refactor(stark): uniform Coset trait, fallible LiftedDomain constructors#993
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refactor(stark): uniform Coset trait, fallible LiftedDomain constructors#993
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Adds a `Coset<F>` trait with required `(log_size, shift, generator)` plus defaults for `size`, `point_at`, `points`, `bit_reversed_points`, `vanishing_at`, `contains`, `generator_inverse`, and a cached `shift_inverse` (`F::ONE` for subgroup; stored field on coset). Both `TwoAdicSubgroup` and `TwoAdicCoset` impl the trait; `LiftedDomain` does not — composing a trace subgroup and an LDE coset, it disambiguates via explicit `trace_subgroup()` / `lde_coset()` accessors rather than silently picking one vanishing polynomial. Drops dead/redundant `LiftedDomain` methods (`points`, `bit_reversed_points`, `point_at`, `lde_subgroup`, `is_in_*`, `is_lifted`, `blowup`, `max_lde_height`, `log_max_lde_height`, `log_lift_ratio` getter, `lifted_trace_vanishing_at`); call sites now go through `domain.lde_coset()`. Selector logic (`selectors`, `selectors_at`) moves from the coset/subgroup types into `LiftedDomain` where the lift-ratio context lives. `log_blowup` returns `u8` to match its sibling `log_*` accessors. Also renames `*coset` bindings/params/fields holding `LiftedDomain` to `*domain` for consistency, and threads `Committed::max_domain` / `FriTranscript<&TwoAdicSubgroup>` to keep the type-driven height metadata flowing. Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
…domains `LiftedDomain::canonical`, `sub_domain`, `evaluation_coset`, and `selectors` now return `Result<_, DomainError>`. Construction success is the validation evidence: holding a `LiftedDomain<F>` means its parameters are bounds-checked. Verifier and prover entry points propagate errors via `?`; downstream sites that derive from validated inputs use `.expect()` with strings documenting the upstream check. Added `LiftedDomain::sub_domains(impl IntoIterator<Item = u8>)` for the common "build per-instance sub-domains from a list of heights" pattern, collapsing a 5-line `iter().map().collect::<Result<_, _>>()` chain to one accessor. `commit_traces` now takes `&[LiftedDomain<F>]` instead of a separate `max_domain` and re-deriving sub-domain shifts internally — the prover already builds the per-instance domains, so threading them through removes a fragile `sub_domain(h).expect().lde_shift()` chain and the `assert_eq!(traces.last().height(), max_domain.trace_height())` check (now per-trace, stronger). Renamed `instance::validate_inputs` to the method `InstanceShapes::validate`, returning the validated max log trace height. AIR/instance-contract checks live there; LDE-bound checks moved to `LiftedDomain::canonical`. Added `LogTraceHeightTooLarge` variant to `InstanceValidationError` to keep `validate` panic-free against adversarial `1usize << log_h` overflow. `DomainError` is wired into both `VerifierError` and `ProverError` via `#[from]`. New tests: `canonical_too_large_returns_error`, `sub_domain_too_large_returns_error`, `evaluation_coset_too_large_returns_error`, and `malformed_log_trace_heights_is_rejected` updated to distinguish the two failure paths. Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
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Summary
Reshapes the lifted-STARK domain layer (
miden-lifted-stark) into a small hierarchy with explicit fallibility, eliminating ambient panic risk in the verifier path.Coset hierarchy (commit 1,
65b7ef9c7):domain.rsmodule withTwoAdicSubgroup<F>⊂TwoAdicCoset<F>⊂LiftedDomain<F>.Cosettrait owns the shared(log_size, shift, generator)interface and provides default bodies forpoints,bit_reversed_points,vanishing_at,contains,point_at,size,generator_inverse,shift_inverse(cached).LiftedDomaindeliberately does not implementCoset— it composes a trace subgroup and an LDE coset; callers saydomain.trace_subgroup()ordomain.lde_coset()to disambiguate vanishing polynomials.LiftedDomainaccessors that silently picked the LDE side.LiftedDomainwhere the lift ratio lives.Fallible constructors + statically-validated batch domains (commit 2,
29f2584a9):LiftedDomain::canonical,sub_domain,evaluation_coset,selectorsnow returnResult<_, DomainError>. Holding aLiftedDomain<F>is the validation evidence.InstanceShapes::validate(renamed fromvalidate_inputs) returns the validated max log trace height; LDE-bound checks moved toLiftedDomain::canonical.LiftedDomain::sub_domains(impl IntoIterator<Item = u8>)collapses the per-instance sub-domain construction to one accessor.commit_tracestakes&[LiftedDomain<F>]instead of re-deriving sub-domain shifts internally.DomainErrorflows into bothVerifierErrorandProverErrorvia#[from].Test plan
cargo test -p miden-lifted-stark(92 tests pass)cargo check -p miden-lifted-stark --benches --features testingmake docmake lint(clippy + fmt + taplo + typos all clean;cargo shearstep skipped — tool not installed locally)🤖 Generated with Claude Code