label Jun 20, 2020
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r? @matthewjasper (or someone else maintaining borrow checker)

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@bors r+

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bors commented Jun 21, 2020

📌 Commit 5faf657 has been approved by matthewjasper

@bors bors added S-waiting-on-bors Status: Waiting on bors to run and complete tests. Bors will change the label on completion. and removed S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. labels Jun 21, 2020
Manishearth added a commit to Manishearth/rust that referenced this pull request Jun 21, 2020
@Manishearth
Rollup merge of rust-lang#73534 - estebank:borrowck-suggestions, r=ma…
62ffd20 
…tthewjasper

Provide suggestions for some moved value errors

When encountering an used moved value where the previous move happened
in a `match` or `if let` pattern, suggest using `ref`. Fix rust-lang#63988.

When encountering a `&mut` value that is used in multiple iterations of
a loop, suggest reborrowing it with `&mut *`. Fix rust-lang#62112.
@Manishearth Manishearth mentioned this pull request Jun 21, 2020
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Manishearth added a commit to Manishearth/rust that referenced this pull request Jun 22, 2020
@Manishearth
Rollup merge of rust-lang#73534 - estebank:borrowck-suggestions, r=ma…
5e5d63d 
…tthewjasper

Provide suggestions for some moved value errors

When encountering an used moved value where the previous move happened
in a `match` or `if let` pattern, suggest using `ref`. Fix rust-lang#63988.

When encountering a `&mut` value that is used in multiple iterations of
a loop, suggest reborrowing it with `&mut *`. Fix rust-lang#62112.
@Manishearth Manishearth mentioned this pull request Jun 22, 2020
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@bors bors added S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. and removed S-waiting-on-bors Status: Waiting on bors to run and complete tests. Bors will change the label on completion. labels Jun 23, 2020
@estebank
Provide suggestions for some moved value errors
520461f 
When encountering an used moved value where the previous move happened
in a `match` or `if let` pattern, suggest using `ref`. Fix rust-lang#63988.

When encountering a `&mut` value that is used in multiple iterations of
a loop, suggest reborrowing it with `&mut *`. Fix rust-lang#62112.
@estebank estebank force-pushed the borrowck-suggestions branch from 5faf657 to 520461f Compare June 25, 2020 00:42
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@bors r=matthewjasper

rebased

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bors commented Jun 25, 2020

📌 Commit 520461f has been approved by matthewjasper

@bors bors added S-waiting-on-bors Status: Waiting on bors to run and complete tests. Bors will change the label on completion. and removed S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. labels Jun 25, 2020
Manishearth added a commit to Manishearth/rust that referenced this pull request Jun 26, 2020
@Manishearth
Rollup merge of rust-lang#73534 - estebank:borrowck-suggestions, r=ma…
0aef6ff 
…tthewjasper

Provide suggestions for some moved value errors

When encountering an used moved value where the previous move happened
in a `match` or `if let` pattern, suggest using `ref`. Fix rust-lang#63988.

When encountering a `&mut` value that is used in multiple iterations of
a loop, suggest reborrowing it with `&mut *`. Fix rust-lang#62112.
@Manishearth Manishearth mentioned this pull request Jun 26, 2020
Closed
Manishearth added a commit to Manishearth/rust that referenced this pull request Jun 26, 2020
@Manishearth
Rollup merge of rust-lang#73534 - estebank:borrowck-suggestions, r=ma…
050cb83 
…tthewjasper

Provide suggestions for some moved value errors

When encountering an used moved value where the previous move happened
in a `match` or `if let` pattern, suggest using `ref`. Fix rust-lang#63988.

When encountering a `&mut` value that is used in multiple iterations of
a loop, suggest reborrowing it with `&mut *`. Fix rust-lang#62112.
This was referenced Jun 26, 2020
Closed
Merged
bors added a commit to rust-lang-ci/rust that referenced this pull request Jun 26, 2020
@bors
Auto merge of rust-lang#73746 - Manishearth:rollup-80jnynm, r=Manishe…
e093b65 
…arth

Rollup of 14 pull requests

Successful merges:

 - rust-lang#72617 (Add a fast path for `std::thread::panicking`.)
 - rust-lang#72738 (Self contained linking option)
 - rust-lang#72770 (Implement mixed script confusable lint.)
 - rust-lang#73418 (Add unstable `core::mem::variant_count` intrinsic)
 - rust-lang#73460 (Emit line info for generator variants)
 - rust-lang#73534 (Provide suggestions for some moved value errors)
 - rust-lang#73538 (make commented examples use valid syntax, and be more consistent )
 - rust-lang#73581 (Create 0766 error code)
 - rust-lang#73619 (Document the mod keyword)
 - rust-lang#73621 (Document the mut keyword)
 - rust-lang#73648 (Document the return keyword)
 - rust-lang#73673 (Fix ptr doc warnings.)
 - rust-lang#73674 (Tweak binop errors)
 - rust-lang#73687 (Clean up E0701 explanation)

Failed merges:

 - rust-lang#73708 (Explain move errors that occur due to method calls involving `self` (take two))

r? @ghost
@bors bors merged commit 4a245ae into rust-lang:master Jun 26, 2020
@cuviper cuviper added this to the 1.46 milestone May 2, 2024
@ShE3py ShE3py mentioned this pull request Mar 13, 2025
Merged
matthiaskrgr added a commit to matthiaskrgr/rust that referenced this pull request Apr 3, 2025
@matthiaskrgr
Rollup merge of rust-lang#138462 - ShE3py:mut-borrow-in-loop, r=oli-obk
731ce84 
Dedup `&mut *` reborrow suggestion in loops

rust-lang#73534 added a reborrow suggestion in loops; rust-lang#127579 generalized this to generic parameters, making the suggestion triggers twice:
```rs
use std::io::Read;

fn decode_scalar(_reader: impl Read) {}
fn decode_array(reader: &mut impl Read) {
    for _ in 0.. {
        decode_scalar(reader);
    }
}
```
```
error[E0382]: use of moved value: `reader`
 --> src/lib.rs:6:23
  |
4 | fn decode_array(reader: &mut impl Read) {
  |                 ------ move occurs because `reader` has type `&mut impl Read`, which does not implement the `Copy` trait
5 |     for _ in 0.. {
  |     ------------ inside of this loop
6 |         decode_scalar(reader);
  |                       ^^^^^^ value moved here, in previous iteration of loop
  |
help: consider creating a fresh reborrow of `reader` here
  |
6 |         decode_scalar(&mut *reader);
  |                       ++++++
help: consider creating a fresh reborrow of `reader` here
  |
6 |         decode_scalar(&mut *reader);
  |                       ++++++
```
This PR removes the suggestion in loops, as it requires generic parameters anyway (i.e., the reborrow is automatic if there is no generic params).

`@rustbot` label +A-borrow-checker +A-diagnostics +A-suggestion-diagnostics +D-papercut
rust-timer added a commit to rust-lang-ci/rust that referenced this pull request Apr 4, 2025
@rust-timer
Unrolled build for rust-lang#138462
9808270 
Rollup merge of rust-lang#138462 - ShE3py:mut-borrow-in-loop, r=oli-obk

Dedup `&mut *` reborrow suggestion in loops

rust-lang#73534 added a reborrow suggestion in loops; rust-lang#127579 generalized this to generic parameters, making the suggestion triggers twice:
```rs
use std::io::Read;

fn decode_scalar(_reader: impl Read) {}
fn decode_array(reader: &mut impl Read) {
    for _ in 0.. {
        decode_scalar(reader);
    }
}
```
```
error[E0382]: use of moved value: `reader`
 --> src/lib.rs:6:23
  |
4 | fn decode_array(reader: &mut impl Read) {
  |                 ------ move occurs because `reader` has type `&mut impl Read`, which does not implement the `Copy` trait
5 |     for _ in 0.. {
  |     ------------ inside of this loop
6 |         decode_scalar(reader);
  |                       ^^^^^^ value moved here, in previous iteration of loop
  |
help: consider creating a fresh reborrow of `reader` here
  |
6 |         decode_scalar(&mut *reader);
  |                       ++++++
help: consider creating a fresh reborrow of `reader` here
  |
6 |         decode_scalar(&mut *reader);
  |                       ++++++
```
This PR removes the suggestion in loops, as it requires generic parameters anyway (i.e., the reborrow is automatic if there is no generic params).

`@rustbot` label +A-borrow-checker +A-diagnostics +A-suggestion-diagnostics +D-papercut
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