Autoharness: support pattern types (RigidTy::Pat) - #4780
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Teach autoharness to recognize and generate values for pattern types, since nightly-2026-04-01. Without this, any function taking a NonNull argument (or a struct containing one) is skipped with 'Missing Arbitrary'. Resolves model-checking#4758
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Tianshu-Huang
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September 3, 2026 23:54
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Problem
Since
nightly-2026-04-01,NonNull<T>wraps apattern_type!(*const T is !null)instead of a bare*const T. Sincenightly-2026-06-01(#4760),rustc_layout_scalar_valid_range_start/endattributes were replaced by pattern types more broadly. Autoharness does not recognizeRigidTy::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) — recognizeRigidTy::Patin both the struct-field iteration loop and the top-level type match, delegating to a new helperpat_base_is_derivable. For raw-pointer bases (*const T), the pointeeTmust be derivable (because the raw-pointer codegen allocates storage for it); for any other base (integers, etc.) the base itself must be derivable.call_kani_any_for_ty(automatic.rs) — generate a nondeterministic value of the base type, transmute it to the pattern type, then constrain it to the pattern's validity range via the existingassume_scalar_niche.Tests
Updated
autoharness_niche:Month,Schedule,PosI8, andcheck_monthly::<Month>move from skipped to verified (10/10 functions pass), satisfying the acceptance criteria in #4758.New
autoharness_pattern_type: coversNonNull<u8>as a direct argument,NonNull<u32>inside a struct field, and a cover check verifying the generated value is non-null.Resolves #4758
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