ABI Layer 2: prove generated max is correct-by-construction (flagship Idris2 proof)#39
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Add Dafniser.ABI.Semantics raising the Idris2 ABI to Layer 2 with a genuine,
machine-checked semantic proof of the repo's headline ("correct-by-construction
code generation").
Model: a Dafny spec as the postcondition MaxPost a b r — a real proposition
inhabited only when r dominates both inputs and equals one of them. The
generated body genMax returns its result paired with a MaxPost proof
(correct-by-construction). genMaxCorrect derives all three ensures conjuncts
(result>=a, result>=b, result==a||result==b) for all inputs; noUndershootLeft
refutes the bad case. A sound certifier (certifyMax/certifyMaxSound) emits the
ABI's VerificationResult. Positive control maxPositive : MaxPost 7 3 7 and
negative control maxNegative : Not (MaxPost 7 3 2) are machine-checked; an
adversarial false proof (MaxPost 7 3 2) is rejected by idris2, confirming
non-vacuity.
Builds clean (idris2 0.7.0, exit 0, zero warnings).
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01A6PSzJWpRxtzGDjUCEh7Mx
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Summary
Raises dafniser's Idris2 ABI to Layer 2 with its first flagship semantic proof. Dafniser's headline is "generate correct-by-construction code"; this models a Dafny spec (precondition + postcondition + generated body) for a representative generated function — integer
max— and proves in the type system that the generated body meets its postcondition (result ≥ a ∧ result ≥ b ∧ (result = a ∨ result = b)) for all inputs. Incorrect results are unprovable.Mirrors the estate's flagship-proof pattern (InjectionFree / Partition / Octad): faithful model, a proposition with no inhabitant for the bad case, a sound+complete
Dec, a certifier proven sound, and positive + negative controls.Changes
src/interface/abi/Dafniser/ABI/Semantics.idr—MaxPostpostcondition (LTE-backed),genMaxreturning result-with-proof,genMaxCorrect(all three conjuncts),decMaxPost,certifyMaxSound, a no-undershoot soundness lemma, positive control (MaxPost 7 3 7) and negative control (Not (MaxPost 7 3 2)).dafniser-abi.ipkg.RSR Quality Checklist
Required
idris2 --buildemits zero warningsbelieve_me/postulate/sorry/assert_total) — proof is genuineAs Applicable
Testing
Verified with Idris2 0.7.0:
cd src/interface/abi && idris2 --build dafniser-abi.ipkg→ exit 0, zero warnings (all modules). Adversarial check: a deliberately-false proof was rejected by the type checker (non-vacuity).build/removed (not committed).🤖 Generated with Claude Code
https://claude.ai/code/session_01A6PSzJWpRxtzGDjUCEh7Mx
Generated by Claude Code