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.
31 lines
1.5 KiB
Plaintext
31 lines
1.5 KiB
Plaintext
(module loop_in_lambda_e2e
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(fn apply
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(doc "apply a fn-of-Int to an Int. Iter it.2: the supplied closure is loop-bearing, so its arrow carries !Diverge — the higher-order param type and apply's own effect row must reflect that (effects are part of the function type).")
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(type (fn-type (params (fn-type (params (con Int)) (ret (con Int)) (effects Diverge)) (con Int)) (ret (con Int)) (effects Diverge)))
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(params f x)
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(body (app f x)))
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(fn main
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(doc "Iter it.1 — a loop inside a lambda body, invoked via a closure. The lambda computes x*x by summing x exactly x times through an accumulator loop; apply 7 prints 49. Codegen-soundness gate for the lambda-boundary loop_frames save/restore. Iter it.2: !Diverge propagates out through apply (callee-effect propagation).")
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(type (fn-type (params) (ret (con Unit)) (effects IO Diverge)))
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(params)
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(body
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(app print
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(app apply
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; Iter it.2: the loop lives in THIS lambda's body, so the
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; lambda's arrow carries !Diverge (DD-4 lam boundary). The
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; loop does not leak Diverge to `main` — `main`'s body does
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; not syntactically contain the loop (it stops at the lam
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; edge, exactly as !IO does).
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(lam
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(params (typed x (con Int)))
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(ret (con Int))
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(effects Diverge)
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(body
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(loop ((var acc (con Int) 0) (var k (con Int) 0))
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(if (app == k x)
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acc
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(recur (app + acc x) (app + k 1))))))
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7)))))
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