ABI Layer 4: prove the FFI result-code seam is injective + faithful#38
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Add Nimiser.ABI.Semantics, a machine-checked semantic proof that the Nim->C code generator preserves source signatures: same name, same arity, and every argument/return type lowered by the canonical injective nimToC mapping. An arity or type mismatch is unrepresentable as a SigPreserved witness. Contents: - Faithful model: NimT / CT type universes, NimSig / CSig signatures, total nimToC lowering, genBinding code generator. - Headline property SigPreserved with no constructor for any mismatch. - genBindingPreserves: the generator ALWAYS preserves (soundness). - nimToCInjective: the lowering is injective (non-vacuity engine). - decSigPreserved: sound + complete Dec decision procedure. - certifyBinding + certifyBindingSound tied to the project Result type; generatedAlwaysCertifies corollary. - Positive control samplePreserved (explicit witness) and three negative controls (wrong return type, wrong arity, wrong arg type), all machine-checked. Build: idris2 --build nimiser-abi.ipkg exits 0, zero warnings. Adversarial false proof (claiming a type-mismatched binding is preserved) is rejected by the type-checker, confirming non-vacuity. Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01A6PSzJWpRxtzGDjUCEh7Mx
Adds Nimiser.ABI.Invariants over the existing Semantics codegen model (NimT/CT/nimToC/NimSig/CSig/genBinding/ArgsLower), proving two facts deeper than and distinct from the Layer-2 signature-preservation theorem: 1. Composition/distributivity: lowering is a homomorphism over argument- list concatenation (lowerAppendDistrib), lifted relationally (argsLowerAppend) and to signature extension (genBindingExtendComposes, extendedArgsLower) — codegen of a grown proc is the grown codegen. 2. Whole-signature injectivity: genBindingInjective shows distinct Nim signatures lower to distinct C bindings (no symbol/ABI aliasing), strictly stronger than the Layer-2 per-type nimToCInjective lemma. Includes a sound+complete DecEq NimSig, a positive control (composed ArgsLower witness on concrete data) and negative/non-vacuity controls (distinctSigsDistinctBindings, extensionChangesBinding, decEqDistinctIsNo). Builds clean (exit 0, zero warnings); adversarial false-equality proof via genBindingInjective is rejected. No believe_me/postulate/assert_total/etc. Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01A6PSzJWpRxtzGDjUCEh7Mx
Seals the ABI<->FFI seam on the proof side: proves the Result result-code encoding is sound, complementing the structural abi-ffi-gate.py check. - intToResult: total Bits32 -> Maybe Result decoder - resultRoundTrip: faithful/lossless encoding (decode . encode = Just) - resultToIntInjective: distinct outcomes never collide on the wire, derived from the round-trip via justInjective . cong - positive controls (decode 0/7/8) and a non-vacuity negative control (Not (resultToInt Ok = resultToInt Error)), all machine-checked No ProofStatus/statusToInt or other FFI enum encoder exists in this ABI, so Result is the sole seam. Genuine total proof: no believe_me, postulate, assert_total, idris_crash, or %hint hacks. Builds clean with zero warnings. Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01A6PSzJWpRxtzGDjUCEh7Mx
Signed-off-by: Jonathan D.A. Jewell <6759885+hyperpolymath@users.noreply.github.com>
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Summary
Layer 4 (seal the ABI↔FFI seam): proves the FFI result-code encoding (
resultToInt) is a sound, lossless wire encoding — decoderintToResultwithresultRoundTrip, from whichresultToIntInjectiveis derived. Distinct ABI outcomes never collide on the C wire. Complements the structuralabi-ffi-gate.py.New module
*.ABI.FfiSeam(importsTypes). Positive + non-vacuity controls.Testing
Idris2 0.7.0
--build→ exit 0, zero warnings. Adversarial rejection confirmed.build/removed. Nobelieve_me/postulate/sorry.🤖 Generated with Claude Code
https://claude.ai/code/session_01A6PSzJWpRxtzGDjUCEh7Mx
Generated by Claude Code