experiment: remove value-based reasoning for interior mutability #122789

RalfJung · 2024-03-20T19:10:54Z

This also stabilizes const_refs_to_cell as it's just a crater experiment anyway and that reduces the amount of regressions.

rustbot · 2024-03-20T19:11:02Z

r? @wesleywiser

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rustbot · 2024-03-20T19:11:04Z

Some changes occurred in exhaustiveness checking

cc @Nadrieril

Some changes occurred to MIR optimizations

cc @rust-lang/wg-mir-opt

RalfJung · 2024-03-20T19:13:17Z

Sorry for the pings, I forgot to mark this a draft. (Why does github make that so annoying? Just give me a checkbox, instead of remember this decision for the next PR...)

RalfJung · 2024-03-20T19:13:49Z

@bors try

…<try> experiment: remove value-based reasoning for interior mutability This also stabilizes `const_refs_to_cell` as it's just a crater experiment anyway and that reduces the amount of regressions.

bors · 2024-03-20T19:15:00Z

⌛ Trying commit 3660dd9 with merge cb4bf0e...

Nadrieril · 2024-03-20T19:17:29Z

compiler/rustc_pattern_analysis/src/lib.rs

@@ -2,6 +2,7 @@

 #![allow(rustc::untranslatable_diagnostic)]
 #![allow(rustc::diagnostic_outside_of_impl)]
+#![feature(freeze)]


If this actually gets merged, please set this only when feature = "rustc". This crate needs to build on stable for rust-analyzer.

is it needed just for this?

rust/compiler/rustc_pattern_analysis/src/pat.rs

Line 250 in 94b72d6

PatOrWild::Wild => &Wildcard,

This is an experiment, it won't get merged. Also the crate can't build on stable any more with this rustc change.

is it needed just for this?

Yes. That previously got promoted even though other enum variants have interior mutability, which is not entirely a sound thing to do (Cc rust-lang/unsafe-code-guidelines#493).

rust-log-analyzer · 2024-03-20T19:29:57Z

The job x86_64-gnu-llvm-17 failed! Check out the build log: (web) (plain)

Click to see the possible cause of the failure (guessed by this bot)

#17 exporting to docker image format
#17 sending tarball 45.8s done
#17 DONE 50.6s
##[endgroup]
Setting extra environment values for docker:  --env ENABLE_GCC_CODEGEN=1 --env GCC_EXEC_PREFIX=/usr/lib/gcc/
[CI_JOB_NAME=x86_64-gnu-llvm-17]
##[group]Clock drift check
  local time: Wed Mar 20 19:14:50 UTC 2024
  network time: Wed, 20 Mar 2024 19:14:50 GMT
  network time: Wed, 20 Mar 2024 19:14:50 GMT
##[endgroup]
sccache: Starting the server...
##[group]Configure the build
configure: processing command line
configure: 
configure: build.configure-args := ['--build=x86_64-unknown-linux-gnu', '--llvm-root=/usr/lib/llvm-17', '--enable-llvm-link-shared', '--set', 'rust.thin-lto-import-instr-limit=10', '--set', 'change-id=99999999', '--enable-verbose-configure', '--enable-sccache', '--disable-manage-submodules', '--enable-locked-deps', '--enable-cargo-native-static', '--set', 'rust.codegen-units-std=1', '--set', 'dist.compression-profile=balanced', '--dist-compression-formats=xz', '--disable-dist-src', '--release-channel=nightly', '--enable-debug-assertions', '--enable-overflow-checks', '--enable-llvm-assertions', '--set', 'rust.verify-llvm-ir', '--set', 'rust.codegen-backends=llvm,cranelift,gcc', '--set', 'llvm.static-libstdcpp', '--enable-new-symbol-mangling']
configure: target.x86_64-unknown-linux-gnu.llvm-config := /usr/lib/llvm-17/bin/llvm-config
configure: llvm.link-shared     := True
configure: rust.thin-lto-import-instr-limit := 10
configure: change-id            := 99999999
---

---- [ui] tests/ui/consts/const-multi-ref.rs stdout ----
diff of stderr:

8    = help: add `#![feature(const_mut_refs)]` to the crate attributes to enable
9    = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date
- error[E0658]: cannot borrow here, since the borrowed element may contain interior mutability
-   --> $DIR/const-multi-ref.rs:16:13
-    |
- LL |     let p = &a;
- LL |     let p = &a;
-    |             ^^
-    |
-    = note: see issue #80384 <https://github.com/rust-lang/rust/issues/80384> for more information
-    = help: add `#![feature(const_refs_to_cell)]` to the crate attributes to enable
-    = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date
- error: aborting due to 2 previous errors
+ error: aborting due to 1 previous error
22 
23 For more information about this error, try `rustc --explain E0658`.
---
--- stderr -------------------------------
error[E0658]: mutable references are not allowed in constants
##[error]  --> /checkout/tests/ui/consts/const-multi-ref.rs:6:13
   |
LL |     let p = &mut a; //~ ERROR mutable references are not allowed in constants
   |
   = note: see issue #57349 <https://github.com/rust-lang/rust/issues/57349> for more information
   = help: add `#![feature(const_mut_refs)]` to the crate attributes to enable
   = help: add `#![feature(const_mut_refs)]` to the crate attributes to enable
   = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date
error: aborting due to 1 previous error

For more information about this error, try `rustc --explain E0658`.
------------------------------------------
---
   |
LL |     let x: &'static _ = &X;
   |            ----------    ^ creates a temporary value which is freed while still in use
   |            |
   |            type annotation requires that borrow lasts for `'static`
LL |     let y: &'static _ = &Y;
   | - temporary value is freed at the end of this statement

error[E0716]: temporary value dropped while borrowed
##[error]  --> /checkout/tests/ui/consts/const_let_promote.rs:16:26
##[error]  --> /checkout/tests/ui/consts/const_let_promote.rs:16:26
   |
LL |     let y: &'static _ = &Y;
   |            ----------    ^ creates a temporary value which is freed while still in use
   |            type annotation requires that borrow lasts for `'static`
LL | }
   | - temporary value is freed at the end of this statement

---
---- [ui] tests/ui/consts/future-incompat-mutable-in-final-value-issue-121610.rs stdout ----

error: test compilation failed although it shouldn't!
status: exit status: 1
command: RUSTC_ICE="0" "/checkout/obj/build/x86_64-unknown-linux-gnu/stage2/bin/rustc" "/checkout/tests/ui/consts/future-incompat-mutable-in-final-value-issue-121610.rs" "-Zthreads=1" "-Zsimulate-remapped-rust-src-base=/rustc/FAKE_PREFIX" "-Ztranslate-remapped-path-to-local-path=no" "-Z" "ignore-directory-in-diagnostics-source-blocks=/cargo" "--sysroot" "/checkout/obj/build/x86_64-unknown-linux-gnu/stage2" "--target=x86_64-unknown-linux-gnu" "--error-format" "json" "--json" "future-incompat" "-Ccodegen-units=1" "-Zui-testing" "-Zdeduplicate-diagnostics=no" "-Zwrite-long-types-to-disk=no" "-Cstrip=debuginfo" "--emit" "metadata" "-C" "prefer-dynamic" "--out-dir" "/checkout/obj/build/x86_64-unknown-linux-gnu/test/ui/consts/future-incompat-mutable-in-final-value-issue-121610" "-A" "unused" "-A" "internal_features" "-Crpath" "-Cdebuginfo=0" "-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/future-incompat-mutable-in-final-value-issue-121610/auxiliary"
--- stderr -------------------------------
error[E0492]: constants cannot refer to interior mutable data
##[error]  --> /checkout/tests/ui/consts/future-incompat-mutable-in-final-value-issue-121610.rs:13:29
   |
   |
LL | const UNDEFINED: &JsValue = &JsValue::Undefined;
   |                             ^^^^^^^^^^^^^^^^^^^ this borrow of an interior mutable value may end up in the final value
error: aborting due to 1 previous error

For more information about this error, try `rustc --explain E0492`.
------------------------------------------
---
--- stderr -------------------------------
error[E0716]: temporary value dropped while borrowed
##[error]  --> /checkout/tests/ui/consts/interior-mut-const-via-union.rs:37:26
   |
LL |     let _: &'static _ = &C;
   |            ----------    ^ creates a temporary value which is freed while still in use
   |            type annotation requires that borrow lasts for `'static`
LL | }
   | - temporary value is freed at the end of this statement

---
---- [ui] tests/ui/consts/issue-65348.rs stdout ----

error: test compilation failed although it shouldn't!
status: exit status: 1
command: RUSTC_ICE="0" "/checkout/obj/build/x86_64-unknown-linux-gnu/stage2/bin/rustc" "/checkout/tests/ui/consts/issue-65348.rs" "-Zthreads=1" "-Zsimulate-remapped-rust-src-base=/rustc/FAKE_PREFIX" "-Ztranslate-remapped-path-to-local-path=no" "-Z" "ignore-directory-in-diagnostics-source-blocks=/cargo" "--sysroot" "/checkout/obj/build/x86_64-unknown-linux-gnu/stage2" "--target=x86_64-unknown-linux-gnu" "--error-format" "json" "--json" "future-incompat" "-Ccodegen-units=1" "-Zui-testing" "-Zdeduplicate-diagnostics=no" "-Zwrite-long-types-to-disk=no" "-Cstrip=debuginfo" "--emit" "metadata" "-C" "prefer-dynamic" "--out-dir" "/checkout/obj/build/x86_64-unknown-linux-gnu/test/ui/consts/issue-65348" "-A" "unused" "-A" "internal_features" "-Crpath" "-Cdebuginfo=0" "-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/issue-65348/auxiliary"
--- stderr -------------------------------
error[E0515]: cannot return reference to temporary value
##[error]  --> /checkout/tests/ui/consts/issue-65348.rs:13:5
   |
   |
LL |     &Generic::<T>::ARRAY[0]
   |     ^-------------------^^^
   |     |temporary value created here
   |     returns a reference to data owned by the current function

error[E0515]: cannot return reference to temporary value
error[E0515]: cannot return reference to temporary value
##[error]  --> /checkout/tests/ui/consts/issue-65348.rs:17:5
   |
LL |     &Generic::<T>::NEWTYPE_ARRAY.0[0]
   |     ^---------------------------^^^^^
   |     |temporary value created here
   |     returns a reference to data owned by the current function

error[E0515]: cannot return reference to temporary value
error[E0515]: cannot return reference to temporary value
##[error]  --> /checkout/tests/ui/consts/issue-65348.rs:21:5
   |
LL |     &(Generic::<T>::ARRAY_FIELD.0).1[0]
   |     ^^-------------------------^^^^^^^^
   |     | temporary value created here
   |     returns a reference to data owned by the current function

error: aborting due to 3 previous errors
---
--- stderr -------------------------------
error[E0716]: temporary value dropped while borrowed
##[error]  --> /checkout/tests/ui/consts/promoted-storage.rs:19:26
   |
LL |     let _: &'static _ = &C;
   |            ----------    ^ creates a temporary value which is freed while still in use
   |            type annotation requires that borrow lasts for `'static`
LL | }
   | - temporary value is freed at the end of this statement

---
-   --> $DIR/promote-not.rs:40:29
+ error[E0080]: it is undefined behavior to use this value
+   --> $DIR/promote-not.rs:38:1
33    |
+ LL | const TEST_INTERIOR_MUT: () = {
+    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^ constructing invalid value at .<deref>.0.value: encountered `UnsafeCell` in read-only memory
+    |
+    = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rustc repository if you believe it should not be considered undefined behavior.
+    = note: the raw bytes of the constant (size: 8, align: 8) {
+            }
+ 
+ note: erroneous constant encountered
+   --> $DIR/promote-not.rs:40:28
+   --> $DIR/promote-not.rs:40:28
+    |
34 LL |     let _val: &'static _ = &(Cell::new(1), 2).1;
-    |               ----------    ^^^^^^^^^^^^^^^^^ creates a temporary value which is freed while still in use
-    |               type annotation requires that borrow lasts for `'static`
- LL | };
-    | - temporary value is freed at the end of this statement
+    |                            ^^^^^^^^^^^^^^^^^^^^
---
--- stderr -------------------------------
error[E0716]: temporary value dropped while borrowed
##[error]  --> /checkout/tests/ui/consts/promote-not.rs:9:50
   |
LL | static mut TEST1: Option<&mut [i32]> = Some(&mut [1, 2, 3]); //~ ERROR temporary value dropped while borrowed
   |                                        |         |        |
   |                                        |         |        temporary value is freed at the end of this statement
   |                                        |         creates a temporary value which is freed while still in use
   |                                        using this value as a static requires that borrow lasts for `'static`
   |                                        using this value as a static requires that borrow lasts for `'static`

error[E0716]: temporary value dropped while borrowed
##[error]  --> /checkout/tests/ui/consts/promote-not.rs:12:18
   |
LL |     let x = &mut [1,2,3]; //~ ERROR temporary value dropped while borrowed
   |                  ^^^^^^^ creates a temporary value which is freed while still in use
   |     - using this value as a static requires that borrow lasts for `'static`
LL | };
   | - temporary value is freed at the end of this statement


error[E0716]: temporary value dropped while borrowed
##[error]  --> /checkout/tests/ui/consts/promote-not.rs:34:29
   |
LL |     let _x: &'static i32 = &unsafe { U { x: 0 }.x }; //~ ERROR temporary value dropped while borrowed
   |             ------------    ^^^^^^^^^^^^^^^^^^^^^^^ creates a temporary value which is freed while still in use
   |             type annotation requires that borrow lasts for `'static`
LL | };
   | - temporary value is freed at the end of this statement


error[E0080]: it is undefined behavior to use this value
##[error]  --> /checkout/tests/ui/consts/promote-not.rs:38:1
   |
LL | const TEST_INTERIOR_MUT: () = {
   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^ constructing invalid value at .<deref>.0.value: encountered `UnsafeCell` in read-only memory
   |
   = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rustc repository if you believe it should not be considered undefined behavior.
   = note: the raw bytes of the constant (size: 8, align: 8) {
           }

note: erroneous constant encountered
  --> /checkout/tests/ui/consts/promote-not.rs:40:28
  --> /checkout/tests/ui/consts/promote-not.rs:40:28
   |
LL |     let _val: &'static _ = &(Cell::new(1), 2).1; //~ ERROR temporary value dropped while borrowed

error[E0493]: destructor of `String` cannot be evaluated at compile-time
##[error]  --> /checkout/tests/ui/consts/promote-not.rs:47:14
   |
   |
LL |     let x = &String::new(); //~ ERROR destructor of `String` cannot be evaluated at compile-time
   |              ^^^^^^^^^^^^^ the destructor for this type cannot be evaluated in constants
LL | };
   | - value is dropped here

error[E0716]: temporary value dropped while borrowed
error[E0716]: temporary value dropped while borrowed
##[error]  --> /checkout/tests/ui/consts/promote-not.rs:21:32
   |
LL |         let _x: &'static () = &foo(); //~ ERROR temporary value dropped while borrowed
   |                 -----------    ^^^^^ creates a temporary value which is freed while still in use
   |                 type annotation requires that borrow lasts for `'static`
LL |     }
   |     - temporary value is freed at the end of this statement


error[E0716]: temporary value dropped while borrowed
##[error]  --> /checkout/tests/ui/consts/promote-not.rs:29:29
   |
LL |     let _x: &'static i32 = &unsafe { U { x: 0 }.x }; //~ ERROR temporary value dropped while borrowed
   |             ------------    ^^^^^^^^^^^^^^^^^^^^^^^ creates a temporary value which is freed while still in use
   |             type annotation requires that borrow lasts for `'static`
LL | }
   | - temporary value is freed at the end of this statement


error[E0716]: temporary value dropped while borrowed
##[error]  --> /checkout/tests/ui/consts/promote-not.rs:56:29
   |
LL |     let _val: &'static _ = &(Cell::new(1), 2).0; //~ ERROR temporary value dropped while borrowed
   |               ----------    ^^^^^^^^^^^^^^^^^ creates a temporary value which is freed while still in use
   |               type annotation requires that borrow lasts for `'static`
...
LL | }
   | - temporary value is freed at the end of this statement
   | - temporary value is freed at the end of this statement

error[E0716]: temporary value dropped while borrowed
##[error]  --> /checkout/tests/ui/consts/promote-not.rs:57:29
   |
LL |     let _val: &'static _ = &(Cell::new(1), 2).1; //~ ERROR temporary value dropped while borrowed
   |               ----------    ^^^^^^^^^^^^^^^^^ creates a temporary value which is freed while still in use
   |               type annotation requires that borrow lasts for `'static`
...
LL | }
   | - temporary value is freed at the end of this statement
   | - temporary value is freed at the end of this statement

error[E0716]: temporary value dropped while borrowed
##[error]  --> /checkout/tests/ui/consts/promote-not.rs:60:29
   |
LL |     let _val: &'static _ = &(1/0); //~ ERROR temporary value dropped while borrowed
   |               ----------    ^^^^^ creates a temporary value which is freed while still in use
   |               type annotation requires that borrow lasts for `'static`
...
LL | }
   | - temporary value is freed at the end of this statement
   | - temporary value is freed at the end of this statement

error[E0716]: temporary value dropped while borrowed
##[error]  --> /checkout/tests/ui/consts/promote-not.rs:61:29
   |
LL |     let _val: &'static _ = &(1/(1-1)); //~ ERROR temporary value dropped while borrowed
   |               ----------    ^^^^^^^^^ creates a temporary value which is freed while still in use
   |               type annotation requires that borrow lasts for `'static`
...
LL | }
   | - temporary value is freed at the end of this statement
   | - temporary value is freed at the end of this statement

error[E0716]: temporary value dropped while borrowed
##[error]  --> /checkout/tests/ui/consts/promote-not.rs:62:29
   |
LL |     let _val: &'static _ = &((1+1)/(1-1)); //~ ERROR temporary value dropped while borrowed
   |               ----------    ^^^^^^^^^^^^^ creates a temporary value which is freed while still in use
   |               type annotation requires that borrow lasts for `'static`
...
LL | }
   | - temporary value is freed at the end of this statement
   | - temporary value is freed at the end of this statement

error[E0716]: temporary value dropped while borrowed
##[error]  --> /checkout/tests/ui/consts/promote-not.rs:63:29
   |
LL |     let _val: &'static _ = &(i32::MIN/-1); //~ ERROR temporary value dropped while borrowed
   |               ----------    ^^^^^^^^^^^^^ creates a temporary value which is freed while still in use
   |               type annotation requires that borrow lasts for `'static`
...
LL | }
   | - temporary value is freed at the end of this statement
   | - temporary value is freed at the end of this statement

error[E0716]: temporary value dropped while borrowed
##[error]  --> /checkout/tests/ui/consts/promote-not.rs:64:29
   |
LL |     let _val: &'static _ = &(i32::MIN/(0-1)); //~ ERROR temporary value dropped while borrowed
   |               ----------    ^^^^^^^^^^^^^^^^ creates a temporary value which is freed while still in use
   |               type annotation requires that borrow lasts for `'static`
...
LL | }
   | - temporary value is freed at the end of this statement
   | - temporary value is freed at the end of this statement

error[E0716]: temporary value dropped while borrowed
##[error]  --> /checkout/tests/ui/consts/promote-not.rs:65:29
   |
LL |     let _val: &'static _ = &(-128i8/-1); //~ ERROR temporary value dropped while borrowed
   |               ----------    ^^^^^^^^^^^ creates a temporary value which is freed while still in use
   |               type annotation requires that borrow lasts for `'static`
...
LL | }
   | - temporary value is freed at the end of this statement
   | - temporary value is freed at the end of this statement

error[E0716]: temporary value dropped while borrowed
##[error]  --> /checkout/tests/ui/consts/promote-not.rs:66:29
   |
LL |     let _val: &'static _ = &(1%0); //~ ERROR temporary value dropped while borrowed
   |               ----------    ^^^^^ creates a temporary value which is freed while still in use
   |               type annotation requires that borrow lasts for `'static`
...
LL | }
   | - temporary value is freed at the end of this statement
   | - temporary value is freed at the end of this statement

error[E0716]: temporary value dropped while borrowed
##[error]  --> /checkout/tests/ui/consts/promote-not.rs:67:29
   |
LL |     let _val: &'static _ = &(1%(1-1)); //~ ERROR temporary value dropped while borrowed
   |               ----------    ^^^^^^^^^ creates a temporary value which is freed while still in use
   |               type annotation requires that borrow lasts for `'static`
...
LL | }
   | - temporary value is freed at the end of this statement
   | - temporary value is freed at the end of this statement

error[E0716]: temporary value dropped while borrowed
##[error]  --> /checkout/tests/ui/consts/promote-not.rs:68:29
   |
LL |     let _val: &'static _ = &([1,2,3][4]+1); //~ ERROR temporary value dropped while borrowed
   |               ----------    ^^^^^^^^^^^^^^ creates a temporary value which is freed while still in use
   |               type annotation requires that borrow lasts for `'static`
...
LL | }
   | - temporary value is freed at the end of this statement
   | - temporary value is freed at the end of this statement

error[E0716]: temporary value dropped while borrowed
##[error]  --> /checkout/tests/ui/consts/promote-not.rs:72:29
   |
LL |     let _val: &'static _ = &TEST_DROP;
   |               ----------    ^^^^^^^^^ creates a temporary value which is freed while still in use
   |               type annotation requires that borrow lasts for `'static`
...
LL | }
   | - temporary value is freed at the end of this statement
   | - temporary value is freed at the end of this statement

error[E0716]: temporary value dropped while borrowed
##[error]  --> /checkout/tests/ui/consts/promote-not.rs:74:29
   |
LL |     let _val: &'static _ = &&TEST_DROP;
   |               ----------    ^^^^^^^^^^ creates a temporary value which is freed while still in use
   |               type annotation requires that borrow lasts for `'static`
...
LL | }
   | - temporary value is freed at the end of this statement
   | - temporary value is freed at the end of this statement

error[E0716]: temporary value dropped while borrowed
##[error]  --> /checkout/tests/ui/consts/promote-not.rs:74:30
   |
LL |     let _val: &'static _ = &&TEST_DROP;
   |               ----------     ^^^^^^^^^ creates a temporary value which is freed while still in use
   |               type annotation requires that borrow lasts for `'static`
...
LL | }
   | - temporary value is freed at the end of this statement
   | - temporary value is freed at the end of this statement

error[E0716]: temporary value dropped while borrowed
##[error]  --> /checkout/tests/ui/consts/promote-not.rs:77:29
   |
LL |     let _val: &'static _ = &(&TEST_DROP,);
   |               ----------    ^^^^^^^^^^^^^ creates a temporary value which is freed while still in use
   |               type annotation requires that borrow lasts for `'static`
...
LL | }
   | - temporary value is freed at the end of this statement
   | - temporary value is freed at the end of this statement

error[E0716]: temporary value dropped while borrowed
##[error]  --> /checkout/tests/ui/consts/promote-not.rs:77:31
   |
LL |     let _val: &'static _ = &(&TEST_DROP,);
   |               ----------      ^^^^^^^^^ creates a temporary value which is freed while still in use
   |               type annotation requires that borrow lasts for `'static`
...
LL | }
   | - temporary value is freed at the end of this statement
   | - temporary value is freed at the end of this statement

error[E0716]: temporary value dropped while borrowed
##[error]  --> /checkout/tests/ui/consts/promote-not.rs:80:29
   |
LL |     let _val: &'static _ = &[&TEST_DROP; 1];
   |               ----------    ^^^^^^^^^^^^^^^ creates a temporary value which is freed while still in use
   |               type annotation requires that borrow lasts for `'static`
...
LL | }
   | - temporary value is freed at the end of this statement
   | - temporary value is freed at the end of this statement

error[E0716]: temporary value dropped while borrowed
##[error]  --> /checkout/tests/ui/consts/promote-not.rs:80:31
   |
LL |     let _val: &'static _ = &[&TEST_DROP; 1];
   |               |               |
   |               |               creates a temporary value which is freed while still in use
   |               type annotation requires that borrow lasts for `'static`


error[E0716]: temporary value dropped while borrowed
##[error]  --> /checkout/tests/ui/consts/promote-not.rs:89:26
   |
LL |     let x: &'static _ = &UnionWithCell { f1: 0 };
   |            ----------    ^^^^^^^^^^^^^^^^^^^^^^^ creates a temporary value which is freed while still in use
   |            type annotation requires that borrow lasts for `'static`
   |            type annotation requires that borrow lasts for `'static`
LL |     //~^ ERROR temporary value dropped while borrowed
   | - temporary value is freed at the end of this statement

error: aborting due to 26 previous errors

---

---- [ui] tests/ui/consts/refs-to-cell-in-final.rs stdout ----
diff of stderr:

12 LL | const RAW_SYNC_C: SyncPtr<Cell<i32>> = SyncPtr { x: &Cell::new(42) };
13    |                                                     ^^^^^^^^^^^^^^ this borrow of an interior mutable value may end up in the final value
- warning: encountered mutable pointer in final value of constant
-   --> $DIR/refs-to-cell-in-final.rs:30:1
+ error[E0492]: constants cannot refer to interior mutable data
+   --> $DIR/refs-to-cell-in-final.rs:30:29
+   --> $DIR/refs-to-cell-in-final.rs:30:29
17    |
18 LL | const UNDEFINED: &JsValue = &JsValue::Undefined;
-    | ^^^^^^^^^^^^^^^^^^^^^^^^^
+    |                             ^^^^^^^^^^^^^^^^^^^ this borrow of an interior mutable value may end up in the final value
+ error[E0492]: constants cannot refer to interior mutable data
+   --> $DIR/refs-to-cell-in-final.rs:35:42
20    |
-    = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
-    = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
-    = note: for more information, see issue #122153 <https://github.com/rust-lang/rust/issues/122153>
-    = note: `#[warn(const_eval_mutable_ptr_in_final_value)]` on by default
+ LL | const NONE: &'static Option<Cell<i32>> = &None;
+    |                                          ^^^^^ this borrow of an interior mutable value may end up in the final value
- error: aborting due to 2 previous errors; 1 warning emitted
- 
- For more information about this error, try `rustc --explain E0492`.
- Future incompatibility report: Future breakage diagnostic:
- Future incompatibility report: Future breakage diagnostic:
- warning: encountered mutable pointer in final value of constant
-   --> $DIR/refs-to-cell-in-final.rs:30:1
+ error[E0716]: temporary value dropped while borrowed
+   --> $DIR/refs-to-cell-in-final.rs:38:14
31    |
- LL | const UNDEFINED: &JsValue = &JsValue::Undefined;
-    |
-    = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
-    = note: for more information, see issue #122153 <https://github.com/rust-lang/rust/issues/122153>
-    = note: `#[warn(const_eval_mutable_ptr_in_final_value)]` on by default
-    = note: `#[warn(const_eval_mutable_ptr_in_final_value)]` on by default
+ LL |     let x = &None;
+    |              ^^^^ creates a temporary value which is freed while still in use
+ LL |     x
+    |     - using this value as a constant requires that borrow lasts for `'static`
+ LL | };
+    | - temporary value is freed at the end of this statement
+ error: aborting due to 5 previous errors
+ 
+ Some errors have detailed explanations: E0492, E0716.
+ For more information about an error, try `rustc --explain E0492`.
---
--- stderr -------------------------------
error[E0492]: statics cannot refer to interior mutable data
##[error]  --> /checkout/tests/ui/consts/refs-to-cell-in-final.rs:13:54
   |
LL | static RAW_SYNC_S: SyncPtr<Cell<i32>> = SyncPtr { x: &Cell::new(42) };
   |                                                      ^^^^^^^^^^^^^^ this borrow of an interior mutable value may end up in the final value
   = help: to fix this, the value can be extracted to a separate `static` item and then referenced

error[E0492]: constants cannot refer to interior mutable data
##[error]  --> /checkout/tests/ui/consts/refs-to-cell-in-final.rs:15:53
##[error]  --> /checkout/tests/ui/consts/refs-to-cell-in-final.rs:15:53
   |
LL | const RAW_SYNC_C: SyncPtr<Cell<i32>> = SyncPtr { x: &Cell::new(42) };
   |                                                     ^^^^^^^^^^^^^^ this borrow of an interior mutable value may end up in the final value
error[E0492]: constants cannot refer to interior mutable data
##[error]  --> /checkout/tests/ui/consts/refs-to-cell-in-final.rs:30:29
   |
   |
LL | const UNDEFINED: &JsValue = &JsValue::Undefined;
   |                             ^^^^^^^^^^^^^^^^^^^ this borrow of an interior mutable value may end up in the final value
error[E0492]: constants cannot refer to interior mutable data
Build completed unsuccessfully in 0:14:00
##[error]  --> /checkout/tests/ui/consts/refs-to-cell-in-final.rs:35:42
   |
   |
LL | const NONE: &'static Option<Cell<i32>> = &None;
   |                                          ^^^^^ this borrow of an interior mutable value may end up in the final value
error[E0716]: temporary value dropped while borrowed
##[error]  --> /checkout/tests/ui/consts/refs-to-cell-in-final.rs:38:14
   |
   |
LL |     let x = &None;
   |              ^^^^ creates a temporary value which is freed while still in use
   |     - using this value as a constant requires that borrow lasts for `'static`
LL | };
   | - temporary value is freed at the end of this statement

---
--- stderr -------------------------------
error[E0716]: temporary value dropped while borrowed
##[error]  --> /checkout/tests/ui/consts/rvalue-static-promotion.rs:17:45
   |
LL |     let _: &'static Option<Cell<String>> = &NONE_CELL_STRING;
   |            -----------------------------    ^^^^^^^^^^^^^^^^ creates a temporary value which is freed while still in use
   |            type annotation requires that borrow lasts for `'static`
   |            type annotation requires that borrow lasts for `'static`
LL |     let _: &'static Option<Box<()>> = &Foo::FOO;
   | - temporary value is freed at the end of this statement

error: aborting due to 1 previous error

---
- error: aborting due to 2 previous errors
+ error[E0492]: constants cannot refer to interior mutable data
+   --> $DIR/E0492.rs:7:44
+    |
+ LL | const NONE: &'static Option<AtomicUsize> = &None;
+    |                                            ^^^^^ this borrow of an interior mutable value may end up in the final value
+ error: aborting due to 3 previous errors
16 
17 For more information about this error, try `rustc --explain E0492`.
18 
---
To only update this specific test, also pass `--test-args error-codes/E0492.rs`

error: 1 errors occurred comparing output.
status: exit status: 1
command: RUSTC_ICE="0" "/checkout/obj/build/x86_64-unknown-linux-gnu/stage2/bin/rustc" "/checkout/tests/ui/error-codes/E0492.rs" "-Zthreads=1" "-Zsimulate-remapped-rust-src-base=/rustc/FAKE_PREFIX" "-Ztranslate-remapped-path-to-local-path=no" "-Z" "ignore-directory-in-diagnostics-source-blocks=/cargo" "--sysroot" "/checkout/obj/build/x86_64-unknown-linux-gnu/stage2" "--target=x86_64-unknown-linux-gnu" "--error-format" "json" "--json" "future-incompat" "-Ccodegen-units=1" "-Zui-testing" "-Zdeduplicate-diagnostics=no" "-Zwrite-long-types-to-disk=no" "-Cstrip=debuginfo" "--emit" "metadata" "-C" "prefer-dynamic" "--out-dir" "/checkout/obj/build/x86_64-unknown-linux-gnu/test/ui/error-codes/E0492" "-A" "unused" "-A" "internal_features" "-Crpath" "-Cdebuginfo=0" "-Lnative=/checkout/obj/build/x86_64-unknown-linux-gnu/native/rust-test-helpers" "-L" "/checkout/obj/build/x86_64-unknown-linux-gnu/test/ui/error-codes/E0492/auxiliary"
--- stderr -------------------------------
error[E0492]: constants cannot refer to interior mutable data
##[error]  --> /checkout/tests/ui/error-codes/E0492.rs:4:33
   |
   |
LL | const B: &'static AtomicUsize = &A; //~ ERROR E0492
   |                                 ^^ this borrow of an interior mutable value may end up in the final value
error[E0492]: statics cannot refer to interior mutable data
##[error]  --> /checkout/tests/ui/error-codes/E0492.rs:5:34
   |
   |
LL | static C: &'static AtomicUsize = &A; //~ ERROR E0492
   |                                  ^^ this borrow of an interior mutable value may end up in the final value
   = help: to fix this, the value can be extracted to a separate `static` item and then referenced

error[E0492]: constants cannot refer to interior mutable data
##[error]  --> /checkout/tests/ui/error-codes/E0492.rs:7:44
##[error]  --> /checkout/tests/ui/error-codes/E0492.rs:7:44
   |
LL | const NONE: &'static Option<AtomicUsize> = &None;
   |                                            ^^^^^ this borrow of an interior mutable value may end up in the final value
error: aborting due to 3 previous errors

For more information about this error, try `rustc --explain E0492`.
------------------------------------------
------------------------------------------


---- [ui] tests/ui/rfcs/rfc-2632-const-trait-impl/effects/ice-112822-expected-type-for-param.rs stdout ----
diff of stderr:

23    = help: the trait `~const PartialEq<&u8>` is not implemented for `&u8`
24    = note: this error originates in the macro `assert_eq` (in Nightly builds, run with -Z macro-backtrace for more info)
25 
- error[E0391]: cycle detected when computing type of opaque `test::{opaque#0}`
-   --> $DIR/ice-112822-expected-type-for-param.rs:3:20
-    |
- LL | const fn test() -> impl ~const Fn() {
-    |
-    |
- note: ...which requires borrow-checking `test`...
-   --> $DIR/ice-112822-expected-type-for-param.rs:3:1
-    |
- LL | const fn test() -> impl ~const Fn() {
-    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
- note: ...which requires promoting constants in MIR for `test`...
-   --> $DIR/ice-112822-expected-type-for-param.rs:3:1
-    |
- LL | const fn test() -> impl ~const Fn() {
-    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
- note: ...which requires const checking `test`...
-   --> $DIR/ice-112822-expected-type-for-param.rs:3:1
-    |
- LL | const fn test() -> impl ~const Fn() {
-    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
-    = note: ...which requires computing whether `test::{opaque#0}` is freeze...
-    = note: ...which requires evaluating trait selection obligation `test::{opaque#0}: core::marker::Freeze`...
-    = note: ...which again requires computing type of opaque `test::{opaque#0}`, completing the cycle
- note: cycle used when computing type of `test::{opaque#0}`
-   --> $DIR/ice-112822-expected-type-for-param.rs:3:20
-    |
- LL | const fn test() -> impl ~const Fn() {
-    |                    ^^^^^^^^^^^^^^^^
-    = note: see https://rustc-dev-guide.rust-lang.org/overview.html#queries and https://rustc-dev-guide.rust-lang.org/query.html for more information
56 
- error: aborting due to 4 previous errors
- 
- Some errors have detailed explanations: E0277, E0391, E0658.
---

The actual stderr differed from the expected stderr.
Actual stderr saved to /checkout/obj/build/x86_64-unknown-linux-gnu/test/ui/rfcs/rfc-2632-const-trait-impl/effects/ice-112822-expected-type-for-param/ice-112822-expected-type-for-param.stderr
To update references, rerun the tests and pass the `--bless` flag
To only update this specific test, also pass `--test-args rfcs/rfc-2632-const-trait-impl/effects/ice-112822-expected-type-for-param.rs`
error: 1 errors occurred comparing output.
status: exit status: 1
command: RUSTC_ICE="0" "/checkout/obj/build/x86_64-unknown-linux-gnu/stage2/bin/rustc" "/checkout/tests/ui/rfcs/rfc-2632-const-trait-impl/effects/ice-112822-expected-type-for-param.rs" "-Zthreads=1" "-Zsimulate-remapped-rust-src-base=/rustc/FAKE_PREFIX" "-Ztranslate-remapped-path-to-local-path=no" "-Z" "ignore-directory-in-diagnostics-source-blocks=/cargo" "--sysroot" "/checkout/obj/build/x86_64-unknown-linux-gnu/stage2" "--target=x86_64-unknown-linux-gnu" "--error-format" "json" "--json" "future-incompat" "-Ccodegen-units=1" "-Zui-testing" "-Zdeduplicate-diagnostics=no" "-Zwrite-long-types-to-disk=no" "-Cstrip=debuginfo" "--emit" "metadata" "-C" "prefer-dynamic" "--out-dir" "/checkout/obj/build/x86_64-unknown-linux-gnu/test/ui/rfcs/rfc-2632-const-trait-impl/effects/ice-112822-expected-type-for-param" "-A" "unused" "-A" "internal_features" "-Crpath" "-Cdebuginfo=0" "-Lnative=/checkout/obj/build/x86_64-unknown-linux-gnu/native/rust-test-helpers" "-L" "/checkout/obj/build/x86_64-unknown-linux-gnu/test/ui/rfcs/rfc-2632-const-trait-impl/effects/ice-112822-expected-type-for-param/auxiliary"
stdout: none
stdout: none
--- stderr -------------------------------
error[E0658]: const closures are experimental
##[error]  --> /checkout/tests/ui/rfcs/rfc-2632-const-trait-impl/effects/ice-112822-expected-type-for-param.rs:5:5
   |
LL |     const move || { //~ ERROR const closures are experimental
   |
   = note: see issue #106003 <https://github.com/rust-lang/rust/issues/106003> for more information
   = help: add `#![feature(const_closures)]` to the crate attributes to enable
   = help: add `#![feature(const_closures)]` to the crate attributes to enable
   = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date

error: `~const` can only be applied to `#[const_trait]` traits
   |
   |
LL | const fn test() -> impl ~const Fn() { //~ ERROR `~const` can only be applied to `#[const_trait]` traits


error[E0277]: can't compare `&u8` with `&u8`
   |
   |
LL |                 assert_eq!(first, &b'f');
   |                 ^^^^^^^^^^^^^^^^^^^^^^^^ no implementation for `&u8 == &u8`
   |
   = help: the trait `~const PartialEq<&u8>` is not implemented for `&u8`
   = note: this error originates in the macro `assert_eq` (in Nightly builds, run with -Z macro-backtrace for more info)
error: aborting due to 3 previous errors

Some errors have detailed explanations: E0277, E0658.
For more information about an error, try `rustc --explain E0277`.
For more information about an error, try `rustc --explain E0277`.
------------------------------------------


---- [ui] tests/ui/unsafe/ranged_ints3_const.rs stdout ----
diff of stderr:

6    |
7    = note: references to fields of layout constrained fields lose the constraints. Coupled with interior mutability, the field can be changed to invalid values
- error[E0658]: cannot borrow here, since the borrowed element may contain interior mutability
-   --> $DIR/ranged_ints3_const.rs:12:13
-    |
-    |
- LL |     let y = &x.0;
-    |
-    = note: see issue #80384 <https://github.com/rust-lang/rust/issues/80384> for more information
-    = help: add `#![feature(const_refs_to_cell)]` to the crate attributes to enable
-    = help: add `#![feature(const_refs_to_cell)]` to the crate attributes to enable
-    = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date
18 
- error[E0658]: cannot borrow here, since the borrowed element may contain interior mutability
-   --> $DIR/ranged_ints3_const.rs:19:22
-    |
-    |
- LL |     let y = unsafe { &x.0 };
-    |
-    = note: see issue #80384 <https://github.com/rust-lang/rust/issues/80384> for more information
-    = help: add `#![feature(const_refs_to_cell)]` to the crate attributes to enable
-    = help: add `#![feature(const_refs_to_cell)]` to the crate attributes to enable
-    = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date
- error: aborting due to 3 previous errors
- 
- Some errors have detailed explanations: E0133, E0658.
- For more information about an error, try `rustc --explain E0133`.
---
--- stderr -------------------------------
error[E0133]: borrow of layout constrained field with interior mutability is unsafe and requires unsafe function or block
##[error]  --> /checkout/tests/ui/unsafe/ranged_ints3_const.rs:12:13
   |
LL |     let y = &x.0; //~ ERROR the borrowed element may contain interior mutability
   |             ^^^^ borrow of layout constrained field with interior mutability
   |
   = note: references to fields of layout constrained fields lose the constraints. Coupled with interior mutability, the field can be changed to invalid values
error: aborting due to 1 previous error

For more information about this error, try `rustc --explain E0133`.
------------------------------------------

bors · 2024-03-20T20:46:54Z

☀️ Try build successful - checks-actions
Build commit: cb4bf0e (cb4bf0ee9ea9dac86332c9e48c07269c7edc21dc)

RalfJung · 2024-03-20T21:08:55Z

@craterbot check

craterbot · 2024-03-20T21:09:01Z

👌 Experiment pr-122789 created and queued.
🤖 Automatically detected try build cb4bf0e
🔍 You can check out the queue and this experiment's details.

ℹ️ Crater is a tool to run experiments across parts of the Rust ecosystem. Learn more

craterbot · 2024-03-29T20:33:17Z

🚧 Experiment pr-122789 is now running

ℹ️ Crater is a tool to run experiments across parts of the Rust ecosystem. Learn more

craterbot · 2024-03-31T11:44:09Z

🎉 Experiment pr-122789 is completed!
📊 3823 regressed and 3 fixed (429092 total)
📰 Open the full report.

⚠️ If you notice any spurious failure please add them to the blacklist!
ℹ️ Crater is a tool to run experiments across parts of the Rust ecosystem. Learn more

RalfJung · 2024-03-31T11:49:39Z

Well I think that answers the question. ;)

rustbot assigned wesleywiser Mar 20, 2024

rustbot added S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. T-compiler Relevant to the compiler team, which will review and decide on the PR/issue. labels Mar 20, 2024

RalfJung added 2 commits March 20, 2024 20:11

experiment: remove value-based reasoning for interior mutability

5fcfa51

fix rustc build for new promotion rules

3660dd9

RalfJung force-pushed the interior-mut-experiment branch from 9051c32 to 3660dd9 Compare March 20, 2024 19:12

RalfJung marked this pull request as draft March 20, 2024 19:12

RalfJung unassigned wesleywiser Mar 20, 2024

RalfJung removed the S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. label Mar 20, 2024

Nadrieril reviewed Mar 20, 2024

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craterbot added the S-waiting-on-crater Status: Waiting on a crater run to be completed. label Mar 20, 2024

craterbot added S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. and removed S-waiting-on-crater Status: Waiting on a crater run to be completed. labels Mar 31, 2024

RalfJung mentioned this pull request Mar 31, 2024

regression: encountered mutable pointer in final value when "outer scope" rule applies in const/static with interior mutability #121610

Open

RalfJung closed this Mar 31, 2024

RalfJung mentioned this pull request Mar 31, 2024

Promotion introduces UB into otherwise well-defined code rust-lang/unsafe-code-guidelines#493

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RalfJung deleted the interior-mut-experiment branch March 31, 2024 11:54

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experiment: remove value-based reasoning for interior mutability #122789

experiment: remove value-based reasoning for interior mutability #122789

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experiment: remove value-based reasoning for interior mutability #122789

experiment: remove value-based reasoning for interior mutability #122789

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