Upgrade Rust toolchain to nightly-2026-02-06#4655
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tautschnig merged 3 commits intoJul 23, 2026
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Pull request overview
Updates Kani to a newer nightly and adapts the StableMIR body retrieval path to handle Rust’s change in how ADT constructor MIR is provided, avoiding panics when constructors from external crates are used as function values.
Changes:
- Bump Rust toolchain to
nightly-2026-02-06. - Add a targeted fallback that reconstructs constructor bodies via internal rustc APIs when
rustc_public::Instance::body()returnsNone.
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Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.
| File | Description |
|---|---|
| rust-toolchain.toml | Updates the pinned nightly toolchain to nightly-2026-02-06. |
| kani-compiler/src/kani_middle/transform/mod.rs | Reconstructs missing StableMIR bodies for ADT constructors when Instance::body() is unavailable, preventing .unwrap() panics. |
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rust-lang/rust stopped encoding *optimized* MIR for ADT constructors (`instance_mir` uses `mir_for_ctfe` for them). As a result, `rustc_public::Instance::body()` returns `None` for constructors imported from other crates (its `has_body` check keys off `is_mir_available`, i.e. optimized MIR), so codegenning a constructor used as a function value (e.g. `.map(Some)`) panicked on `instance.body().unwrap()`. Reconstruct the missing constructor body the same way `rustc_public`'s `BodyBuilder` would (fetch `instance_mir`, monomorphize, convert to stable MIR) when `body()` is `None` and the instance is a constructor; any other bodyless instance still panics. A regression test is added under `tests/kani/FunctionCall/ctor_as_fn_value.rs`, exercising cross-crate constructors (`Some`, `std::num::Wrapping`) and a local constructor used as function values; the cross-crate harnesses panic the compiler without this fix. Co-authored-by: Kiro <kiro-agent@users.noreply.github.com>
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rust-lang/rust stopped encoding optimized MIR for ADT constructors (
instance_mirusesmir_for_ctfefor them). As a result,rustc_public::Instance::body()returnsNonefor constructors imported from other crates (itshas_bodycheck keys offis_mir_available, i.e. optimized MIR), so codegenning a constructor used as a function value (e.g..map(Some)) panicked oninstance.body().unwrap().Reconstruct the missing constructor body the same way
rustc_public'sBodyBuilderwould (fetchinstance_mir, monomorphize, convert to stable MIR) whenbody()isNoneand the instance is a constructor; any other bodyless instance still panics.By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 and MIT licenses.