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.
88 lines
2.9 KiB
Plaintext
88 lines
2.9 KiB
Plaintext
; Iter 18g tidy follow-up RED-test fixture: a let-binder whose
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; value is a Term::Var referencing a non-Own fn-param must
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; inherit the param's mode for codegen's drop-emission gates.
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;
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; The carve-out documented in 18d.4's Iter A fix: the gate
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; checks `scrutinee_is_owned` against `current_param_modes`,
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; but only fn-params are recorded there. A let-binder aliasing
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; an Implicit-mode fn-param passes the gate (its lookup
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; misses, default = owned), so the arm-close drop fires on
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; memory the caller still references.
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;
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; Pattern: `pin_aliased` takes `t` as Implicit-mode (default,
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; no annotation); aliases it via `(let a t ...)`; matches `a`.
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; In the TNode arm the pattern-bindings `l` / `r` would be
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; dec'd at arm close because `a` looks owned to the gate —
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; corrupting the caller's tree.
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;
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; Pre-fix under --alloc=rc: refcount underflow at the second
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; iteration of `loop`, where the recursive call into
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; `pin_aliased(t)` re-loads cells the previous iteration
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; freed.
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; Post-fix: clean exit, output `0`. Stats are not the focus
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; here (the caller's tree leaks under the Implicit-mode
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; back-compat lane); the test asserts only correctness.
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(module rc_let_alias_implicit_param
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(data Tree
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(ctor TLeaf)
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(ctor TNode (con Int) (con Tree) (con Tree)))
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(fn build
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(type
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(fn-type
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(params (con Int))
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(ret (own (con Tree)))))
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(params d)
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(body
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(if (app == d 0)
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(term-ctor Tree TLeaf)
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(term-ctor Tree TNode 1
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(app build (app - d 1))
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(app build (app - d 1))))))
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; Pin via let-alias: the alias `a` is a Var-binding on the
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; Implicit-mode (default) param `t`. Codegen's gate must
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; recognise that `a` inherits `t`'s mode and skip the arm-
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; close drop that would otherwise fragment the caller's
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; tree.
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(fn pin_aliased
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(type
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(fn-type
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(params (con Tree))
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(ret (con Int))))
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(params t)
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(body
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(let a t
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(match a
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(case (pat-ctor TLeaf) 0)
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(case (pat-ctor TNode v l r) 1)))))
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; Iter it.2: integer-counter recursion holding the ADT param `t`
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; constant — non-structural by the it.2 guardedness check (D2). The
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; recursive call is in tail position, so it joins the transitional
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; `tail-app` grandfather (spec it.2 "Transitional grandfather") as
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; the rest of the corpus does until it.3 migrates such recursions
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; to `(loop …)`. The 18g let-alias-mode regression this fixture
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; guards lives in `pin_aliased`'s match arm-close, unaffected by
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; this tail marking.
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(fn loop
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(type
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(fn-type
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(params (con Int) (con Tree))
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(ret (con Int))))
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(params n t)
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(body
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(if (app == n 0)
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0
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(let _v (app pin_aliased t)
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(tail-app loop (app - n 1) t)))))
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(fn main
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(type (fn-type (params) (ret (con Unit)) (effects IO)))
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(params)
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(body
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(let t (app build 2)
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(app print (app loop 3 t))))))
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