Add lint for & -> &mut transmutes #13146

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1. huonw

   added

   A-lint

   on Mar 26, 2014
2. nikomatsakis commented on Mar 26, 2014

   

   nikomatsakis

   on Mar 26, 2014

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   The proposed changes to intrinsics help here, because they wlil effectively forbid transmutes between types unless we can be sure of the size, which implies that one cannot transmute arbitrary types T to U and so on. We could even make these sorts of const casts illegal -- though somehow we have to make the Unsafe type able to do it. :)
3. nikomatsakis commented on Mar 26, 2014

   

   nikomatsakis

   on Mar 26, 2014

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   Oh, hmm, the RFC doesn't have the interesting parts. Nm.
4. emberian commented on Mar 28, 2014

   

   emberian

   on Mar 28, 2014

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   (I have this half-implemented in https://github.com/cmr/rust/tree/unsafe-transmutes)
5. nikomatsakis commented on Mar 28, 2014

   

   nikomatsakis

   on Mar 28, 2014

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   Ah, the proposed changes to transmute are in #12898, not the RFC.
6. steveklabnik commented on Apr 20, 2015

   

   steveklabnik

   on Apr 20, 2015

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   Triage: nothing has changed, these transmutes still silently work:

   use std::mem;
   
   fn main() {
       let x = 5;
   
       let y = &x;
   
       let z = unsafe { mem::transmute::<&i32, &mut i32>(y) };
   }
   
7. seanmonstar

   added a commit that references this issue on Apr 22, 2015

   lint: deny transmuting from immutable to mutable, since it's undefine…

   ...

   This issue will close once commit ae84d4f is merged into the 'master' branch.

   ae84d4f
8. seanmonstar

   added 3 commits that reference this issue on Apr 29, 2015

   lint: deny transmuting from immutable to mutable, since it's undefine…

   ...

   This issue will close once commit fadc86c is merged into the 'master' branch.

   fadc86c

   lint: deny transmuting from immutable to mutable, since it's undefine…

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   This issue will close once commit 6c30c6b is merged into the 'master' branch.

   6c30c6b

   lint: deny transmuting from immutable to mutable, since it's undefine…

   ...

   This issue will close once commit 2fdb714 is merged into the 'master' branch.

   2fdb714
9. seanmonstar

   added a commit that references this issue on May 5, 2015

   lint: deny transmuting from immutable to mutable, since it's undefine…

   ...

   This issue will close once commit 89fa21b is merged into the 'master' branch.

   89fa21b
10. seanmonstar

    added a commit that references this issue on May 6, 2015

    lint: deny transmuting from immutable to mutable, since it's undefine…

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    This issue will close once commit d131f33 is merged into the 'master' branch.

    d131f33
11. bors

    added a commit that references this issue on May 6, 2015

    Auto merge of #24392 - seanmonstar:lint-transmute-mut, r=alexcrichton

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    This issue will close once commit 8767e97 is merged into the 'main' branch.

    8767e97
12. bors

    closed this as completedin #24392on May 7, 2015
13. alexcrichton

    added a commit that references this issue on May 7, 2015

    lint: deny transmuting from immutable to mutable, since it's undefine…

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    This issue will close once commit 103d02f is merged into the 'incoming' branch.

    103d02f
14. flip1995

    added a commit that references this issue on Jul 25, 2024

    Auto merge of rust-lang#13146 - Alexendoo:cast-lossless-128, r=y21

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    5e6540f