forbid mutable references in all constant contexts except for const-fns #72934

pvdrz · 2020-06-03T00:23:54Z

PR to address #71212

rust-highfive · 2020-06-03T00:23:57Z

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

ecstatic-morse · 2020-06-03T03:51:09Z

My question is how this works, which will need more than a single line 😄. HasMutInterior is meant specifically for immutable borrows of Cells, so modifying it in this way is suspicious to me. What error messages are emitted for the examples in #71212, specifically the ones with raw pointers?

ecstatic-morse · 2020-06-03T03:51:23Z

r? @ecstatic-morse

pvdrz · 2020-06-07T00:27:43Z

@ecstatic-morse I reutilized MutBorrow for this because it is only triggered on rvalues.

rust-highfive · 2020-06-07T01:22:37Z

The job x86_64-gnu-llvm-8 of your PR failed (pretty log, raw log). Through arcane magic we have determined that the following fragments from the build log may contain information about the problem.

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##[section]Starting: Linux x86_64-gnu-llvm-8
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##[section]Starting: Checkout rust-lang/rust@refs/pull/72934/merge to s
Task         : Get sources
Description  : Get sources from a repository. Supports Git, TfsVC, and SVN repositories.
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Author       : Microsoft
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---
---- [ui] ui/consts/const-mut-refs/const_mut_address_of.rs stdout ----

error: test compilation failed although it shouldn't!
status: exit code: 1
command: "/checkout/obj/build/x86_64-unknown-linux-gnu/stage2/bin/rustc" "/checkout/src/test/ui/consts/const-mut-refs/const_mut_address_of.rs" "-Zthreads=1" "--target=x86_64-unknown-linux-gnu" "--error-format" "json" "-Zui-testing" "-Zdeduplicate-diagnostics=no" "--emit" "metadata" "-C" "prefer-dynamic" "--out-dir" "/checkout/obj/build/x86_64-unknown-linux-gnu/test/ui/consts/const-mut-refs/const_mut_address_of" "-A" "unused" "-Crpath" "-O" "-Cdebuginfo=0" "-Zunstable-options" "-Lnative=/checkout/obj/build/x86_64-unknown-linux-gnu/native/rust-test-helpers" "-L" "/checkout/obj/build/x86_64-unknown-linux-gnu/test/ui/consts/const-mut-refs/const_mut_address_of/auxiliary"
------------------------------------------

------------------------------------------
stderr:
stderr:
------------------------------------------
error[E0658]: references in constants may only refer to immutable values
  --> /checkout/src/test/ui/consts/const-mut-refs/const_mut_address_of.rs:26:5
   |
LL |     foo().bar();
   |     ^^^^^ constants require immutable values
   |
   = note: see issue #57349 <***/issues/57349> for more information
   = help: add `#![feature(const_mut_refs)]` to the crate attributes to enable
error[E0658]: references in constants may only refer to immutable values
  --> /checkout/src/test/ui/consts/const-mut-refs/const_mut_address_of.rs:27:9
   |
LL |     baz(&mut foo());
LL |     baz(&mut foo());
   |         ^^^^^^^^^^ constants require immutable values
   |
   = note: see issue #57349 <***/issues/57349> for more information
   = help: add `#![feature(const_mut_refs)]` to the crate attributes to enable
error: aborting due to 2 previous errors

For more information about this error, try `rustc --explain E0658`.


------------------------------------------


---- [ui] ui/consts/const-mut-refs/const_mut_refs.rs stdout ----

error: test compilation failed although it shouldn't!
status: exit code: 1
command: "/checkout/obj/build/x86_64-unknown-linux-gnu/stage2/bin/rustc" "/checkout/src/test/ui/consts/const-mut-refs/const_mut_refs.rs" "-Zthreads=1" "--target=x86_64-unknown-linux-gnu" "--error-format" "json" "-Zui-testing" "-Zdeduplicate-diagnostics=no" "-C" "prefer-dynamic" "-o" "/checkout/obj/build/x86_64-unknown-linux-gnu/test/ui/consts/const-mut-refs/const_mut_refs/a" "-Crpath" "-O" "-Cdebuginfo=0" "-Zunstable-options" "-Lnative=/checkout/obj/build/x86_64-unknown-linux-gnu/native/rust-test-helpers" "-L" "/checkout/obj/build/x86_64-unknown-linux-gnu/test/ui/consts/const-mut-refs/const_mut_refs/auxiliary"
------------------------------------------

------------------------------------------
stderr:
stderr:
------------------------------------------
error[E0658]: references in constants may only refer to immutable values
  --> /checkout/src/test/ui/consts/const-mut-refs/const_mut_refs.rs:33:17
   |
LL |     let _: [(); foo().bar()] = [(); 1];
   |                 ^^^^^ constants require immutable values
   |
   = note: see issue #57349 <***/issues/57349> for more information
   = help: add `#![feature(const_mut_refs)]` to the crate attributes to enable
error[E0658]: references in constants may only refer to immutable values
  --> /checkout/src/test/ui/consts/const-mut-refs/const_mut_refs.rs:34:21
   |
   |
LL |     let _: [(); baz(&mut foo())] = [(); 2];
   |                     ^^^^^^^^^^ constants require immutable values
   |
   = note: see issue #57349 <***/issues/57349> for more information
   = help: add `#![feature(const_mut_refs)]` to the crate attributes to enable
error[E0658]: references in constants may only refer to immutable values
  --> /checkout/src/test/ui/consts/const-mut-refs/const_mut_refs.rs:35:22
   |
   |
LL |     let _: [(); bazz(&mut foo())] = [(); 3];
   |                      ^^^^^^^^^^ constants require immutable values
   |
   = note: see issue #57349 <***/issues/57349> for more information
   = help: add `#![feature(const_mut_refs)]` to the crate attributes to enable
error: aborting due to 3 previous errors

For more information about this error, try `rustc --explain E0658`.

---

+ error[E0658]: references in constants may only refer to immutable values
+   --> $DIR/projection_qualif.rs:10:27
+    |
+ LL |         let b: *mut u32 = &mut a;
+    |                           ^^^^^^ constants require immutable values
+    |
+    = note: see issue #57349 <***/issues/57349> for more information
+    = help: add `#![feature(const_mut_refs)]` to the crate attributes to enable
1 error[E0658]: dereferencing raw pointers in constants is unstable
2   --> $DIR/projection_qualif.rs:11:18
3    |


7    = note: see issue #51911 <***/issues/51911> for more information
9 
- error: aborting due to previous error
+ error: aborting due to 2 previous errors
11 
11 
12 For more information about this error, try `rustc --explain E0658`.
13 


The actual stderr differed from the expected stderr.
Actual stderr saved to /checkout/obj/build/x86_64-unknown-linux-gnu/test/ui/consts/projection_qualif.mut_refs/projection_qualif.mut_refs.stderr
To update references, rerun the tests and pass the `--bless` flag
To only update this specific test, also pass `--test-args consts/projection_qualif.rs`

error in revision `mut_refs`: 1 errors occurred comparing output.
status: exit code: 1
command: "/checkout/obj/build/x86_64-unknown-linux-gnu/stage2/bin/rustc" "/checkout/src/test/ui/consts/projection_qualif.rs" "-Zthreads=1" "--target=x86_64-unknown-linux-gnu" "--cfg" "mut_refs" "--error-format" "json" "-Zui-testing" "-Zdeduplicate-diagnostics=no" "--emit" "metadata" "-C" "prefer-dynamic" "--out-dir" "/checkout/obj/build/x86_64-unknown-linux-gnu/test/ui/consts/projection_qualif.mut_refs" "-A" "unused" "-Crpath" "-O" "-Cdebuginfo=0" "-Zunstable-options" "-Lnative=/checkout/obj/build/x86_64-unknown-linux-gnu/native/rust-test-helpers" "-L" "/checkout/obj/build/x86_64-unknown-linux-gnu/test/ui/consts/projection_qualif.mut_refs/auxiliary"
------------------------------------------

------------------------------------------
stderr:
stderr:
------------------------------------------
error[E0658]: references in constants may only refer to immutable values
  --> /checkout/src/test/ui/consts/projection_qualif.rs:10:27
   |
LL |         let b: *mut u32 = &mut a; //[stock]~ ERROR may only refer to immutable values
   |                           ^^^^^^ constants require immutable values
   |
   = note: see issue #57349 <***/issues/57349> for more information
   = help: add `#![feature(const_mut_refs)]` to the crate attributes to enable
error[E0658]: dereferencing raw pointers in constants is unstable
  --> /checkout/src/test/ui/consts/projection_qualif.rs:11:18
   |
   |
LL |         unsafe { *b = 5; } //~ ERROR dereferencing raw pointers in constants
   |
   |
   = note: see issue #51911 <***/issues/51911> for more information

error: aborting due to 2 previous errors

For more information about this error, try `rustc --explain E0658`.
---
---- [ui] ui/consts/read_from_static_mut_ref.rs stdout ----

error: test compilation failed although it shouldn't!
status: exit code: 1
command: "/checkout/obj/build/x86_64-unknown-linux-gnu/stage2/bin/rustc" "/checkout/src/test/ui/consts/read_from_static_mut_ref.rs" "-Zthreads=1" "--target=x86_64-unknown-linux-gnu" "--error-format" "json" "-Zui-testing" "-Zdeduplicate-diagnostics=no" "-C" "prefer-dynamic" "-o" "/checkout/obj/build/x86_64-unknown-linux-gnu/test/ui/consts/read_from_static_mut_ref/a" "-Crpath" "-O" "-Cdebuginfo=0" "-Zunstable-options" "-Lnative=/checkout/obj/build/x86_64-unknown-linux-gnu/native/rust-test-helpers" "-L" "/checkout/obj/build/x86_64-unknown-linux-gnu/test/ui/consts/read_from_static_mut_ref/auxiliary"
------------------------------------------

------------------------------------------
stderr:
stderr:
------------------------------------------
error[E0658]: references in statics may only refer to immutable values
  --> /checkout/src/test/ui/consts/read_from_static_mut_ref.rs:5:27
   |
LL | static OH_YES: &mut i32 = &mut 42;
   |                           ^^^^^^^ statics require immutable values
   |
   = note: see issue #57349 <***/issues/57349> for more information
   = help: add `#![feature(const_mut_refs)]` to the crate attributes to enable
error: aborting due to previous error

For more information about this error, try `rustc --explain E0658`.

---
-   --> $DIR/static_mut_containing_mut_ref2.rs:7:45
+ error[E0658]: references in statics may only refer to immutable values
+   --> $DIR/static_mut_containing_mut_ref2.rs:7:46
3    |
4 LL | pub static mut STDERR_BUFFER: () = unsafe { *(&mut STDERR_BUFFER_SPACE) = 42; };
-    |                                             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ modifying a static's initial value from another static's initializer
+    |                                              ^^^^^^^^^^^^^^^^^^^^^^^^^^ statics require immutable values
+    |
+    = note: see issue #57349 <***/issues/57349> for more information
+    = help: add `#![feature(const_mut_refs)]` to the crate attributes to enable
7 error: aborting due to previous error
8 

- For more information about this error, try `rustc --explain E0080`.
- For more information about this error, try `rustc --explain E0080`.
+ For more information about this error, try `rustc --explain E0658`.
10 


The actual stderr differed from the expected stderr.
Actual stderr saved to /checkout/obj/build/x86_64-unknown-linux-gnu/test/ui/consts/static_mut_containing_mut_ref2.mut_refs/static_mut_containing_mut_ref2.mut_refs.stderr
To update references, rerun the tests and pass the `--bless` flag
To only update this specific test, also pass `--test-args consts/static_mut_containing_mut_ref2.rs`

error in revision `mut_refs`: 1 errors occurred comparing output.
status: exit code: 1
command: "/checkout/obj/build/x86_64-unknown-linux-gnu/stage2/bin/rustc" "/checkout/src/test/ui/consts/static_mut_containing_mut_ref2.rs" "-Zthreads=1" "--target=x86_64-unknown-linux-gnu" "--cfg" "mut_refs" "--error-format" "json" "-Zui-testing" "-Zdeduplicate-diagnostics=no" "--emit" "metadata" "-C" "prefer-dynamic" "--out-dir" "/checkout/obj/build/x86_64-unknown-linux-gnu/test/ui/consts/static_mut_containing_mut_ref2.mut_refs" "-A" "unused" "-Crpath" "-O" "-Cdebuginfo=0" "-Zunstable-options" "-Lnative=/checkout/obj/build/x86_64-unknown-linux-gnu/native/rust-test-helpers" "-L" "/checkout/obj/build/x86_64-unknown-linux-gnu/test/ui/consts/static_mut_containing_mut_ref2.mut_refs/auxiliary"
------------------------------------------

------------------------------------------
stderr:
stderr:
------------------------------------------
error[E0658]: references in statics may only refer to immutable values
  --> /checkout/src/test/ui/consts/static_mut_containing_mut_ref2.rs:7:46
   |
LL | pub static mut STDERR_BUFFER: () = unsafe { *(&mut STDERR_BUFFER_SPACE) = 42; };
   |                                              ^^^^^^^^^^^^^^^^^^^^^^^^^^ statics require immutable values
   |
   = note: see issue #57349 <***/issues/57349> for more information
   = help: add `#![feature(const_mut_refs)]` to the crate attributes to enable
error: aborting due to previous error

For more information about this error, try `rustc --explain E0658`.

---
thread 'main' panicked at 'Some tests failed', src/tools/compiletest/src/main.rs:348:22
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace


command did not execute successfully: "/checkout/obj/build/x86_64-unknown-linux-gnu/stage0-tools-bin/compiletest" "--compile-lib-path" "/checkout/obj/build/x86_64-unknown-linux-gnu/stage2/lib" "--run-lib-path" "/checkout/obj/build/x86_64-unknown-linux-gnu/stage2/lib/rustlib/x86_64-unknown-linux-gnu/lib" "--rustc-path" "/checkout/obj/build/x86_64-unknown-linux-gnu/stage2/bin/rustc" "--src-base" "/checkout/src/test/ui" "--build-base" "/checkout/obj/build/x86_64-unknown-linux-gnu/test/ui" "--stage-id" "stage2-x86_64-unknown-linux-gnu" "--mode" "ui" "--target" "x86_64-unknown-linux-gnu" "--host" "x86_64-unknown-linux-gnu" "--llvm-filecheck" "/usr/lib/llvm-8/bin/FileCheck" "--nodejs" "/usr/bin/node" "--host-rustcflags" "-Crpath -O -Cdebuginfo=0 -Zunstable-options  -Lnative=/checkout/obj/build/x86_64-unknown-linux-gnu/native/rust-test-helpers" "--target-rustcflags" "-Crpath -O -Cdebuginfo=0 -Zunstable-options  -Lnative=/checkout/obj/build/x86_64-unknown-linux-gnu/native/rust-test-helpers" "--docck-python" "/usr/bin/python2.7" "--lldb-python" "/usr/bin/python2.7" "--gdb" "/usr/bin/gdb" "--quiet" "--llvm-version" "8.0.0" "--system-llvm" "--cc" "" "--cxx" "" "--cflags" "" "--llvm-components" "" "--adb-path" "adb" "--adb-test-dir" "/data/tmp/work" "--android-cross-path" "" "--color" "always"


failed to run: /checkout/obj/build/bootstrap/debug/bootstrap test --exclude src/tools/tidy
Build completed unsuccessfully in 0:52:07
Build completed unsuccessfully in 0:52:07
== clock drift check ==
  local time: Sun Jun  7 01:22:31 UTC 2020
  network time: Sun, 07 Jun 2020 01:22:31 GMT
== end clock drift check ==

##[error]Bash exited with code '1'.
##[section]Finishing: Run build
##[section]Starting: Checkout rust-lang/rust@refs/pull/72934/merge to s
Task         : Get sources
Description  : Get sources from a repository. Supports Git, TfsVC, and SVN repositories.
Version      : 1.0.0
Author       : Microsoft
Author       : Microsoft
Help         : [More Information](https://go.microsoft.com/fwlink/?LinkId=798199)
==============================================================================
Cleaning any cached credential from repository: rust-lang/rust (GitHub)
##[section]Finishing: Checkout rust-lang/rust@refs/pull/72934/merge to s
Cleaning up task key
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Terminate orphan process: pid (3815) (python)
##[section]Finishing: Finalize Job

I'm a bot! I can only do what humans tell me to, so if this was not helpful or you have suggestions for improvements, please ping or otherwise contact @rust-lang/infra. (Feature Requests)

ecstatic-morse

I think we need to improve diagnostics a bit.

src/test/ui/consts/const-mut-refs/const_mut_address_of.stderr

src/test/ui/consts/const-mut-refs/const_mut_refs.stderr

src/test/ui/consts/read_from_static_mut_ref.rs

src/librustc_mir/transform/check_consts/ops.rs

ecstatic-morse · 2020-06-18T16:05:01Z

Error messages look good to me now. Can you add an error code and description for this like oli mentioned? After that I think this is ready.

pvdrz · 2020-06-18T22:58:47Z

@ecstatic-morse @oli-obk I think we are ready then.

src/librustc_error_codes/error_codes/E0763.md

oli-obk · 2020-06-19T08:58:18Z

r=me with the documentation suggestion or something similarly expanatory.

@bors delegate+

bors · 2020-06-19T08:58:20Z

✌️ @christianpoveda can now approve this pull request

pvdrz · 2020-06-19T15:39:51Z

@bors r+

bors · 2020-06-19T15:39:52Z

📌 Commit 5302bd755d5a2a150083fc616e24361ee45d887b has been approved by christianpoveda

oli-obk · 2020-06-19T15:41:28Z

you need to write bors r=oli-obk in order for the review to be able to be blamed on me ;) r+ is just shorthand for r=yourself

@bors r+

bors · 2020-06-19T15:41:29Z

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

There's another pull request that is currently being tested, blocking this pull request: Self contained linking option #72738

bors · 2020-06-19T15:41:30Z

📌 Commit 5302bd755d5a2a150083fc616e24361ee45d887b has been approved by oli-obk

pvdrz · 2020-06-19T15:43:22Z

heh, thanks I've never used bors before :P

bors · 2020-06-19T16:11:00Z

☔ The latest upstream changes (presumably #73504) made this pull request unmergeable. Please resolve the merge conflicts.

oli-obk · 2020-06-19T17:59:19Z

@bors r+

bors · 2020-06-19T17:59:20Z

📌 Commit 6eb7a2dc0f0df32c2ef380d8a06086db5bdcfc20 has been approved by oli-obk

pvdrz · 2020-06-20T00:20:33Z

@bors r=oli-obk

bors · 2020-06-20T00:20:34Z

📌 Commit 96031e2 has been approved by oli-obk

@ghost

…arth Rollup of 16 pull requests Successful merges: - rust-lang#71420 (Specialization is unsound) - rust-lang#71899 (Refactor `try_find` a little) - rust-lang#72689 (add str to common types) - rust-lang#72791 (update coerce docs and unify relevant tests) - rust-lang#72934 (forbid mutable references in all constant contexts except for const-fns) - rust-lang#73027 (Make `need_type_info_err` more conservative) - rust-lang#73347 (Diagnose use of incompatible sanitizers) - rust-lang#73359 (shim.rs: avoid creating `Call` terminators calling `Self`) - rust-lang#73399 (Clean up E0668 explanation) - rust-lang#73436 (Clean up E0670 explanation) - rust-lang#73440 (Add src/librustdoc as an alias for src/tools/rustdoc) - rust-lang#73442 (pretty/mir: const value enums with no variants) - rust-lang#73452 (Unify region variables when projecting associated types) - rust-lang#73458 (Use alloc::Layout in DroplessArena API) - rust-lang#73484 (Update the doc for std::prelude to the correct behavior) - rust-lang#73506 (Bump Rustfmt and RLS) Failed merges: r? @ghost

This commit includes work-arounds for the following changes in the compiler: - Raw pointers as const generic parameters are now forbidden. <rust-lang/rust#73398> This means the work-around for ICE caused by `&'static [_]` const generic parameters doesn't work anymore. An alternative work-around is yet to be implemented. - Mutable references are now forbidden in all constant contexts except for `const fn`s. <rust-lang/rust#72934> Working around this change was as easy as mechanically replacing `const` with `const fn` for most cases. The only tricky case was the definition of `id_map` inside `build!`, which is a macro meant to be called inside a `const` item. The type of `id_map` isn't explicitly specified but is rather implied by a given configuration function, so this couldn't be mechanically replaced with a `const` item. To resolve this problem, I added an explicit type to `build!`'s signature.

rust-highfive assigned matthewjasper Jun 3, 2020

rust-highfive added the S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. label Jun 3, 2020

rust-highfive assigned ecstatic-morse and unassigned matthewjasper Jun 3, 2020

pvdrz changed the title ~~include mutable borrows in HasMutInterior~~ forbid mutable references in all constant contexts except for const-fns Jun 7, 2020

pvdrz marked this pull request as ready for review June 9, 2020 01:45

ecstatic-morse reviewed Jun 11, 2020

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pvdrz requested a review from ecstatic-morse June 15, 2020 17:01

oli-obk reviewed Jun 18, 2020

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src/librustc_mir/transform/check_consts/ops.rs Outdated Show resolved Hide resolved

oli-obk reviewed Jun 19, 2020

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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 19, 2020

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 19, 2020

pvdrz added 3 commits June 19, 2020 11:48

forbid mutable references in all constants except const fns

2f9d338

update tests

014e605

update diagnostics for &mut in constants

1f48465

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 19, 2020

add new error code

96031e2

Manishearth mentioned this pull request Jun 20, 2020

Rollup of 16 pull requests #73528

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bors merged commit dac512e into rust-lang:master Jun 20, 2020

pvdrz deleted the mut-borrows-in-consts branch June 20, 2020 14:12

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forbid mutable references in all constant contexts except for const-fns #72934

forbid mutable references in all constant contexts except for const-fns #72934

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forbid mutable references in all constant contexts except for const-fns #72934

forbid mutable references in all constant contexts except for const-fns #72934

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