Brummel
a4be1e58a3
Iteration-discipline milestone, 2 of 3. Strictly additive (nothing tail-related removed; that is it.3). New whole-body pass verify_structural_recursion sibling of verify_tail_positions (DD-1): smaller-set algorithm with implicit candidate inference + unconstrained accumulators (DD-2, foldl=structural), self/mutual via inline ADT-family union-find (DD-3), it.2-only tail==false grandfather. CheckError::NonStructuralRecursion. term_contains_loop (stops at Term::Lam, DD-4) injects Diverge so existing UndeclaredEffect enforces it, no new variant; lam-arrow + LetRec sub-effect sites wired. DESIGN.md Decision 3 synced. Four it.1 loop fixtures gained !Diverge. Two spec-premise boundary defects surfaced + resolved within the additive invariant (corpus clean, check not weakened), recorded as corrected it.3 corpus-migration scope: (1) the "21 tail-app fixtures" grandfather premise under-counts the corpus — no-ADT-candidate counter recursions have no structural position to verify, deferred to it.3; (2) two RC-regression fixtures joined the spec's transitional tail-app grandfather as the other 20 do (RC==GC guards verified still green). cargo test --workspace 622/0; 9 acceptance pins non-vacuous. Specfda9b78, planbc9f512.
27 lines
896 B
Plaintext
27 lines
896 B
Plaintext
; Iter it.2 positive (spec D1): foldl-shape accumulator. `go` recurses
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; on the Cons-tail `t` at position 0 (structurally guarded) while
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; threading an unconstrained accumulator `acc` at position 1. The
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; accumulator position is never examined by the guardedness check, so
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; this classifies as structural recursion: pure, total, Diverge-free,
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; with NO `tail-app` marker. This is the single most LLM-natural
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; iteration shape and must stay structural (spec D1).
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(module struct_rec_foldl_sum
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(data IntList
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(ctor INil)
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(ctor ICons (con Int) (con IntList)))
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(fn go
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(doc "Sum via a foldl-shape accumulator; structural on the tail.")
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(type
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(fn-type
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(params (con IntList) (con Int))
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(ret (con Int))))
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(params xs acc)
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(body
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(match xs
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(case (pat-ctor INil) acc)
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(case (pat-ctor ICons h t)
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(app go t (app + acc h)))))))
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