Upgrade Rust toolchain to nightly-2026-02-14

[tautschnig]

Advance from nightly-2026-02-12 to nightly-2026-02-14. One source change is required (first needed at nightly-2026-02-13); 02-14 then also passes with no further changes.

nightly-2026-02-13 introduces ty::PatternKind::NotNull (used by NonNull), which rustc_public cannot yet convert to its stable representation, so calling the stable Ty::kind() on such a pattern type panics (not yet implemented). Kani's -Z valid-value-checks pass walks every reachable type and hit this.

Detect pattern types via the internal representation (where inspecting the kind is always safe) and derive their validity from the scalar valid_range in their layout ABI, which already captures both range and non-null constraints, instead of matching on the stable kind. Thread tcx through ty_validity_per_offset, try_from_ty, and assignment_check_points for the internal check.

Additionally, two script-based-pre tests regress on this nightly and are addressed here:

• std_codegen: std itself now uses pattern-typed NonNull, so Kani cannot codegen std at all in this toolchain window — the rustc_public conversion for PatternKind::NotNull is todo!() until it was implemented upstream on nightly-2026-04-29, and it is hit from reachability and codegen paths that cannot work around an unrepresentable type. The test is disabled via the fixme path convention (directory renamed to std_codegen_fixme), with a comment in its config.yml stating that it should be re-enabled once the toolchain reaches nightly-2026-04-29. Note for reviewers: this suspends std-codegen coverage until the toolchain upgrade reaches that nightly.

• ambiguous_crate: cargo reworded its ambiguous-package-specification error. The expected output is trimmed to the durable lines of the new wording (the current wording contains an upstream typo, "specificationm", which is deliberately not matched so the eventual upstream fix does not break the test again).

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

[Copilot]

Pull request overview

Updates Kani’s Rust nightly toolchain and adjusts the -Z valid-value-checks instrumentation to avoid panicking when encountering newly introduced rustc pattern types (e.g., ty::PatternKind::NotNull used by NonNull) that rustc_public cannot yet convert to its stable Ty::kind() representation.

Changes:

• Bump toolchain from nightly-2026-02-12 to nightly-2026-02-14.
• Thread TyCtxt through the valid-value intrinsic generation and validity-walking helpers.
• Detect pattern types via the internal representation and avoid calling stable Ty::kind() on them during validity analysis.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 1 comment.

File	Description
rust-toolchain.toml	Advances the pinned nightly toolchain version.
kani-compiler/src/kani_middle/transform/kani_intrinsics.rs	Passes tcx through valid-value intrinsic generation to support internal pattern-type detection.
kani-compiler/src/kani_middle/transform/check_values.rs	Updates validity-range extraction and validity traversal to safely handle pattern types using internal APIs.

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