ABI Layer 2: prove translation preserves results — flagship Idris2 proof#42
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Add the flagship Layer-2 semantic proof for julianiser. Models a shared
arithmetic + array-indexing expression AST with two evaluators: evalSrc
(Python/R, 0-based indexing) and evalJulia (translated Julia, 1-based
indexing). Proves the headline correctness property:
translatePreserves : (env) -> (e) ->
evalSrc env e = evalJulia env (translate e)
as a genuine propositional equality by structural induction, with the
index case discharged by the 0-to-1 re-basing round-trip lemma
(juliaRoundTrip), mirroring IndexRemapCorrect in Types.idr.
Includes a sound certifier (certifyEquiv/certifyEquivSound), a positive
control (sampleAgrees, fully evaluated 10*2+30=50), and a negative
control: a deliberately unshifted "buggy" Julia evaluator together with
buggyDivergesWitness proving it genuinely diverges (30 /= 20). The
property is non-vacuous: an adversarial Refl claiming the buggy
translation preserves results is rejected by idris2 (Mismatch 20 vs 30).
No believe_me/postulate/assert_total. Builds clean, zero warnings.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01A6PSzJWpRxtzGDjUCEh7Mx
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<!-- SPDX-License-Identifier: CC-BY-SA-4.0 --> ## Summary Closes the **G34** hole: the ABI-FFI gate ran a Julia *structural* conformance check and a Zig FFI build, but **nothing ever ran `idris2` on the ABI itself**. The 8 proof modules (`Types`, `Layout`, `Foreign`, `Proofs`, `Semantics`, `Invariants`, `FfiSeam`, `Capstone` — landed across PRs #38/#42/#43/#44/#45) were authored and locally verified against Idris2 0.7.0 but never compiler-checked in CI. A future edit could break a proof and the gate would stay green. ## Changes - **`.github/workflows/abi-ffi-gate.yml`**: new `idris2-abi` job running `idris2 --typecheck julianiser-abi.ipkg` in the SHA-pinned `ghcr.io/stefan-hoeck/idris2-pack` container (the same prebuilt image the `Axiom.jl` `idris2-abi-check` job uses — avoids a ~10-min Chez/Idris2 source build). Header comment updated to describe all three jobs. - **`.tool-versions`**: uncomment `idris2 0.7.0` (pins the version the proofs were verified against, for local `asdf` use). Nothing auto-installs from it, so this is documentation-only. ## RSR Quality Checklist ### Required - [x] Tests pass — `idris2 --typecheck julianiser-abi.ipkg` and `idris2 --build julianiser-abi.ipkg` both exit 0 on all 8 modules (verified locally, Idris2 0.7.0) - [x] No banned language patterns (YAML workflow + `.tool-versions` only) - [x] No banned functions (`believe_me`/`postulate`/`sorry`) — the ABI modules are unchanged by this PR; the new job *enforces* their absence going forward - [x] SPDX headers intact (workflow retains its `MPL-2.0` header; no source files added) - [x] No secrets, credentials, or `.env` files included ### As Applicable - [x] ABI/FFI changes validated — CI now typechecks `src/interface/abi/` on every push/PR; the existing structural + Zig jobs are untouched ## Testing Ground-truthed with Idris2 0.7.0: - `cd src/interface/abi && idris2 --typecheck julianiser-abi.ipkg` → exit 0 - `idris2 --build julianiser-abi.ipkg` → exit 0 - YAML parses; job list = `conformance`, `zig-build`, `idris2-abi`; `working-directory` path `src/interface/abi/julianiser-abi.ipkg` exists. The pinned container image is the identical digest already green in `Axiom.jl`'s equivalent `idris2-abi-check` job. 🤖 Generated with [Claude Code](https://claude.com/claude-code) https://claude.ai/code/session_01UPFC9YQ7g9gc3VnRox42Q1 --- _Generated by [Claude Code](https://claude.ai/code/session_01UPFC9YQ7g9gc3VnRox42Q1)_ Co-authored-by: Claude <noreply@anthropic.com>
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Summary
Raises julianiser's Idris2 ABI to Layer 2 with its first flagship semantic proof. Julianiser's headline is auto-wrapping Python/R pipelines into Julia; the correctness obligation is that translation preserves results. This models a small expression language with a source evaluator and a Julia evaluator and proves
evalSrc env e = evalJulia env eover the AST (plus an index round-trip).Mirrors the estate flagship-proof pattern: faithful AST, real equality proven by induction, certifier proven sound, negative control.
Changes
src/interface/abi/Julianiser/ABI/Semantics.idr—Expr,evalSrc/evalJulia,juliaRoundTrip,translatePreserves(the preservation equality),certifyEquivSound, and a negative-control witness..ipkg.RSR Quality Checklist
Required
As Applicable
Testing
Verified with Idris2 0.7.0:
idris2 --build julianiser-abi.ipkg→ exit 0, zero warnings. Adversarial check: a deliberately-false proof was rejected.build/removed.🤖 Generated with Claude Code
https://claude.ai/code/session_01A6PSzJWpRxtzGDjUCEh7Mx
Generated by Claude Code