Upgrade Rust toolchain to nightly-2026-06-01 by feliperodri · Pull Request #4760 · model-checking/kani

feliperodri · 2026-08-25T17:52:48Z

Description

Bumps rust-toolchain.toml from nightly-2026-05-01 to nightly-2026-06-01. Four upstream changes drive most of this.

1. `Retag` moved onto `Rvalue::Use`

StatementKind::Retag and RetagKind are gone; Rvalue::Use now carries a WithRetag flag instead:

Use(Operand, WithRetag),

Kani never modelled retags (they are Stacked-Borrows/Miri only), so the statement arms are dropped, the flag is ignored when reading a Use, and synthesized Uses pass WithRetag::No. internal_mir's RetagKind conversion becomes a WithRetag one.

2. `Variants::Multiple` stores a `VariantLayout`, not a `LayoutData`

The new type carries only per-field offsets — no FieldsShape (so no field order) and no alignment. Variant layouts now come from Layout::for_variant, which is what rustc_codegen_ssa does and which restores the field order. A new variant_layout helper is used by both the type side (codegen_enum_cases) and the value side (codegen_aggregate), so the goto struct's components and the operands initializing them cannot disagree.

That change bit back: for_variant reports the enum's align for a variant (align: parent.align), which over-pads every variant and inflates the enum. check_vtable_size caught it as an ICE on tests/cargo-kani/iss2857 (48 vs 55 bytes). So codegen_struct_fields/codegen_alignment_padding now take the align explicitly, and a variant's own align is computed as the maximum of its fields' aligns — which is what the per-variant LayoutData used to carry.

3. `rustc_layout_scalar_valid_range_start`/`_end` were removed

Replaced by pattern types, the same move core::num::niche_types made. The tests that define ranged scalar newtypes are converted to std::pat::pattern_type!.

This narrows the layout-niche feature added in #4716: a pattern type is not an ADT and has no Arbitrary implementation, so can_derive_arbitrary cannot synthesize a struct that has one as a field, and locally-defined ranged types are now skipped rather than harnessed. The assumption still works end to end through std::time::Duration (the motivating case from the #3832 triage), and tests/script-based-pre/autoharness_niche pins both halves so the reduced reach is asserted by a test rather than silent. Tracked in #4758 with a concrete fix sketch.

4. New `Rvalue::Reborrow`

User-definable reborrowing of ADTs via CoerceShared. It is documented as a bitwise copy today, but the same docs anticipate it changing memory layout, so codegen reports it as an unsupported construct rather than silently modelling it as a copy. The points-to analysis treats it as pointing wherever its place does.

Assorted API changes

Change	Site
`CodegenBackend` moved `CrateInfo` from `codegen_crate` to `join_codegen`	both backends' `compiler_interface.rs`
`rustc_data_structures::stable_hasher` renamed to `stable_hash`; `HashStable`/`hash_stable` to `StableHash`/`stable_hash`	`reachability.rs`
The `normalize` callback of `ptr_metadata_ty{,_or_tail}` now takes `Unnormalized`	`typ.rs`
More `FieldDef::ty` and `instantiate*` sites need `.skip_normalization()`	`typ.rs`, `intrinsics.rs`
`TagEncoding::Niche`'s `niche_variants` is the lang `RangeInclusive` (public `start`/`last` fields, not methods)	`rvalue.rs`, `statement.rs`
New `useless_borrows_in_formatting` clippy lint	11 sites across the workspace

Test change worth calling out

vtable_size_align_drop no longer asserts the exact identity of the vtable's drop pointer. Traced with Kani's debug logging: the drop-glue shim is now core::ptr::drop_glue::<T> rather than core::ptr::drop_in_place::<T>, and drop_glue is not nameable from source. It checks the slot is populated instead; the size and align fields the test is named for are unchanged. This weakens the test — it no longer checks the slot holds the drop glue for the right type — so it is tracked in #4759 with options for restoring that coverage.

Both of these failures were confirmed to be genuine nightly-2026-06-01 regressions rather than pre-existing fragility, by rebuilding the parent commit against nightly-2026-05-01, where both pass.

`drop_in_place` now takes a reference to reach the drop glue

Related to the same rename: core::ptr::drop_in_place used to be the drop lang item, with its body replaced wholesale by the compiler. It is now a wrapper that calls the new drop_glue lang item through &mut *to_drop, and creating that reference asserts the pointee is aligned and valid — so dropping through a raw pointer carries a precondition it did not before.

That surfaced in expected/loop-contract/loop_assigns_for_vec.rs, whose loop_modifies havocs the word holding v.len() while the invariant only constrains i; the drop after the loop then sees an unconstrained length. Strengthening the invariant with v.len() == i * 3 + 3 is rejected (Rust intrinsic assumption failed), so expressing what the drop needs looks like a loop-contracts limitation rather than something this PR can fix. The test is renamed loop_assigns_for_vec_fixme.rs with the analysis recorded in the file, tracked in #4761. Verified that Vec's internal layout is unchanged, so the test's hard-coded .add(2) offset for len is still correct.

Two contract tests that deliberately pin a total check count needed their numbers updated: capture_load_checks_elided 36 → 34 and capture_load_user_deref_pass 60 → 58 (two checks in read_answer's own body became unreachable). In both cases the assertion the test actually exists for still holds — no user-facing pointer_dereference group came back in the first, and the pinned {closure#3}::{closure#0}.pointer_dereference.1 - Status: SUCCESS is still present in the second — so the counts were updated with a note in each test explaining that the total is plumbing-sensitive and what it still guards against.

Testing

Local, macOS aarch64, CBMC 6.10.0 (cbmc-6.9.0-214-g45436eea34), all re-run after rebasing onto current main (which now includes #4717, whose new Rvalue::Use construction site also needed the WithRetag argument):

Suite	Result
`kani`	607 passed, 0 failed, 23 ignored
`cargo-kani`	71 passed, 0 failed
`script-based-pre`	68 passed, 0 failed, 1 ignored
`std-checks`	5 passed, 0 failed
`cargo-ui`	30 passed, 0 failed
`coverage`	20 passed, 0 failed
`ui`	151 passed, 2 failed — both the `cadical` tests, see below
`expected`	474 passed, 0 failed, 16 fixme/ignored
`prusti` / `smack` / `kani-docs` / `json-handler` / `cargo-coverage` / `firecracker`	8 / 40 / 13 / 5 / 2 / 0 passed, 0 failed

Other gates, all clean:

cargo build-dev
cargo build-dev -- --features cprover --features llbc
cargo clippy --workspace --tests and RUSTFLAGS="--cfg=kani_sysroot" cargo clippy --workspace
./scripts/kani-fmt.sh --check
RUSTFLAGS="-D warnings" cargo build --no-default-features --features cprover
Unit tests: cprover_bindings, kani-compiler, kani-driver, kani_metadata, kani --features concrete_playback, kani_macros

Environment caveat: this CBMC build has no cadical, so ui/solver-{attribute,option}/cadical fail locally on output text only ("The specified solver, 'cadical', is not available"), and expected/shadow/slices/slice_split is very slow under the MiniSat fallback. Both are expected to be clean on CI.

Towards #4758, #4759, #4761.

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 and MIT licenses.

Four upstream changes drive most of this. **Retag moved onto `Rvalue::Use`.** `StatementKind::Retag` and `RetagKind` are gone; `Rvalue::Use` now carries a `WithRetag` flag instead. Kani never modelled retags (they are Stacked-Borrows/Miri only), so the statement arms are dropped, the flag is ignored when reading a `Use`, and synthesized `Use`s pass `WithRetag::No`. `internal_mir`'s `RetagKind` conversion becomes a `WithRetag` one. **`Variants::Multiple` stores a `VariantLayout`, not a `LayoutData`.** The new type carries only per-field offsets -- no `FieldsShape` (so no field order) and no alignment. Variant layouts now come from `Layout::for_variant`, which is what `rustc_codegen_ssa` does and restores the field order; a new `variant_layout` helper is used by both the type side (`codegen_enum_cases`) and the value side (`codegen_aggregate`) so the goto struct's components and the operands initializing them cannot disagree. `for_variant` reports the *enum's* align for a variant (`align: parent.align`), which would over-pad every variant and inflate the enum -- caught by `check_vtable_size` on `tests/cargo-kani/iss2857` (48 vs 55 bytes). So `codegen_struct_fields`/`codegen_alignment_padding` now take the align explicitly, and a variant's own align is computed as the maximum of its fields' aligns, which is what the per-variant `LayoutData` used to carry. **`rustc_layout_scalar_valid_range_start`/`_end` were removed** in favour of pattern types, the same move `core::num::niche_types` made. The tests that define ranged scalar newtypes are converted to `std::pat::pattern_type!`. Note the consequence for autoharness: a pattern type is not an ADT and has no `Arbitrary` implementation, so `can_derive_arbitrary` cannot synthesize a struct that has one as a field, and locally-defined ranged types are now skipped rather than harnessed. The niche assumption added in model-checking#4716 is still exercised end to end through `std::time::Duration`; `tests/script-based-pre/autoharness_niche` pins both halves so the reduced reach is asserted rather than silent. **New `Rvalue::Reborrow`** (user-definable reborrowing of ADTs via `CoerceShared`). It is documented as a bitwise copy today, but the same docs anticipate it changing memory layout, so codegen reports it as an unsupported construct rather than silently modelling it as a copy. The points-to analysis treats it as pointing wherever its place does. Also adapts to: the `CodegenBackend` trait moving `CrateInfo` from `codegen_crate` to `join_codegen` (both backends), `rustc_data_structures:: stable_hasher` being renamed to `stable_hash` with `HashStable`/`hash_stable` becoming `StableHash`/`stable_hash`, the `normalize` callback of `ptr_metadata_ty{,_or_tail}` now taking `Unnormalized`, more `FieldDef::ty` and `instantiate*` sites needing `.skip_normalization()`, `TagEncoding::Niche`'s `niche_variants` becoming the lang `RangeInclusive` (public `start`/`last` fields), and the new `useless_borrows_in_formatting` clippy lint. The `vtable_size_align_drop` test no longer asserts the exact identity of the vtable's drop pointer: the drop-glue shim is now `core::ptr::drop_glue::<T>` rather than `core::ptr::drop_in_place::<T>`, and `drop_glue` is not nameable from source. It checks the slot is populated instead; the size and align fields that the test is named for are unchanged.

feliperodri · 2026-08-25T22:16:07Z

The next upgrade, nightly-2026-07-01, is up as a draft in #4764 stacked on this one. It is much smaller (no verification behaviour changed and no test needed adjusting) and should be reviewed once this lands.

…del-checking#4766) ## Description `cargo_build` hardcoded the compiler output directory as `target/kani/<triple>/debug/deps`, and `cargo_project` then canonicalized it. That layout is cargo's to choose, and **cargo 1.99 changes it**: artifacts no longer share `debug/deps` — each package gets its own `debug/build/PKG/HASH/out/` — so `debug/deps` is never created and the canonicalize fails: ``` error: No such file or directory (os error 2) ``` Artifact *discovery* was already layout-agnostic: `map_kani_artifact` derives every path from the `filenames` that cargo reports. The hardcoded directory was the only thing tying the driver to the old layout. This PR: - Derives `CargoOutputs::outdir` from the discovered artifacts instead of assuming a path. - Drops the `canonicalize` in `cargo_project`. An artifact path is canonical already (`Artifact::try_new` canonicalizes), and the no-artifacts fallback names a directory cargo had no reason to create — canonicalizing it turns a benign case into a hard error. - Makes two tests layout-agnostic: `check-output` searches the target directory for its `--gen-c` output, and `cargo_playback_opts` asserts only the *file name* of the executable whose path cargo itself reports. Note that with cargo 1.99 a multi-package build no longer has a single output directory. `outdir` names one of them; it feeds only the `output_dir` field of the `-Z unstable-options` JSON frontend, and previously named a directory that under 1.99 does not exist at all. The doc comment says so explicitly. The layout change, confirmed locally on nightly-2026-08-01 (cargo 1.99.0-nightly): ``` # cargo 1.97 target/kani/<triple>/debug/deps/<pkg>-<hash>.kani-metadata.json # cargo 1.99 -- one directory per package, no debug/deps at all target/kani/<triple>/debug/build/<pkg>/<hash>/out/<pkg>-<hash>.kani-metadata.json ``` ## Why this is a standalone PR This unblocks the toolchain upgrade chain. It has no dependency on any toolchain bump and is behaviour-preserving on the current toolchain, so it can land on its own. The intended order is model-checking#4760 (2026-06-01) → model-checking#4764 (2026-07-01) → this PR → the 2026-08-01 bump, which is blocked on it. ## Testing **On the current toolchain (nightly-2026-05-01, cargo 1.97 — old layout):** - `cargo-kani`: 71 passed, 0 failed - `script-based-pre`: 70 passed, 2 failed — both failures (`cargo_autoharness_filter`, `cargo_autoharness_slices`) reproduce on unmodified `main` and are unrelated to this change - `cargo test -p kani-driver`: 93 passed - `./scripts/kani-fmt.sh --check`, `cargo clippy --workspace --tests -- -D warnings`, `RUSTFLAGS="--cfg=kani_sysroot" cargo clippy --workspace -- -D warnings`: clean **Cherry-picked onto the local 2026-08-01 branch (cargo 1.99 — new layout), which is where the bug bites:** | Suite | Before | After | |---|---|---| | `cargo-kani` | 68 failed | **71 passed, 0 failed** | | `script-based-pre` | 11 failed | **68 passed, 0 failed** | - Was this change tested? **Yes** - Is this a breaking change? **No** By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 and MIT licenses.

### Description Bumps `rust-toolchain.toml` from `nightly-2026-07-01` to `nightly-2026-08-01`, the first 1.99 nightly. 91 compile errors came with it. #### 1. `Statement`/`Terminator` carry a `SourceInfo`, not a bare `Span` (78 of the 91 errors) ```rust // nightly-2026-07-01 pub struct Statement<'tcx> { pub source_info: SourceInfo, .. } // Terminator: span only // nightly-2026-08-01 -- both carry SourceInfo (span + source scope) ``` A new helper in `transform/body.rs` keeps the choice of scope in one documented place rather than spreading a bare `scope: 0` across ~78 sites: ```rust /// The `SourceInfo` for a statement or terminator that Kani synthesizes at `span`. /// /// As of nightly-2026-08-01 `Statement` and `Terminator` carry a `SourceInfo` (span plus source /// scope) instead of a bare `Span`. Kani-synthesized MIR does not belong to any inlined scope, so /// it uses the outermost one -- scope 0, which `Body::new` always allocates. pub fn synthetic_source_info(span: Span) -> SourceInfo { SourceInfo { span, scope: 0 } } ``` Reads become `.source_info.span`. #### 2. `predicates_of` became `clauses_of` Returns `GenericClauses` (`parent` + `clauses`) instead of `GenericPredicates` (`parent` + `predicates`). Same shape and same `instantiate`, so this is a rename at four call sites — three in `codegen_units.rs` from model-checking#4706/model-checking#4718, one in the LLBC backend. #### 3. `ty::FnDef`'s generic args are bound Three `Instance::{try,expect}_resolve` call sites need `.skip_binder()`. #### 4. `ValueAbi::ScalarPair` became a struct variant With a new `b_offset` field. #### 5. Two new enum variants - `AssertMessage::NullReferenceConstructed` — handled like `NullPointerDereference`: same property class, description taken from `rustc_public` rather than hardcoded. - `InstanceKind::LlvmIntrinsic` — codegens like any other item, and has no Rust body for reachability to collect. Plus `LocalModDefId` renamed to `LocalModId`, and `Region::new_early_param` moving to the `RegionExt` extension trait. ### Test changes (5 files) **`std::intrinsics::{size_of,align_of}` are now comptime fns** and cannot be called at runtime, which affected four tests: - `tests/kani/DynTrait/{nested_boxes,vtable_size_align_drop}.rs` used `size_of` incidentally, to compare a vtable field against a type's size — switched to `std::mem::size_of`. - `tests/kani/Intrinsics/ConstEval/{size_of,align_of}.rs` exist to check the intrinsics themselves, so each call is bound to a `const` — which is what that directory is about, and the only way now legal. **`expected/issue-3571` — a genuine behaviour change worth flagging.** Constructing a null reference (`&*(0 as *const u32)`) used to report `null pointer dereference occurred`; rustc now distinguishes constructing a null reference from dereferencing a null pointer and reports `null reference produced`. rustc also emits a new `misaligned pointer to reference cast` check at the same site. The UB is still caught and the harness still fails — only the wording is more precise — so the expectation follows rustc's message rather than pinning the old one. No other test needed adjusting, and no verification behaviour changed. ### Testing Local, macOS aarch64, CBMC 6.10.0 (`cbmc-6.9.0-214-g45436eea34`), on the stack rebased onto current `main` (which now includes model-checking#4760): | Suite | Result | |---|---| | `kani` | **607 passed, 0 failed** | | `cargo-kani` | **71 passed, 0 failed** | | `cargo-ui` | **30 passed, 0 failed** | | `expected` | 471 passed, 2 failed — see below | | `ui` | 151 passed, 2 failed — environmental, see below | Also clean: both the CPROVER and LLBC builds, `cargo clippy --workspace --tests -- -D warnings`, `RUSTFLAGS="--cfg=kani_sysroot" cargo clippy --workspace -- -D warnings`, and `./scripts/kani-fmt.sh --check`. The two `expected` failures were run before the fix above and are accounted for: - `expected/issue-3571` — the null-reference wording change; **fixed in this PR**, verified passing. - `expected/shadow/slices/slice_split` — I interrupted this one to let the suite finish. It is **not** an 08-01 regression: I timed it on the 07-01 branch as a control and it is equally slow there (>20 min in CBMC's SAT solver on both), so it is a slow test on this machine rather than anything this upgrade introduced. CI covers it. The two `ui` failures are `solver-attribute/cadical` and `solver-option/cadical`, both expecting `Solving with CaDiCaL`. My local CBMC build reports `The specified solver, 'cadical', is not available. The default solver will be used instead.` — a missing solver in my environment, independent of the Rust toolchain. - Was this change tested? **Yes** - Is this a breaking change? **No** By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 and MIT licenses.

## Problem Since `nightly-2026-04-01`, `NonNull<T>` wraps a `pattern_type!(*const T is !null)` instead of a bare `*const T`. Since `nightly-2026-06-01` (model-checking#4760), `rustc_layout_scalar_valid_range_start/end` attributes were replaced by pattern types more broadly. Autoharness does not recognize `RigidTy::Pat` — any function whose signature involves a pattern type (directly or through a struct field) is skipped with "Missing Arbitrary implementation". ## Solution **`can_derive_arbitrary` (`mod.rs`)** — recognize `RigidTy::Pat` in both the struct-field iteration loop and the top-level type match, delegating to a new helper `pat_base_is_derivable`. Raw-pointer bases (NonNull<T>'s field) are not supported: the pointee storage would be a local of the synthesized any() and dangle on return. NonNull is a follow-up PR. **`call_kani_any_for_ty` (`automatic.rs`)** — generate a value of the base type, constrain it via assume_scalar_niche, then transmute — assuming first keeps it valid under -Z valid-value-checks. ## Tests **Updated `autoharness_niche`**: `Month`, `Schedule`, `PosI8`, and `check_monthly::<Month>` move from skipped to verified (10/10 functions pass), satisfying the acceptance criteria in model-checking#4758. **New `autoharness_pattern_type`**: an integer pattern type as a struct field and as a top-level argument, run with -Z valid-value-checks. Resolves model-checking#4758 By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 and MIT licenses. --------- Co-authored-by: Felipe R. Monteiro <felisous@amazon.com>

… length (model-checking#4896) The nightly-2026-06-01 upgrade (model-checking#4760) disabled `tests/expected/loop-contract/loop_assigns_for_vec.rs` (renamed to `loop_assigns_for_vec_fixme`, tracked in model-checking#4761): dropping `v` after the loop now creates a reference to it, which requires the loop contract to establish the vector's length, and the natural invariant `v.len() == i * 3 + 3` is rejected ("Rust intrinsic assumption failed"). The length word can instead be read through the same raw pointer the test's `loop_modifies` clause already uses (`(&v as *const Vec<u8> as *const usize).add(2)`). With that invariant the test passes again with its original expected output, so this restores the loop-contract coverage for `Vec`. The file now documents why the invariant takes this form. Manually checked that the test is not vacuous: adding `assert!(v.len() == 12 && i == 3)` after the loop verifies, while `assert!(v.len() == 11)` fails. model-checking#4761 remains open for the `v.len()` form of the invariant. By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 and MIT licenses. Co-authored-by: Kiro <kiro-agent@users.noreply.github.com>

feliperodri requested review from a team as code owners August 25, 2026 17:52

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Autoharness: generate values for pattern-type fields, restoring layout-niche coverage for user-defined ranged types #4758

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vtable_size_align_drop no longer checks the drop slot holds the right type's drop glue #4759

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loop_modifies over a Vec no longer establishes drop_in_place's new reference-creation precondition #4761

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Upgrade Rust toolchain to nightly-2026-07-01 #4764

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Merge branch 'main' into toolchain-2026-06-01

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Add WithRetag argument to Rvalue::Use sites merged from main

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Derive the cargo output directory from cargo's reported artifacts #4766

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Upgrade Rust toolchain to nightly-2026-08-01 #4767

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Autoharness: support pattern types (RigidTy::Pat) #4780

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Re-enable loop_assigns_for_vec with an invariant that establishes the length #4896

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Upgrade Rust toolchain to nightly-2026-06-01 - #4760

Upgrade Rust toolchain to nightly-2026-06-01#4760
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feliperodri commented Aug 25, 2026 • edited Loading Uh oh! There was an error while loading. Please reload this page.

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Description

1. Retag moved onto Rvalue::Use

2. Variants::Multiple stores a VariantLayout, not a LayoutData

3. rustc_layout_scalar_valid_range_start/_end were removed

4. New Rvalue::Reborrow

Assorted API changes

Test change worth calling out

drop_in_place now takes a reference to reach the drop glue

Testing

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feliperodri commented Aug 25, 2026 •

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1. `Retag` moved onto `Rvalue::Use`

2. `Variants::Multiple` stores a `VariantLayout`, not a `LayoutData`

3. `rustc_layout_scalar_valid_range_start`/`_end` were removed

4. New `Rvalue::Reborrow`

`drop_in_place` now takes a reference to reach the drop glue