Upgrade Rust toolchain to nightly-2026-02-20 - #4713
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Advance from nightly-2026-02-18 to nightly-2026-02-20. One set of source changes
is required (first needed at nightly-2026-02-19); 02-20 then passes with no
further changes.
Three rustc changes needed handling:
1. `Rvalue::ShallowInitBox` was removed (rust-lang/rust "Remove ShallowInitBox").
Box construction no longer produces this rvalue: `Box::new` now allocates,
`write_via_move`s the value, and transmutes the pointer, while `vec!` uses the
new `write_box_via_move` intrinsic. Remove Kani's now-dead `ShallowInitBox`
match arms across codegen, analysis, points-to, check-values, the MIR visitor,
internal-MIR conversion, and the LLBC backend.
2. The `rustc_allow_const_fn_unstable` feature/attribute was removed. Drop it from
the vendored `VecDeque` sources used by the `vecdeque-cve` test.
3. The `E0433` diagnostic was reworded ("failed to resolve: could not find" ->
"cannot find"); update the `unsupported-annotation` UI test's expected output.
Co-authored-by: Kiro <kiro-agent@users.noreply.github.com>
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Pull request overview
Updates Kani’s pinned Rust nightly toolchain to nightly-2026-02-20 and adjusts the codebase/tests to accommodate upstream rustc changes introduced between nightly-2026-02-18 and nightly-2026-02-20.
Changes:
- Bump pinned toolchain from
nightly-2026-02-18tonightly-2026-02-20. - Remove now-dead handling for
Rvalue::ShallowInitBoxacross Kani’s MIR conversion/visitors/analyses/backends. - Update tests for removed
rustc_allow_const_fn_unstableand the updatedE0433wording.
Reviewed changes
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Show a summary per file
| File | Description |
|---|---|
| tests/ui/unsupported-annotation/expected | Updates expected diagnostic text for the reworded E0433 message. |
| tests/cargo-kani/vecdeque-cve/src/raw_vec.rs | Drops removed #[rustc_allow_const_fn_unstable(const_fn)] attribute from vendored VecDeque code. |
| tests/cargo-kani/vecdeque-cve/src/harness.rs | Removes the now-removed #![feature(rustc_allow_const_fn_unstable)] feature gate. |
| rust-toolchain.toml | Advances the pinned nightly toolchain to nightly-2026-02-20. |
| kani-compiler/src/kani_middle/transform/internal_mir.rs | Removes internal MIR conversion for the deleted ShallowInitBox rvalue. |
| kani-compiler/src/kani_middle/transform/check_values.rs | Removes ShallowInitBox handling from value-check visitor logic. |
| kani-compiler/src/kani_middle/transform/body.rs | Removes ShallowInitBox handling from the mutable MIR visitor traversal. |
| kani-compiler/src/kani_middle/points_to/points_to_analysis.rs | Removes ShallowInitBox from points-to successors computation. |
| kani-compiler/src/kani_middle/analysis.rs | Removes ShallowInitBox from rvalue key classification. |
| kani-compiler/src/codegen_cprover_gotoc/codegen/rvalue.rs | Removes codegen for ShallowInitBox rvalues in the CBMC/GotoC backend. |
| kani-compiler/src/codegen_aeneas_llbc/mir_to_ullbc/mod.rs | Drops the ShallowInitBox match arm from the experimental LLBC backend translation. |
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PR #4712 supersede this one |
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Advance from nightly-2026-02-18 to nightly-2026-02-20. One set of source changes is required (first needed at nightly-2026-02-19); 02-20 then passes with no further changes.
Three rustc changes needed handling:
Rvalue::ShallowInitBoxwas removed (rust-lang/rust "Remove ShallowInitBox"). Box construction no longer produces this rvalue:Box::newnow allocates,write_via_moves the value, and transmutes the pointer, whilevec!uses the newwrite_box_via_moveintrinsic. Remove Kani's now-deadShallowInitBoxmatch arms across codegen, analysis, points-to, check-values, the MIR visitor, internal-MIR conversion, and the LLBC backend.The
rustc_allow_const_fn_unstablefeature/attribute was removed. Drop it from the vendoredVecDequesources used by thevecdeque-cvetest.The
E0433diagnostic was reworded ("failed to resolve: could not find" ->"cannot find"); update the
unsupported-annotationUI test's expected output.By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 and MIT licenses.