replace box_new with lower-level intrinsics #148190

RalfJung · 2025-10-27T21:27:43Z

The box_new intrinsic is super special: during THIR construction it turns into an ExprKind::Box (formerly known as the box keyword), which then during MIR building turns into a special instruction sequence that invokes the exchange_malloc lang item (which has a name from a different time) and a special MIR statement to represent a shallowly-initialized Box (which raises interesting opsem questions).

This PR is the n-th attempt to get rid of box_new. That's non-trivial because it usually causes a perf regression: replacing box_new by naive unsafe code will incur extra copies in debug builds, making the resulting binaries a lot slower, and will generate a lot more MIR, making compilation measurably slower. Furthermore, vec! is a macro, so the exact code it expands to is highly relevant for borrow checking, type inference, and temporary scopes.

To avoid those problems, this PR does its best to make the MIR almost exactly the same as what it was before. box_new is used in two places, Box::new and vec!:

For Box::new that is fairly easy: the move_by_value intrinsic is basically all we need. However, to avoid the extra copy that would usually be generated for the argument of a function call, we need to special-case this intrinsic during MIR building. That's what the first commit does.
vec! is a lot more tricky. As a macro, its details leak to stable code, so almost every variant I tried broke either type inference or the lifetimes of temporaries in some ui test or ended up accepting unsound code due to the borrow checker not enforcing all the constraints I hoped it would enforce. I ended up with a variant that involves a new intrinsic, fn write_box_via_move<T>(b: Box<MaybeUninit<T>>, x: T) -> Box<MaybeUninit<T>>, that writes a value into a Box<MaybeUninit<T>> and returns that box again. The MIR building code for this is non-trivial, but in exchange we can get rid of somewhat similar code in the lowering for ExprKind::Box. Sadly, we need a new lang item as I found no other way to get a pointer of the right type in MIR, but we do get rid of the exchange_malloc lang item in exchange. (We can also get rid of Rvalue::ShallowInitBox; I didn't include that in this PR -- I think @cjgillot has a commit for this somewhere.)

See here for the latest perf numbers. Most of the regressions are in deep-vector which consists entirely of an invocation of vec!, so any change to that macro affects this benchmark disproportionally.

This is my first time even looking at MIR building code, so I am very low confidence in that part of the patch, in particular when it comes to scopes and drops and things like that.

`vec!` FAQ

Why does write_box_via_move return the Box again? Because we need to expand vec! to a bunch of method invocations without any blocks or let-statements, or else the temporary scopes (and type inference) don't work out.
Why is box_uninit_array_into_vec_unsafe (unsoundly!) a safe function? Because we can't use an unsafe block in vec! as that would necessarily also include the $x (due to it all being one big method invocation) and therefore interpret the user's code as being inside unsafe, which would be bad (and 10 years later, we still don't have safe blocks for macros like this).
Why does write_box_via_move use Box as input/output type, and not, say, raw pointers? Because that is the only way to get the correct behavior when $x panics or has control effects: we need the Box to be dropped in that case. (As a nice side-effect this also makes the intrinsic safe, which is imported as explained in the previous bullet.)
Why is there a lang item just to convert from *mut Box<MaybeUninit<T>> to *mut T? Because we need to do that conversion when compiling write_box_via_move to MIR, and we can't do that conversion in pure MIR. We can't transmute because then the borrow checker loses track of how the lifetimes flow through these calls, which would be unsound. We can't get the raw pointer out from inside the Box via field projections because that is a *const pointer which we can't write to. We can't cast that to *mut because then we again lose track of the lifetimes. We can't change that pointer to be *mut because then NonNull would have the wrong variance (and 10 years later, we still don't have variance annotations).
Can't we make it safe by having write_box_via_move return Box<T>? Yes we could, but there's no easy way for the intrinsic to convert its Box<MaybeUninit<T>> to a Box<T>. We would need another lang item.
Is this macro truly cursed? Yes, yes it is.

rustbot · 2025-10-27T21:27:47Z

Some changes occurred to MIR optimizations

cc @rust-lang/wg-mir-opt

The Miri subtree was changed

cc @rust-lang/miri

Some changes occurred in rustc_ty_utils::consts.rs

cc @BoxyUwU

Some changes occurred in match checking

cc @Nadrieril

rustbot · 2025-10-27T21:27:49Z

r? @SparrowLii

rustbot has assigned @SparrowLii.
They will have a look at your PR within the next two weeks and either review your PR or reassign to another reviewer.

Use r? to explicitly pick a reviewer

RalfJung · 2025-10-27T21:29:14Z

compiler/rustc_borrowck/src/type_check/mod.rs

+                        //         rvalue,
+                        //         "Unexpected CastKind::Transmute {ty_from:?} -> {ty:?}, which is not permitted in Analysis MIR",
+                        //     ),
+                        // }


This obviously needs to be resolved before landing... what should we do here? A transmute cast is always well-typed (it is UB if the sizes mismatch), so... can we just do nothing? I don't know what the type checker inside borrow checker is about.^^

MIR typeck exists to collect all the lifetime constraints for borrowck to check. It also acts as a little bit of a double-check that typechecking on HIR actually checked everything it was supposed to, in some sense it's kind of the "soundness critical typeck". Having this do nothing seems fine to me, there's nothing to really typeck here

Do we need to still visit the cast type to find any lifetimes in there, or so?

FWIW this "is not permitted in Analysis MIR" part in the error I am removing here is odd as this is not documented in the MIR syntax where we usually list such restrictions, and also not checked by the MIR validator.

Do we need to still visit the cast type to find any lifetimes in there, or so?

I don't think so, that should be handled by the super_rvalue call at the top of this visit_rvalue fn

I guess we do need to check something here, right now nothing enforces that the lifetimes match for the various uses of T in init_box_via_move<T>(b: Box<MaybeUninit<T>>, x: T) -> Box<T>.

RalfJung · 2025-10-27T21:30:52Z

compiler/rustc_mir_build/src/builder/expr/into.rs

+                        // Make sure `StorageDead` gets emitted.
+                        this.schedule_drop_storage_and_value(expr_span, this.local_scope(), ptr);


Here I am completely guessing... well really for all the changes in this file I am guessing, but the drop/storage scope stuff I know even less about than the rest of this.

RalfJung · 2025-10-27T21:31:18Z

compiler/rustc_mir_build/src/builder/expr/into.rs

+                            block,
+                            source_info,
+                            Place::from(ptr),
+                            // Needs to be a `Copy` so that `b` still gets dropped if `val` panics.


I added a Miri test to ensure the drop does indeed happen. That's the easiest way to check for memory leaks...

RalfJung · 2025-10-27T21:32:10Z

library/alloc/src/boxed.rs

+        // Nothing below can panic so we do not have to worry about deallocating `ptr`.
+        // SAFETY: we just allocated the box to store `x`.
+        unsafe { core::intrinsics::write_via_move(ptr, x) };
+        // SAFETY: we just initialized `b`.
+        unsafe { mem::transmute(ptr) }


I tried using init_box_via_move here instead and it makes things a bit slower in some secondary benchmarks. I have no idea why.

Do you mean write_box_via_move? Is the "bit slower" acceptable to simplify the implementation?

Should new_in and new_uninit_in get the same kind of inlined implementation?

Do you mean write_box_via_move?

Yeah. (I renamed that intrinsic since writing the comment.)

Is the "bit slower" acceptable to simplify the implementation?

It doesn't simplify it by much, does it? Also it clearly leaves write_box_via_move as a vec!-only hack which I like.

Should new_in and new_uninit_in get the same kind of inlined implementation?

That seems orthogonal to this PR. They didn't use box_new before and are not involved with vec! either.

RalfJung · 2025-10-27T21:33:50Z

...s/mir-opt/building/uniform_array_move_out.move_out_by_subslice.CleanupPostBorrowck.after.mir

This MIR is apparently so different from the previous one that it doesn't even show a diff (and the filename changed since I had to use CleanupPostBorrowck as built contains user types which contain super fragile DefIds). I have no idea what this test is testing and there are no filecheck annotations so... 😨

RalfJung · 2025-10-27T21:35:12Z

tests/mir-opt/dont_reset_cast_kind_without_updating_operand.test.GVN.64bit.panic-abort.diff

Are these changes fine? Who knows! At least the filecheck annotations in the test still pass.

This is a regression test for an ICE where GVN would cast with wrong types. We only check a cast, the rest is boilerplate from inlining.

RalfJung · 2025-10-27T21:38:30Z

tests/mir-opt/issue_62289.test.ElaborateDrops.before.panic-abort.mir

+        StorageDead(_10);
+        StorageDead(_8);
+        StorageDead(_4);
+        drop(_3) -> [return: bb10, unwind: bb15];


I think this is the relevant drop... but the before drop-elaboration MIR makes this quite hard to say. No idea why that's what the test checks. I think after drop elaboration this is a lot more obvious as the drops of moved-out variables are gone.

rustbot · 2025-10-28T07:22:52Z

This PR modifies tests/ui/issues/. If this PR is adding new tests to tests/ui/issues/,
please refrain from doing so, and instead add it to more descriptive subdirectories.

RalfJung · 2025-10-28T07:24:18Z

tests/ui/issues/issue-47184.rs

This is fully a duplicate of something already tested in nll/user-annotations/patterns.rs.

RalfJung · 2025-10-28T07:25:16Z

tests/ui/nll/user-annotations/patterns.rs

+    // FIXME: What is happening?!??
    let _: Vec<&'static String> = vec![&String::new()];
-    //~^ ERROR temporary value dropped while borrowed [E0716]

    let (_, a): (Vec<&'static String>, _) = (vec![&String::new()], 44);
-    //~^ ERROR temporary value dropped while borrowed [E0716]

    let (_a, b): (Vec<&'static String>, _) = (vec![&String::new()], 44);
-    //~^ ERROR temporary value dropped while borrowed [E0716]
 }


I have no idea what is happening here -- somehow code like let _: Vec<&'static String> = vec![&String::new()]; now compiles. I guess something is wrong with how I am lowering init_box_via_move?

It's probably related to the transmutes there. Is there some way to insert those in a way that the lifetime constraints still get enforced?

RalfJung · 2025-10-28T11:12:48Z

I can't think of any way to actually preserve these lifetimes while using transmutes... so we'll have to add more method calls to vec!, which will show up in perf. On the plus side it seems I misunderstood the errors I saw before regarding temporary scopes around vec!... or may our test suite just can't reproduce those problems.

So here's another redesign of the vec! macro. Macros were a mistake, and this one in particular has turned into my worst nightmare...

@bors try
@rust-timer queue

replace box_new with lower-level intrinsics

saethlin · 2025-11-04T16:02:24Z

@khuey you have contributed some great fixes to our debuginfo in the past, do you have any insight on what's happening with tests/debuginfo/macro-stepping.rs here?

khuey · 2025-11-04T21:53:17Z

fyi I'm out of the office today and can't look until later this week.

rustbot · 2025-11-04T22:57:09Z

Some changes occurred in diagnostic error codes

cc @GuillaumeGomez

RalfJung · 2025-11-05T10:56:51Z

I'm going to wait with fixing Clippy until we agree we even want this change.

Skgland · 2025-11-07T17:56:56Z

library/alloc/src/macros.rs

+        $crate::boxed::box_uninit_array_into_vec_unsafe(
+            $crate::intrinsics::write_box_via_move($crate::boxed::Box::new_uninit(), [$($x),+])
        )


Has an immediately invoked closure been considered?
(Though having an added closure for each occurance of vec! might have problems on its own. Is there a way to mark the closure inline(always) to prevent extra function calls when using a debug build?)

Suggested change

$crate::boxed::box_uninit_array_into_vec_unsafe(

$crate::intrinsics::write_box_via_move($crate::boxed::Box::new_uninit(), [$($x),+])

)

(|b| unsafe{

$crate::boxed::box_uninit_array_into_vec_unsafe(b)

})(

$crate::intrinsics::write_box_via_move(

$crate::boxed::Box::new_uninit(), [$($x),+]

)

)

Unfortunately, that does not work because $x might contain statements like return or break that won't work correctly inside the closure.

EDIT: Oh wait, the $x isn't even inside the closure. Yeah that could work, but given how perf-sensitive this is I'd rather not add a closure here.

And yes, #[inline(always)] works on closures.

bors · 2025-11-08T21:18:39Z

☔ The latest upstream changes (presumably #148691) made this pull request unmergeable. Please resolve the merge conflicts.

cjgillot

I'm going to wait with fixing Clippy until we agree we even want this change.

Thanks @RalfJung for the thorough investigation, much further than what I'd have done.

I'm generally in favor of this change, in particular because it simplifies MIR language.

However, this also introduces a lot of accidental complexity for perf reasons. I saw you did your best to reduce this complexity, so I won't bother you much on this.

View changes since this review

cjgillot · 2025-11-08T21:59:04Z

library/alloc/src/boxed.rs

+        // Nothing below can panic so we do not have to worry about deallocating `ptr`.
+        // SAFETY: we just allocated the box to store `x`.
+        unsafe { core::intrinsics::write_via_move(ptr, x) };
+        // SAFETY: we just initialized `b`.
+        unsafe { mem::transmute(ptr) }


Do you mean write_box_via_move? Is the "bit slower" acceptable to simplify the implementation?

cjgillot · 2025-11-08T22:02:36Z

library/alloc/src/boxed.rs

+        // Nothing below can panic so we do not have to worry about deallocating `ptr`.
+        // SAFETY: we just allocated the box to store `x`.
+        unsafe { core::intrinsics::write_via_move(ptr, x) };
+        // SAFETY: we just initialized `b`.
+        unsafe { mem::transmute(ptr) }


Should new_in and new_uninit_in get the same kind of inlined implementation?

cjgillot · 2025-11-08T23:34:39Z

tests/mir-opt/dont_reset_cast_kind_without_updating_operand.test.GVN.64bit.panic-abort.diff

This is a regression test for an ICE where GVN would cast with wrong types. We only check a cast, the rest is boilerplate from inlining.

cjgillot · 2025-11-09T00:03:52Z

compiler/rustc_mir_build/src/builder/expr/into.rs

+                                .into(),
+                                destination: inner_ptr,
+                                target: Some(success),
+                                unwind: UnwindAction::Continue,


box_uninit_as_mut_ptr cannot unwind, so UnwindAction::Unreachable should be even better.

requires lowering write_via_move during MIR building to make it just like an assignment

This allows us to get rid of box_new entirely

rustbot · 2025-11-09T11:02:29Z

This PR was rebased onto a different master commit. Here's a range-diff highlighting what actually changed.

Rebasing is a normal part of keeping PRs up to date, so no action is needed—this note is just to help reviewers.

rustbot · 2025-11-09T11:57:16Z

Some changes occurred in src/tools/clippy

cc @rust-lang/clippy

RalfJung · 2025-11-09T11:57:22Z

@rust-lang/clippy I need help dealing with the remaining clippy issues here.

A bunch of tests now say something about the vec! macro having an MSRV of 1.82.0. I couldn't figure out why the tests even check that, but the fundamental mistake here is to look inside a macro expansion and then check the MSRV you find there -- on older Rust, the macro expands differently, so it makes no sense to require the functions inside the vec! macro to have a low MSRV.
The logic for check_unwrap_or_default no longer kicks in for some of these cases. I think this is due to expr_type_is_certain no longer considering the type as "certain" in these examples, but I am not sure why that happens or what to do about that.

rust-log-analyzer · 2025-11-09T13:04:10Z

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

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

tests/ui/should_impl_trait/method_list_2.rs (revision `edition2015`) ... ok
tests/ui/should_impl_trait/method_list_2.rs (revision `edition2021`) ... ok

FAILED TEST: tests/ui/borrow_as_ptr.rs
command: CLIPPY_CONF_DIR="tests" RUSTC_ICE="0" "/checkout/obj/build/x86_64-unknown-linux-gnu/stage2-tools/x86_64-unknown-linux-gnu/release/clippy-driver" "--error-format=json" "--emit=metadata" "-Aunused" "-Ainternal_features" "-Zui-testing" "-Zdeduplicate-diagnostics=no" "-Dwarnings" "-Ldependency=/checkout/obj/build/x86_64-unknown-linux-gnu/stage2-tools/release/deps" "--sysroot=/checkout/obj/build/x86_64-unknown-linux-gnu/stage2" "--out-dir" "/checkout/obj/build/x86_64-unknown-linux-gnu/stage2-tools/ui_test/0/tests/ui" "tests/ui/borrow_as_ptr.rs" "--extern" "proc_macros=/checkout/obj/build/x86_64-unknown-linux-gnu/stage2-tools/ui_test/0/tests/ui/auxiliary/libproc_macros.so" "-L" "/checkout/obj/build/x86_64-unknown-linux-gnu/stage2-tools/ui_test/0/tests/ui/auxiliary" "--extern" "futures=/checkout/obj/build/x86_64-unknown-linux-gnu/stage2-tools/x86_64-unknown-linux-gnu/debug/deps/libfutures-a8bf6f69c9b80e37.rlib" "--extern" "futures=/checkout/obj/build/x86_64-unknown-linux-gnu/stage2-tools/x86_64-unknown-linux-gnu/debug/deps/libfutures-a8bf6f69c9b80e37.rmeta" "--extern" "itertools=/checkout/obj/build/x86_64-unknown-linux-gnu/stage2-tools/x86_64-unknown-linux-gnu/debug/deps/libitertools-2d82d3ce68d9c3ee.rlib" "--extern" "itertools=/checkout/obj/build/x86_64-unknown-linux-gnu/stage2-tools/x86_64-unknown-linux-gnu/debug/deps/libitertools-2d82d3ce68d9c3ee.rmeta" "--extern" "libc=/checkout/obj/build/x86_64-unknown-linux-gnu/stage2-tools/x86_64-unknown-linux-gnu/debug/deps/liblibc-e86cd1a7c22fc60c.rlib" "--extern" "libc=/checkout/obj/build/x86_64-unknown-linux-gnu/stage2-tools/x86_64-unknown-linux-gnu/debug/deps/liblibc-e86cd1a7c22fc60c.rmeta" "--extern" "parking_lot=/checkout/obj/build/x86_64-unknown-linux-gnu/stage2-tools/x86_64-unknown-linux-gnu/debug/deps/libparking_lot-a94abfa769f04e5d.rlib" "--extern" "parking_lot=/checkout/obj/build/x86_64-unknown-linux-gnu/stage2-tools/x86_64-unknown-linux-gnu/debug/deps/libparking_lot-a94abfa769f04e5d.rmeta" "--extern" "quote=/checkout/obj/build/x86_64-unknown-linux-gnu/stage2-tools/x86_64-unknown-linux-gnu/debug/deps/libquote-22b65b7753b00e23.rlib" "--extern" "quote=/checkout/obj/build/x86_64-unknown-linux-gnu/stage2-tools/x86_64-unknown-linux-gnu/debug/deps/libquote-22b65b7753b00e23.rmeta" "--extern" "regex=/checkout/obj/build/x86_64-unknown-linux-gnu/stage2-tools/x86_64-unknown-linux-gnu/debug/deps/libregex-4368476ea091f8ef.rlib" "--extern" "regex=/checkout/obj/build/x86_64-unknown-linux-gnu/stage2-tools/x86_64-unknown-linux-gnu/debug/deps/libregex-4368476ea091f8ef.rmeta" "--extern" "serde=/checkout/obj/build/x86_64-unknown-linux-gnu/stage2-tools/x86_64-unknown-linux-gnu/debug/deps/libserde-978a92b8a77cdf3d.rlib" "--extern" "serde=/checkout/obj/build/x86_64-unknown-linux-gnu/stage2-tools/x86_64-unknown-linux-gnu/debug/deps/libserde-978a92b8a77cdf3d.rmeta" "--extern" "syn=/checkout/obj/build/x86_64-unknown-linux-gnu/stage2-tools/x86_64-unknown-linux-gnu/debug/deps/libsyn-fdddf18d670fbd00.rlib" "--extern" "syn=/checkout/obj/build/x86_64-unknown-linux-gnu/stage2-tools/x86_64-unknown-linux-gnu/debug/deps/libsyn-fdddf18d670fbd00.rmeta" "--extern" "tokio=/checkout/obj/build/x86_64-unknown-linux-gnu/stage2-tools/x86_64-unknown-linux-gnu/debug/deps/libtokio-1fc6a815de90452d.rlib" "--extern" "tokio=/checkout/obj/build/x86_64-unknown-linux-gnu/stage2-tools/x86_64-unknown-linux-gnu/debug/deps/libtokio-1fc6a815de90452d.rmeta" "-L" "/checkout/obj/build/x86_64-unknown-linux-gnu/stage2-tools/debug/deps" "-L" "/checkout/obj/build/x86_64-unknown-linux-gnu/stage2-tools/x86_64-unknown-linux-gnu/debug/deps" "--edition" "2024"

error: actual output differed from expected
Execute `./x test src/tools/clippy --bless` to update `tests/ui/borrow_as_ptr.stderr` to the actual output
--- tests/ui/borrow_as_ptr.stderr
+++ <stderr output>
 error: borrow as raw pointer
   --> tests/ui/borrow_as_ptr.rs:14:14
... 5 lines skipped ...
    = help: to override `-D warnings` add `#[allow(clippy::borrow_as_ptr)]`
 
+error: current MSRV (Minimum Supported Rust Version) is `1.75.0` but this item is stable since `1.82.0`
+  --> tests/ui/borrow_as_ptr.rs:18:15
+   |
+LL |     let vec = vec![1];
+   |               ^^^^^^^
+   |
---
Full unnormalized output:
error: borrow as raw pointer
##[error]  --> tests/ui/borrow_as_ptr.rs:14:14
   |
LL |     let _p = &val as *const i32;
   |              ^^^^^^^^^^^^^^^^^^ help: try: `std::ptr::addr_of!(val)`
   |
   = note: `-D clippy::borrow-as-ptr` implied by `-D warnings`
   = help: to override `-D warnings` add `#[allow(clippy::borrow_as_ptr)]`

error: current MSRV (Minimum Supported Rust Version) is `1.75.0` but this item is stable since `1.82.0`
##[error]  --> tests/ui/borrow_as_ptr.rs:18:15
   |
LL |     let vec = vec![1];
   |               ^^^^^^^
   |
   = note: `-D clippy::incompatible-msrv` implied by `-D warnings`
   = help: to override `-D warnings` add `#[allow(clippy::incompatible_msrv)]`
   = note: this error originates in the macro `vec` (in Nightly builds, run with -Z macro-backtrace for more info)

error: borrow as raw pointer
##[error]  --> tests/ui/borrow_as_ptr.rs:22:18
   |
LL |     let _p_mut = &mut val_mut as *mut i32;
   |                  ^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `std::ptr::addr_of_mut!(val_mut)`

error: borrow as raw pointer
##[error]  --> tests/ui/borrow_as_ptr.rs:26:16
   |
LL |     let _raw = (&mut x[1] as *mut i32).wrapping_offset(-1);
   |                ^^^^^^^^^^^^^^^^^^^^^^^ help: try: `std::ptr::addr_of_mut!(x[1])`

error: borrow as raw pointer
##[error]  --> tests/ui/borrow_as_ptr.rs:32:17
   |
LL |     let _raw = (&mut x[1] as *mut i32).wrapping_offset(-1);
   |                 ^^^^^^^^^^^^^^^^^^^^^ help: try: `&raw mut x[1]`

error: implicit borrow as raw pointer
##[error]  --> tests/ui/borrow_as_ptr.rs:38:25
   |
LL |     let p: *const i32 = &val;
   |                         ^^^^
   |
help: use a raw pointer instead
   |
LL |     let p: *const i32 = &raw const val;
   |                          +++++++++

error: implicit borrow as raw pointer
##[error]  --> tests/ui/borrow_as_ptr.rs:42:23
   |
---

error: implicit borrow as raw pointer
##[error]  --> tests/ui/borrow_as_ptr.rs:47:19
   |
LL |     core::ptr::eq(&val, &1);
   |                   ^^^^
   |
help: use a raw pointer instead
   |
LL |     core::ptr::eq(&raw const val, &1);
   |                    +++++++++

error: aborting due to 8 previous errors



error: there were 1 unmatched diagnostics
##[error]  --> tests/ui/borrow_as_ptr.rs:18:15
   |
18 |     let vec = vec![1];
   |               ^^^^^^^ Error[clippy::incompatible_msrv]: current MSRV (Minimum Supported Rust Version) is `1.75.0` but this item is stable since `1.82.0`
   |

full stderr:
error: borrow as raw pointer
##[error]  --> tests/ui/borrow_as_ptr.rs:14:14
   |
LL |     let _p = &val as *const i32;
   |              ^^^^^^^^^^^^^^^^^^ help: try: `std::ptr::addr_of!(val)`
   |
   = note: `-D clippy::borrow-as-ptr` implied by `-D warnings`
   = help: to override `-D warnings` add `#[allow(clippy::borrow_as_ptr)]`

error: current MSRV (Minimum Supported Rust Version) is `1.75.0` but this item is stable since `1.82.0`
##[error]  --> tests/ui/borrow_as_ptr.rs:18:15
   |
LL |     let vec = vec![1];
   |               ^^^^^^^
   |
   = note: `-D clippy::incompatible-msrv` implied by `-D warnings`
   = help: to override `-D warnings` add `#[allow(clippy::incompatible_msrv)]`
   = note: this error originates in the macro `vec` (in Nightly builds, run with -Z macro-backtrace for more info)

error: borrow as raw pointer
##[error]  --> tests/ui/borrow_as_ptr.rs:22:18
   |
LL |     let _p_mut = &mut val_mut as *mut i32;
   |                  ^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `std::ptr::addr_of_mut!(val_mut)`

error: borrow as raw pointer
##[error]  --> tests/ui/borrow_as_ptr.rs:26:16
   |
LL |     let _raw = (&mut x[1] as *mut i32).wrapping_offset(-1);
   |                ^^^^^^^^^^^^^^^^^^^^^^^ help: try: `std::ptr::addr_of_mut!(x[1])`

error: borrow as raw pointer
##[error]  --> tests/ui/borrow_as_ptr.rs:32:17
   |
LL |     let _raw = (&mut x[1] as *mut i32).wrapping_offset(-1);
   |                 ^^^^^^^^^^^^^^^^^^^^^ help: try: `&raw mut x[1]`

error: implicit borrow as raw pointer
##[error]  --> tests/ui/borrow_as_ptr.rs:38:25
   |
LL |     let p: *const i32 = &val;
   |                         ^^^^
   |
help: use a raw pointer instead
   |
LL |     let p: *const i32 = &raw const val;
   |                          +++++++++

error: implicit borrow as raw pointer
##[error]  --> tests/ui/borrow_as_ptr.rs:42:23
   |
---

error: implicit borrow as raw pointer
##[error]  --> tests/ui/borrow_as_ptr.rs:47:19
   |
LL |     core::ptr::eq(&val, &1);
   |                   ^^^^
   |
help: use a raw pointer instead
   |
LL |     core::ptr::eq(&raw const val, &1);
   |                    +++++++++

error: aborting due to 8 previous errors


full stdout:



FAILED TEST: tests/ui/methods_fixable.rs
command: CLIPPY_CONF_DIR="tests" RUSTC_ICE="0" "/checkout/obj/build/x86_64-unknown-linux-gnu/stage2-tools/x86_64-unknown-linux-gnu/release/clippy-driver" "--error-format=json" "--emit=metadata" "-Aunused" "-Ainternal_features" "-Zui-testing" "-Zdeduplicate-diagnostics=no" "-Dwarnings" "-Ldependency=/checkout/obj/build/x86_64-unknown-linux-gnu/stage2-tools/release/deps" "--sysroot=/checkout/obj/build/x86_64-unknown-linux-gnu/stage2" "--out-dir" "/checkout/obj/build/x86_64-unknown-linux-gnu/stage2-tools/ui_test/0/tests/ui" "tests/ui/methods_fixable.rs" "--extern" "futures=/checkout/obj/build/x86_64-unknown-linux-gnu/stage2-tools/x86_64-unknown-linux-gnu/debug/deps/libfutures-a8bf6f69c9b80e37.rlib" "--extern" "futures=/checkout/obj/build/x86_64-unknown-linux-gnu/stage2-tools/x86_64-unknown-linux-gnu/debug/deps/libfutures-a8bf6f69c9b80e37.rmeta" "--extern" "itertools=/checkout/obj/build/x86_64-unknown-linux-gnu/stage2-tools/x86_64-unknown-linux-gnu/debug/deps/libitertools-2d82d3ce68d9c3ee.rlib" "--extern" "itertools=/checkout/obj/build/x86_64-unknown-linux-gnu/stage2-tools/x86_64-unknown-linux-gnu/debug/deps/libitertools-2d82d3ce68d9c3ee.rmeta" "--extern" "libc=/checkout/obj/build/x86_64-unknown-linux-gnu/stage2-tools/x86_64-unknown-linux-gnu/debug/deps/liblibc-e86cd1a7c22fc60c.rlib" "--extern" "libc=/checkout/obj/build/x86_64-unknown-linux-gnu/stage2-tools/x86_64-unknown-linux-gnu/debug/deps/liblibc-e86cd1a7c22fc60c.rmeta" "--extern" "parking_lot=/checkout/obj/build/x86_64-unknown-linux-gnu/stage2-tools/x86_64-unknown-linux-gnu/debug/deps/libparking_lot-a94abfa769f04e5d.rlib" "--extern" "parking_lot=/checkout/obj/build/x86_64-unknown-linux-gnu/stage2-tools/x86_64-unknown-linux-gnu/debug/deps/libparking_lot-a94abfa769f04e5d.rmeta" "--extern" "quote=/checkout/obj/build/x86_64-unknown-linux-gnu/stage2-tools/x86_64-unknown-linux-gnu/debug/deps/libquote-22b65b7753b00e23.rlib" "--extern" "quote=/checkout/obj/build/x86_64-unknown-linux-gnu/stage2-tools/x86_64-unknown-linux-gnu/debug/deps/libquote-22b65b7753b00e23.rmeta" "--extern" "regex=/checkout/obj/build/x86_64-unknown-linux-gnu/stage2-tools/x86_64-unknown-linux-gnu/debug/deps/libregex-4368476ea091f8ef.rlib" "--extern" "regex=/checkout/obj/build/x86_64-unknown-linux-gnu/stage2-tools/x86_64-unknown-linux-gnu/debug/deps/libregex-4368476ea091f8ef.rmeta" "--extern" "serde=/checkout/obj/build/x86_64-unknown-linux-gnu/stage2-tools/x86_64-unknown-linux-gnu/debug/deps/libserde-978a92b8a77cdf3d.rlib" "--extern" "serde=/checkout/obj/build/x86_64-unknown-linux-gnu/stage2-tools/x86_64-unknown-linux-gnu/debug/deps/libserde-978a92b8a77cdf3d.rmeta" "--extern" "syn=/checkout/obj/build/x86_64-unknown-linux-gnu/stage2-tools/x86_64-unknown-linux-gnu/debug/deps/libsyn-fdddf18d670fbd00.rlib" "--extern" "syn=/checkout/obj/build/x86_64-unknown-linux-gnu/stage2-tools/x86_64-unknown-linux-gnu/debug/deps/libsyn-fdddf18d670fbd00.rmeta" "--extern" "tokio=/checkout/obj/build/x86_64-unknown-linux-gnu/stage2-tools/x86_64-unknown-linux-gnu/debug/deps/libtokio-1fc6a815de90452d.rlib" "--extern" "tokio=/checkout/obj/build/x86_64-unknown-linux-gnu/stage2-tools/x86_64-unknown-linux-gnu/debug/deps/libtokio-1fc6a815de90452d.rmeta" "-L" "/checkout/obj/build/x86_64-unknown-linux-gnu/stage2-tools/debug/deps" "-L" "/checkout/obj/build/x86_64-unknown-linux-gnu/stage2-tools/x86_64-unknown-linux-gnu/debug/deps" "--edition" "2024"

error: actual output differed from expected
Execute `./x test src/tools/clippy --bless` to update `tests/ui/methods_fixable.stderr` to the actual output
--- tests/ui/methods_fixable.stderr
+++ <stderr output>
 error: called `filter(..).next()` on an `Iterator`. This is more succinctly expressed by calling `.find(..)` instead
   --> tests/ui/methods_fixable.rs:9:13
... 17 lines skipped ...
    |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `vec![1].into_iter().rfind(|&x| x < 0)`
 
-error: aborting due to 3 previous errors
+error: current MSRV (Minimum Supported Rust Version) is `1.27.0` but this item is stable since `1.36.0`
+  --> tests/ui/methods_fixable.rs:18:13
+   |
+LL |     let _ = vec![1].into_iter().filter(|&x| x < 0).next_back();
+   |             ^^^^^^^
+   |
+   = note: `-D clippy::incompatible-msrv` implied by `-D warnings`
+   = help: to override `-D warnings` add `#[allow(clippy::incompatible_msrv)]`
+   = note: this error originates in the macro `vec` (in Nightly builds, run with -Z macro-backtrace for more info)
 
+error: current MSRV (Minimum Supported Rust Version) is `1.27.0` but this item is stable since `1.82.0`
+  --> tests/ui/methods_fixable.rs:18:13
+   |
+LL |     let _ = vec![1].into_iter().filter(|&x| x < 0).next_back();
+   |             ^^^^^^^
+   |
+   = note: this error originates in the macro `vec` (in Nightly builds, run with -Z macro-backtrace for more info)
+
+error: current MSRV (Minimum Supported Rust Version) is `1.26.0` but this item is stable since `1.36.0`
+  --> tests/ui/methods_fixable.rs:24:13
+   |
+LL |     let _ = vec![1].into_iter().filter(|&x| x < 0).next_back();
+   |             ^^^^^^^
+   |
+   = note: this error originates in the macro `vec` (in Nightly builds, run with -Z macro-backtrace for more info)
+
+error: current MSRV (Minimum Supported Rust Version) is `1.26.0` but this item is stable since `1.82.0`
+  --> tests/ui/methods_fixable.rs:24:13
+   |
+LL |     let _ = vec![1].into_iter().filter(|&x| x < 0).next_back();
+   |             ^^^^^^^
+   |
+   = note: this error originates in the macro `vec` (in Nightly builds, run with -Z macro-backtrace for more info)
+
+error: aborting due to 7 previous errors
+

Full unnormalized output:
error: called `filter(..).next()` on an `Iterator`. This is more succinctly expressed by calling `.find(..)` instead
##[error]  --> tests/ui/methods_fixable.rs:9:13
   |
LL |     let _ = v.iter().filter(|&x| *x < 0).next();
   |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `v.iter().find(|&x| *x < 0)`
   |
   = note: `-D clippy::filter-next` implied by `-D warnings`
   = help: to override `-D warnings` add `#[allow(clippy::filter_next)]`

error: called `filter(..).next_back()` on an `DoubleEndedIterator`. This is more succinctly expressed by calling `.rfind(..)` instead
##[error]  --> tests/ui/methods_fixable.rs:12:13
   |
LL |     let _ = v.iter().filter(|&x| *x < 0).next_back();
   |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `v.iter().rfind(|&x| *x < 0)`

error: called `filter(..).next_back()` on an `DoubleEndedIterator`. This is more succinctly expressed by calling `.rfind(..)` instead
##[error]  --> tests/ui/methods_fixable.rs:18:13
   |
LL |     let _ = vec![1].into_iter().filter(|&x| x < 0).next_back();
   |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `vec![1].into_iter().rfind(|&x| x < 0)`

error: current MSRV (Minimum Supported Rust Version) is `1.27.0` but this item is stable since `1.36.0`
##[error]  --> tests/ui/methods_fixable.rs:18:13
   |
LL |     let _ = vec![1].into_iter().filter(|&x| x < 0).next_back();
   |             ^^^^^^^
   |
   = note: `-D clippy::incompatible-msrv` implied by `-D warnings`
   = help: to override `-D warnings` add `#[allow(clippy::incompatible_msrv)]`
   = note: this error originates in the macro `vec` (in Nightly builds, run with -Z macro-backtrace for more info)

error: current MSRV (Minimum Supported Rust Version) is `1.27.0` but this item is stable since `1.82.0`
##[error]  --> tests/ui/methods_fixable.rs:18:13
   |
LL |     let _ = vec![1].into_iter().filter(|&x| x < 0).next_back();
   |             ^^^^^^^
   |
   = note: this error originates in the macro `vec` (in Nightly builds, run with -Z macro-backtrace for more info)

error: current MSRV (Minimum Supported Rust Version) is `1.26.0` but this item is stable since `1.36.0`
##[error]  --> tests/ui/methods_fixable.rs:24:13
   |
LL |     let _ = vec![1].into_iter().filter(|&x| x < 0).next_back();
   |             ^^^^^^^
   |
   = note: this error originates in the macro `vec` (in Nightly builds, run with -Z macro-backtrace for more info)

error: current MSRV (Minimum Supported Rust Version) is `1.26.0` but this item is stable since `1.82.0`
##[error]  --> tests/ui/methods_fixable.rs:24:13
   |
LL |     let _ = vec![1].into_iter().filter(|&x| x < 0).next_back();
   |             ^^^^^^^
   |
   = note: this error originates in the macro `vec` (in Nightly builds, run with -Z macro-backtrace for more info)

error: aborting due to 7 previous errors



error: there were 2 unmatched diagnostics
##[error]  --> tests/ui/methods_fixable.rs:18:13
   |
18 |     let _ = vec![1].into_iter().filter(|&x| x < 0).next_back();
   |             ^^^^^^^
   |             |
   |             Error[clippy::incompatible_msrv]: current MSRV (Minimum Supported Rust Version) is `1.27.0` but this item is stable since `1.36.0`
   |             Error[clippy::incompatible_msrv]: current MSRV (Minimum Supported Rust Version) is `1.27.0` but this item is stable since `1.82.0`
   |

error: there were 2 unmatched diagnostics
##[error]  --> tests/ui/methods_fixable.rs:24:13
   |
24 |     let _ = vec![1].into_iter().filter(|&x| x < 0).next_back();
   |             ^^^^^^^
   |             |
   |             Error[clippy::incompatible_msrv]: current MSRV (Minimum Supported Rust Version) is `1.26.0` but this item is stable since `1.36.0`
   |             Error[clippy::incompatible_msrv]: current MSRV (Minimum Supported Rust Version) is `1.26.0` but this item is stable since `1.82.0`
   |

full stderr:
error: called `filter(..).next()` on an `Iterator`. This is more succinctly expressed by calling `.find(..)` instead
##[error]  --> tests/ui/methods_fixable.rs:9:13
   |
LL |     let _ = v.iter().filter(|&x| *x < 0).next();
   |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `v.iter().find(|&x| *x < 0)`
   |
   = note: `-D clippy::filter-next` implied by `-D warnings`
   = help: to override `-D warnings` add `#[allow(clippy::filter_next)]`

error: called `filter(..).next_back()` on an `DoubleEndedIterator`. This is more succinctly expressed by calling `.rfind(..)` instead
##[error]  --> tests/ui/methods_fixable.rs:12:13
   |
LL |     let _ = v.iter().filter(|&x| *x < 0).next_back();
   |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `v.iter().rfind(|&x| *x < 0)`

error: called `filter(..).next_back()` on an `DoubleEndedIterator`. This is more succinctly expressed by calling `.rfind(..)` instead
##[error]  --> tests/ui/methods_fixable.rs:18:13
   |
LL |     let _ = vec![1].into_iter().filter(|&x| x < 0).next_back();
   |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `vec![1].into_iter().rfind(|&x| x < 0)`

error: current MSRV (Minimum Supported Rust Version) is `1.27.0` but this item is stable since `1.36.0`
##[error]  --> tests/ui/methods_fixable.rs:18:13
   |
LL |     let _ = vec![1].into_iter().filter(|&x| x < 0).next_back();
   |             ^^^^^^^
   |
   = note: `-D clippy::incompatible-msrv` implied by `-D warnings`
   = help: to override `-D warnings` add `#[allow(clippy::incompatible_msrv)]`
   = note: this error originates in the macro `vec` (in Nightly builds, run with -Z macro-backtrace for more info)

error: current MSRV (Minimum Supported Rust Version) is `1.27.0` but this item is stable since `1.82.0`
##[error]  --> tests/ui/methods_fixable.rs:18:13
   |
LL |     let _ = vec![1].into_iter().filter(|&x| x < 0).next_back();
   |             ^^^^^^^
   |
   = note: this error originates in the macro `vec` (in Nightly builds, run with -Z macro-backtrace for more info)

error: current MSRV (Minimum Supported Rust Version) is `1.26.0` but this item is stable since `1.36.0`
##[error]  --> tests/ui/methods_fixable.rs:24:13
   |
LL |     let _ = vec![1].into_iter().filter(|&x| x < 0).next_back();
   |             ^^^^^^^
   |
   = note: this error originates in the macro `vec` (in Nightly builds, run with -Z macro-backtrace for more info)

error: current MSRV (Minimum Supported Rust Version) is `1.26.0` but this item is stable since `1.82.0`
##[error]  --> tests/ui/methods_fixable.rs:24:13
   |
LL |     let _ = vec![1].into_iter().filter(|&x| x < 0).next_back();
   |             ^^^^^^^
   |
   = note: this error originates in the macro `vec` (in Nightly builds, run with -Z macro-backtrace for more info)

error: aborting due to 7 previous errors


full stdout:



FAILED TEST: tests/ui/vec.rs
command: CLIPPY_CONF_DIR="tests" RUSTC_ICE="0" "/checkout/obj/build/x86_64-unknown-linux-gnu/stage2-tools/x86_64-unknown-linux-gnu/release/clippy-driver" "--error-format=json" "--emit=metadata" "-Aunused" "-Ainternal_features" "-Zui-testing" "-Zdeduplicate-diagnostics=no" "-Dwarnings" "-Ldependency=/checkout/obj/build/x86_64-unknown-linux-gnu/stage2-tools/release/deps" "--sysroot=/checkout/obj/build/x86_64-unknown-linux-gnu/stage2" "--out-dir" "/checkout/obj/build/x86_64-unknown-linux-gnu/stage2-tools/ui_test/0/tests/ui" "tests/ui/vec.rs" "--extern" "futures=/checkout/obj/build/x86_64-unknown-linux-gnu/stage2-tools/x86_64-unknown-linux-gnu/debug/deps/libfutures-a8bf6f69c9b80e37.rlib" "--extern" "futures=/checkout/obj/build/x86_64-unknown-linux-gnu/stage2-tools/x86_64-unknown-linux-gnu/debug/deps/libfutures-a8bf6f69c9b80e37.rmeta" "--extern" "itertools=/checkout/obj/build/x86_64-unknown-linux-gnu/stage2-tools/x86_64-unknown-linux-gnu/debug/deps/libitertools-2d82d3ce68d9c3ee.rlib" "--extern" "itertools=/checkout/obj/build/x86_64-unknown-linux-gnu/stage2-tools/x86_64-unknown-linux-gnu/debug/deps/libitertools-2d82d3ce68d9c3ee.rmeta" "--extern" "libc=/checkout/obj/build/x86_64-unknown-linux-gnu/stage2-tools/x86_64-unknown-linux-gnu/debug/deps/liblibc-e86cd1a7c22fc60c.rlib" "--extern" "libc=/checkout/obj/build/x86_64-unknown-linux-gnu/stage2-tools/x86_64-unknown-linux-gnu/debug/deps/liblibc-e86cd1a7c22fc60c.rmeta" "--extern" "parking_lot=/checkout/obj/build/x86_64-unknown-linux-gnu/stage2-tools/x86_64-unknown-linux-gnu/debug/deps/libparking_lot-a94abfa769f04e5d.rlib" "--extern" "parking_lot=/checkout/obj/build/x86_64-unknown-linux-gnu/stage2-tools/x86_64-unknown-linux-gnu/debug/deps/libparking_lot-a94abfa769f04e5d.rmeta" "--extern" "quote=/checkout/obj/build/x86_64-unknown-linux-gnu/stage2-tools/x86_64-unknown-linux-gnu/debug/deps/libquote-22b65b7753b00e23.rlib" "--extern" "quote=/checkout/obj/build/x86_64-unknown-linux-gnu/stage2-tools/x86_64-unknown-linux-gnu/debug/deps/libquote-22b65b7753b00e23.rmeta" "--extern" "regex=/checkout/obj/build/x86_64-unknown-linux-gnu/stage2-tools/x86_64-unknown-linux-gnu/debug/deps/libregex-4368476ea091f8ef.rlib" "--extern" "regex=/checkout/obj/build/x86_64-unknown-linux-gnu/stage2-tools/x86_64-unknown-linux-gnu/debug/deps/libregex-4368476ea091f8ef.rmeta" "--extern" "serde=/checkout/obj/build/x86_64-unknown-linux-gnu/stage2-tools/x86_64-unknown-linux-gnu/debug/deps/libserde-978a92b8a77cdf3d.rlib" "--extern" "serde=/checkout/obj/build/x86_64-unknown-linux-gnu/stage2-tools/x86_64-unknown-linux-gnu/debug/deps/libserde-978a92b8a77cdf3d.rmeta" "--extern" "syn=/checkout/obj/build/x86_64-unknown-linux-gnu/stage2-tools/x86_64-unknown-linux-gnu/debug/deps/libsyn-fdddf18d670fbd00.rlib" "--extern" "syn=/checkout/obj/build/x86_64-unknown-linux-gnu/stage2-tools/x86_64-unknown-linux-gnu/debug/deps/libsyn-fdddf18d670fbd00.rmeta" "--extern" "tokio=/checkout/obj/build/x86_64-unknown-linux-gnu/stage2-tools/x86_64-unknown-linux-gnu/debug/deps/libtokio-1fc6a815de90452d.rlib" "--extern" "tokio=/checkout/obj/build/x86_64-unknown-linux-gnu/stage2-tools/x86_64-unknown-linux-gnu/debug/deps/libtokio-1fc6a815de90452d.rmeta" "-L" "/checkout/obj/build/x86_64-unknown-linux-gnu/stage2-tools/debug/deps" "-L" "/checkout/obj/build/x86_64-unknown-linux-gnu/stage2-tools/x86_64-unknown-linux-gnu/debug/deps" "--edition" "2024"

error: actual output differed from expected
Execute `./x test src/tools/clippy --bless` to update `tests/ui/vec.stderr` to the actual output
--- tests/ui/vec.stderr
+++ <stderr output>
+error: current MSRV (Minimum Supported Rust Version) is `1.53.0` but this item is stable since `1.82.0`
+  --> tests/ui/vec.rs:177:14
+   |
+LL |     for a in vec![1, 2, 3] {
+   |              ^^^^^^^^^^^^^
+   |
+   = note: `-D clippy::incompatible-msrv` implied by `-D warnings`
+   = help: to override `-D warnings` add `#[allow(clippy::incompatible_msrv)]`
+   = note: this error originates in the macro `vec` (in Nightly builds, run with -Z macro-backtrace for more info)
+
+error: current MSRV (Minimum Supported Rust Version) is `1.53.0` but this item is stable since `1.82.0`
+  --> tests/ui/vec.rs:182:14
+   |
+LL |     for a in vec![String::new(), String::new()] {
+   |              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |
+   = note: this error originates in the macro `vec` (in Nightly builds, run with -Z macro-backtrace for more info)
+
+error: current MSRV (Minimum Supported Rust Version) is `1.52.0` but this item is stable since `1.82.0`
+  --> tests/ui/vec.rs:190:14
+   |
+LL |     for a in vec![1, 2, 3] {
+   |              ^^^^^^^^^^^^^
+   |
+   = note: this error originates in the macro `vec` (in Nightly builds, run with -Z macro-backtrace for more info)
+
+error: current MSRV (Minimum Supported Rust Version) is `1.52.0` but this item is stable since `1.82.0`
+  --> tests/ui/vec.rs:194:14
+   |
+LL |     for a in vec![String::new(), String::new()] {
+   |              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |
+   = note: this error originates in the macro `vec` (in Nightly builds, run with -Z macro-backtrace for more info)
+
 error: useless use of `vec!`
---
-error: aborting due to 22 previous errors
+error: aborting due to 26 previous errors
 

Full unnormalized output:
error: current MSRV (Minimum Supported Rust Version) is `1.53.0` but this item is stable since `1.82.0`
##[error]  --> tests/ui/vec.rs:177:14
   |
LL |     for a in vec![1, 2, 3] {
   |              ^^^^^^^^^^^^^
   |
   = note: `-D clippy::incompatible-msrv` implied by `-D warnings`
   = help: to override `-D warnings` add `#[allow(clippy::incompatible_msrv)]`
   = note: this error originates in the macro `vec` (in Nightly builds, run with -Z macro-backtrace for more info)

error: current MSRV (Minimum Supported Rust Version) is `1.53.0` but this item is stable since `1.82.0`
##[error]  --> tests/ui/vec.rs:182:14
   |
LL |     for a in vec![String::new(), String::new()] {
   |              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
   |
   = note: this error originates in the macro `vec` (in Nightly builds, run with -Z macro-backtrace for more info)

error: current MSRV (Minimum Supported Rust Version) is `1.52.0` but this item is stable since `1.82.0`
##[error]  --> tests/ui/vec.rs:190:14
   |
LL |     for a in vec![1, 2, 3] {
   |              ^^^^^^^^^^^^^
   |
   = note: this error originates in the macro `vec` (in Nightly builds, run with -Z macro-backtrace for more info)

error: current MSRV (Minimum Supported Rust Version) is `1.52.0` but this item is stable since `1.82.0`
##[error]  --> tests/ui/vec.rs:194:14
   |
LL |     for a in vec![String::new(), String::new()] {
   |              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
   |
   = note: this error originates in the macro `vec` (in Nightly builds, run with -Z macro-backtrace for more info)

error: useless use of `vec!`
##[error]  --> tests/ui/vec.rs:30:14
   |
LL |     on_slice(&vec![]);
   |              ^^^^^^^ help: you can use a slice directly: `&[]`
   |
   = note: `-D clippy::useless-vec` implied by `-D warnings`
   = help: to override `-D warnings` add `#[allow(clippy::useless_vec)]`

error: useless use of `vec!`
---

error: useless use of `vec!`
##[error]  --> tests/ui/vec.rs:36:14
   |
LL |     on_slice(&vec![1, 2]);
   |              ^^^^^^^^^^^ help: you can use a slice directly: `&[1, 2]`

error: useless use of `vec!`
##[error]  --> tests/ui/vec.rs:39:18
   |
LL |     on_mut_slice(&mut vec![1, 2]);
   |                  ^^^^^^^^^^^^^^^ help: you can use a slice directly: `&mut [1, 2]`

error: useless use of `vec!`
##[error]  --> tests/ui/vec.rs:42:14
   |
LL |     on_slice(&vec![1, 2]);
   |              ^^^^^^^^^^^ help: you can use a slice directly: `&[1, 2]`

error: useless use of `vec!`
##[error]  --> tests/ui/vec.rs:45:18
   |
LL |     on_mut_slice(&mut vec![1, 2]);
   |                  ^^^^^^^^^^^^^^^ help: you can use a slice directly: `&mut [1, 2]`

error: useless use of `vec!`
##[error]  --> tests/ui/vec.rs:48:14
   |
LL |     on_slice(&vec!(1, 2));
   |              ^^^^^^^^^^^ help: you can use a slice directly: `&[1, 2]`

error: useless use of `vec!`
##[error]  --> tests/ui/vec.rs:51:18
   |
LL |     on_mut_slice(&mut vec![1, 2]);
   |                  ^^^^^^^^^^^^^^^ help: you can use a slice directly: `&mut [1, 2]`

error: useless use of `vec!`
##[error]  --> tests/ui/vec.rs:54:14
   |
LL |     on_slice(&vec![1; 2]);
   |              ^^^^^^^^^^^ help: you can use a slice directly: `&[1; 2]`

error: useless use of `vec!`
##[error]  --> tests/ui/vec.rs:57:18
   |
LL |     on_mut_slice(&mut vec![1; 2]);
   |                  ^^^^^^^^^^^^^^^ help: you can use a slice directly: `&mut [1; 2]`

error: useless use of `vec!`
##[error]  --> tests/ui/vec.rs:84:19
   |
LL |     let _x: i32 = vec![1, 2, 3].iter().sum();
   |                   ^^^^^^^^^^^^^ help: you can use an array directly: `[1, 2, 3]`

error: useless use of `vec!`
##[error]  --> tests/ui/vec.rs:88:17
   |
LL |     let mut x = vec![1, 2, 3];
   |                 ^^^^^^^^^^^^^ help: you can use an array directly: `[1, 2, 3]`

error: useless use of `vec!`
##[error]  --> tests/ui/vec.rs:95:22
   |
LL |     let _x: &[i32] = &vec![1, 2, 3];
   |                      ^^^^^^^^^^^^^^ help: you can use a slice directly: `&[1, 2, 3]`

error: useless use of `vec!`
##[error]  --> tests/ui/vec.rs:98:14
   |
LL |     for _ in vec![1, 2, 3] {}
   |              ^^^^^^^^^^^^^ help: you can use an array directly: `[1, 2, 3]`

error: useless use of `vec!`
##[error]  --> tests/ui/vec.rs:138:20
   |
LL |     for _string in vec![repro!(true), repro!(null)] {
   |                    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: you can use an array directly: `[repro!(true), repro!(null)]`

error: useless use of `vec!`
##[error]  --> tests/ui/vec.rs:156:18
   |
LL |     in_macro!(1, vec![1, 2], vec![1; 2]);
   |                  ^^^^^^^^^^ help: you can use an array directly: `[1, 2]`

error: useless use of `vec!`
##[error]  --> tests/ui/vec.rs:156:30
   |
LL |     in_macro!(1, vec![1, 2], vec![1; 2]);
   |                              ^^^^^^^^^^ help: you can use an array directly: `[1; 2]`

error: useless use of `vec!`
##[error]  --> tests/ui/vec.rs:177:14
   |
LL |     for a in vec![1, 2, 3] {
   |              ^^^^^^^^^^^^^ help: you can use an array directly: `[1, 2, 3]`

error: useless use of `vec!`
##[error]  --> tests/ui/vec.rs:182:14
   |
LL |     for a in vec![String::new(), String::new()] {
   |              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: you can use an array directly: `[String::new(), String::new()]`

error: useless use of `vec!`
##[error]  --> tests/ui/vec.rs:215:33
   |
LL |     this_macro_doesnt_need_vec!(vec![1]);
   |                                 ^^^^^^^ help: you can use an array directly: `[1]`

error: useless use of `vec!`
##[error]  --> tests/ui/vec.rs:242:14
   |
LL |     for a in &(vec![1, 2]) {}
   |              ^^^^^^^^^^^^^ help: you can use a slice directly: `&[1, 2]`

error: useless use of `vec!`
##[error]  --> tests/ui/vec.rs:250:13
   |
LL |     let v = &vec![];
   |             ^^^^^^^ help: you can use a slice directly: `&[]`

error: aborting due to 26 previous errors



error: there were 1 unmatched diagnostics
##[error]   --> tests/ui/vec.rs:177:14
    |
177 |     for a in vec![1, 2, 3] {
    |              ^^^^^^^^^^^^^ Error[clippy::incompatible_msrv]: current MSRV (Minimum Supported Rust Version) is `1.53.0` but this item is stable since `1.82.0`
    |

error: there were 1 unmatched diagnostics
##[error]   --> tests/ui/vec.rs:182:14
    |
182 |     for a in vec![String::new(), String::new()] {
    |              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ Error[clippy::incompatible_msrv]: current MSRV (Minimum Supported Rust Version) is `1.53.0` but this item is stable since `1.82.0`
    |

error: there were 1 unmatched diagnostics
##[error]   --> tests/ui/vec.rs:190:14
    |
190 |     for a in vec![1, 2, 3] {
    |              ^^^^^^^^^^^^^ Error[clippy::incompatible_msrv]: current MSRV (Minimum Supported Rust Version) is `1.52.0` but this item is stable since `1.82.0`
    |

error: there were 1 unmatched diagnostics
##[error]   --> tests/ui/vec.rs:194:14
    |
194 |     for a in vec![String::new(), String::new()] {
    |              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ Error[clippy::incompatible_msrv]: current MSRV (Minimum Supported Rust Version) is `1.52.0` but this item is stable since `1.82.0`
    |

full stderr:
error: current MSRV (Minimum Supported Rust Version) is `1.53.0` but this item is stable since `1.82.0`
##[error]  --> tests/ui/vec.rs:177:14
   |
LL |     for a in vec![1, 2, 3] {
   |              ^^^^^^^^^^^^^
   |
   = note: `-D clippy::incompatible-msrv` implied by `-D warnings`
   = help: to override `-D warnings` add `#[allow(clippy::incompatible_msrv)]`
   = note: this error originates in the macro `vec` (in Nightly builds, run with -Z macro-backtrace for more info)

error: current MSRV (Minimum Supported Rust Version) is `1.53.0` but this item is stable since `1.82.0`
##[error]  --> tests/ui/vec.rs:182:14
   |
LL |     for a in vec![String::new(), String::new()] {
   |              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
   |
   = note: this error originates in the macro `vec` (in Nightly builds, run with -Z macro-backtrace for more info)

error: current MSRV (Minimum Supported Rust Version) is `1.52.0` but this item is stable since `1.82.0`
##[error]  --> tests/ui/vec.rs:190:14
   |
LL |     for a in vec![1, 2, 3] {
   |              ^^^^^^^^^^^^^
   |
   = note: this error originates in the macro `vec` (in Nightly builds, run with -Z macro-backtrace for more info)

error: current MSRV (Minimum Supported Rust Version) is `1.52.0` but this item is stable since `1.82.0`
##[error]  --> tests/ui/vec.rs:194:14
   |
LL |     for a in vec![String::new(), String::new()] {
   |              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
   |
   = note: this error originates in the macro `vec` (in Nightly builds, run with -Z macro-backtrace for more info)

error: useless use of `vec!`
##[error]  --> tests/ui/vec.rs:30:14
   |
LL |     on_slice(&vec![]);
   |              ^^^^^^^ help: you can use a slice directly: `&[]`
   |
   = note: `-D clippy::useless-vec` implied by `-D warnings`
   = help: to override `-D warnings` add `#[allow(clippy::useless_vec)]`

error: useless use of `vec!`
---

error: useless use of `vec!`
##[error]  --> tests/ui/vec.rs:36:14
   |
LL |     on_slice(&vec![1, 2]);
   |              ^^^^^^^^^^^ help: you can use a slice directly: `&[1, 2]`

error: useless use of `vec!`
##[error]  --> tests/ui/vec.rs:39:18
   |
LL |     on_mut_slice(&mut vec![1, 2]);
   |                  ^^^^^^^^^^^^^^^ help: you can use a slice directly: `&mut [1, 2]`

error: useless use of `vec!`
##[error]  --> tests/ui/vec.rs:42:14
   |
LL |     on_slice(&vec![1, 2]);
   |              ^^^^^^^^^^^ help: you can use a slice directly: `&[1, 2]`

error: useless use of `vec!`
##[error]  --> tests/ui/vec.rs:45:18
   |
LL |     on_mut_slice(&mut vec![1, 2]);
   |                  ^^^^^^^^^^^^^^^ help: you can use a slice directly: `&mut [1, 2]`

error: useless use of `vec!`
##[error]  --> tests/ui/vec.rs:48:14
   |
LL |     on_slice(&vec!(1, 2));
   |              ^^^^^^^^^^^ help: you can use a slice directly: `&[1, 2]`

error: useless use of `vec!`
##[error]  --> tests/ui/vec.rs:51:18
   |
LL |     on_mut_slice(&mut vec![1, 2]);
   |                  ^^^^^^^^^^^^^^^ help: you can use a slice directly: `&mut [1, 2]`

error: useless use of `vec!`
##[error]  --> tests/ui/vec.rs:54:14
   |
LL |     on_slice(&vec![1; 2]);
   |              ^^^^^^^^^^^ help: you can use a slice directly: `&[1; 2]`

error: useless use of `vec!`
##[error]  --> tests/ui/vec.rs:57:18
   |
LL |     on_mut_slice(&mut vec![1; 2]);
   |                  ^^^^^^^^^^^^^^^ help: you can use a slice directly: `&mut [1; 2]`

error: useless use of `vec!`
##[error]  --> tests/ui/vec.rs:84:19
   |
LL |     let _x: i32 = vec![1, 2, 3].iter().sum();
   |                   ^^^^^^^^^^^^^ help: you can use an array directly: `[1, 2, 3]`

error: useless use of `vec!`
##[error]  --> tests/ui/vec.rs:88:17
   |
LL |     let mut x = vec![1, 2, 3];
   |                 ^^^^^^^^^^^^^ help: you can use an array directly: `[1, 2, 3]`

error: useless use of `vec!`
##[error]  --> tests/ui/vec.rs:95:22
   |
LL |     let _x: &[i32] = &vec![1, 2, 3];
   |                      ^^^^^^^^^^^^^^ help: you can use a slice directly: `&[1, 2, 3]`

error: useless use of `vec!`
##[error]  --> tests/ui/vec.rs:98:14
   |
LL |     for _ in vec![1, 2, 3] {}
   |              ^^^^^^^^^^^^^ help: you can use an array directly: `[1, 2, 3]`

error: useless use of `vec!`
##[error]  --> tests/ui/vec.rs:138:20
   |
LL |     for _string in vec![repro!(true), repro!(null)] {
   |                    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: you can use an array directly: `[repro!(true), repro!(null)]`

error: useless use of `vec!`
##[error]  --> tests/ui/vec.rs:156:18
   |
LL |     in_macro!(1, vec![1, 2], vec![1; 2]);
   |                  ^^^^^^^^^^ help: you can use an array directly: `[1, 2]`

error: useless use of `vec!`
##[error]  --> tests/ui/vec.rs:156:30
   |
LL |     in_macro!(1, vec![1, 2], vec![1; 2]);
   |                              ^^^^^^^^^^ help: you can use an array directly: `[1; 2]`

error: useless use of `vec!`
##[error]  --> tests/ui/vec.rs:177:14
   |
LL |     for a in vec![1, 2, 3] {
   |              ^^^^^^^^^^^^^ help: you can use an array directly: `[1, 2, 3]`

error: useless use of `vec!`
##[error]  --> tests/ui/vec.rs:182:14
   |
LL |     for a in vec![String::new(), String::new()] {
   |              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: you can use an array directly: `[String::new(), String::new()]`

error: useless use of `vec!`
##[error]  --> tests/ui/vec.rs:215:33
   |
LL |     this_macro_doesnt_need_vec!(vec![1]);
   |                                 ^^^^^^^ help: you can use an array directly: `[1]`

error: useless use of `vec!`
##[error]  --> tests/ui/vec.rs:242:14
   |
LL |     for a in &(vec![1, 2]) {}
   |              ^^^^^^^^^^^^^ help: you can use a slice directly: `&[1, 2]`

error: useless use of `vec!`
##[error]  --> tests/ui/vec.rs:250:13
   |
LL |     let v = &vec![];
   |             ^^^^^^^ help: you can use a slice directly: `&[]`

error: aborting due to 26 previous errors


full stdout:

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. T-libs Relevant to the library team, which will review and decide on the PR/issue. labels Oct 27, 2025

rustbot assigned SparrowLii Oct 27, 2025

RalfJung commented Oct 27, 2025

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RalfJung force-pushed the box_new branch from a3cd68b to 2ff0fae Compare October 28, 2025 07:22

RalfJung commented Oct 28, 2025

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tests/ui/issues/issue-47184.rs

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This is fully a duplicate of something already tested in nll/user-annotations/patterns.rs.

RalfJung commented Oct 28, 2025

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RalfJung force-pushed the box_new branch 2 times, most recently from 4e526d4 to cb7642b Compare October 28, 2025 07:41

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RalfJung force-pushed the box_new branch 2 times, most recently from 86e5a72 to 020bc3a Compare October 28, 2025 09:33

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RalfJung force-pushed the box_new branch from 020bc3a to a1b255c Compare October 28, 2025 11:06

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rust-bors bot added a commit that referenced this pull request Oct 28, 2025

Auto merge of #148190 - RalfJung:box_new, r=<try>

500cf8b

replace box_new with lower-level intrinsics

RalfJung force-pushed the box_new branch from 3333d57 to 4bafbdc Compare November 4, 2025 19:44

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RalfJung force-pushed the box_new branch from 4bafbdc to 6b2132b Compare November 4, 2025 20:32

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RalfJung force-pushed the box_new branch from 6b2132b to e4d0021 Compare November 4, 2025 22:57

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RalfJung force-pushed the box_new branch from e4d0021 to 18f7db1 Compare November 5, 2025 07:42

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RalfJung force-pushed the box_new branch from 18f7db1 to a1d74b2 Compare November 5, 2025 09:03

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Skgland reviewed Nov 7, 2025

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cjgillot reviewed Nov 9, 2025

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RalfJung added 3 commits November 9, 2025 12:01

replace box_new in Box::new with write_via_move

5c79d4b

requires lowering write_via_move during MIR building to make it just like an assignment

add write_box_via_move intrinsic and use it for vec!

5ff297a

This allows us to get rid of box_new entirely

move intrinsic to alloc::intrinsics

b5b80a5

RalfJung force-pushed the box_new branch from a1d74b2 to d2980c5 Compare November 9, 2025 11:02

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RalfJung added 2 commits November 9, 2025 12:57

work around debuginfo behavior change

08383ea

adjust clippy to fix some of the issues

a124479

RalfJung force-pushed the box_new branch from d2980c5 to a124479 Compare November 9, 2025 11:57

rustbot added the T-clippy Relevant to the Clippy team. label Nov 9, 2025

		// Make sure `StorageDead` gets emitted.
		this.schedule_drop_storage_and_value(expr_span, this.local_scope(), ptr);

replace box_new with lower-level intrinsics #148190

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replace box_new with lower-level intrinsics #148190

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vec! FAQ

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RalfJung commented Oct 27, 2025 •

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`vec!` FAQ

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