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cast_ref_to_mut lint #3600

Merged
merged 6 commits into from
Jan 7, 2019
Merged

cast_ref_to_mut lint #3600

merged 6 commits into from
Jan 7, 2019

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KamilaBorowska
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@KamilaBorowska KamilaBorowska commented Dec 29, 2018 •
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I see this pattern way too often, and it's completely wrong. In fact, due to how common this incorrect pattern is, the Rustonomicon specifically points this out.

  • Transmuting an & to &mut is UB
    • Transmuting an & to &mut is always UB
    • No you can't do it
    • No you're not special

This is my first lint.

@KamilaBorowska KamilaBorowska force-pushed the cast-ref-to-mut branch 4 times, most recently from 15dc75f to cabac56 Compare December 29, 2018 22:42
@phansch phansch added the S-waiting-on-review Status: Awaiting review from the assignee but also interested parties label Dec 30, 2018
detrumi
detrumi reviewed Dec 30, 2018
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detrumi
detrumi reviewed Dec 30, 2018
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@KamilaBorowska
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Okay, added the new error message "casting &T to &mut T may cause undefined behaviour, consider instead using an UnsafeCell". This matches the error message when using the following in rustc:

fn main() {
    unsafe { std::mem::transmute::<&i32, &mut i32>(&3); }
}

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bors commented Jan 3, 2019

☔ The latest upstream changes (presumably #3603) made this pull request unmergeable. Please resolve the merge conflicts.

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bors commented Jan 5, 2019

☔ The latest upstream changes (presumably #3635) made this pull request unmergeable. Please resolve the merge conflicts.

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flip1995 commented Jan 7, 2019

I'd approve this. Only two questions left:

  • Do you think this lint should stay in the nursery group? Isn't it ready for the correctness group?
  • Can you squash these merge commits? (kind of also my fault, because it took me so long to review, sorry about that. Thanks for keeping this up with the master branch!)

@KamilaBorowska
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Sure.

@KamilaBorowska
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Isn't it ready for the correctness group?

It probably is, but I wanted to be safe.

@flip1995
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flip1995 commented Jan 7, 2019

@bors r+ Thanks!

@phansch
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phansch commented Jan 7, 2019

@bors retry (bors seems to have been down for a bit)

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phansch commented Jan 7, 2019 •
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@bors r=flip1995

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bors commented Jan 7, 2019

📌 Commit 27ea638 has been approved by flip1995

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bors commented Jan 7, 2019

💡 This pull request was already approved, no need to approve it again.

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bors commented Jan 7, 2019

📌 Commit 27ea638 has been approved by flip1995

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bors commented Jan 7, 2019

⌛ Testing commit 27ea638 with merge 140c165...

bors added a commit that referenced this pull request Jan 7, 2019
@bors
Auto merge of #3600 - xfix:cast-ref-to-mut, r=flip1995
140c165 
cast_ref_to_mut lint

I see this pattern way too often, and it's completely wrong. In fact, due to how common this incorrect pattern is, [the Rustonomicon specifically points this out](https://doc.rust-lang.org/nomicon/transmutes.html).

> - Transmuting an & to &mut is UB
>   - Transmuting an & to &mut is always UB
>   - No you can't do it
>   - No you're not special

This is my first lint.
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bors commented Jan 7, 2019

☀️ Test successful - status-appveyor, status-travis
Approved by: flip1995
Pushing 140c165 to master...

@bors bors merged commit 27ea638 into rust-lang:master Jan 7, 2019
This was referenced Jan 7, 2019
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@KamilaBorowska @bors @flip1995 @phansch @detrumi