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Brummel 76b21c00eb feat(lang): eliminate the Implicit ownership default — totality + the drop-soundness it demasks (#55)
Deletes `ParamMode::Implicit`. `ParamMode` is now `{Own, Borrow}`:
every fn-type slot on every signature carries an explicit `own` or
`borrow`, no defaulted position survives anywhere (model 0008 §2,
spec 0062). The parser rejects a bare fn-type slot; `borrow-return`
and `borrow-over-value` reject at the signature; the corpus is
migrated to minimal-ownership modes (consumed ⇒ own, read-only-heap
⇒ borrow, value ⇒ trivial-own). The documented `Implicit`-ret-mode
leak is fixed: an owned heap return now drops exactly once (live=0,
acceptance criterion 5).

This was the easy half. Removing the default ACTIVATED a family of
drop paths that `Implicit` had silently skipped — the pre-cutover
language was leaking (and in places mis-dropping) here rather than
crashing, because an Implicit scrutinee turned the drop off. Making
the modes explicit (Own) turned those paths on and exposed two
latent-bug clusters, all fixed RED-first as part of this cutover:

Drop-soundness family (four legs):
  A. lit-sub-pattern double-free — the desugar re-matched the same
     owned scrutinee in the lit fall-through; fixed by grouping
     consecutive same-ctor arms into one match (bind fields once),
     in ailang-core desugar.
  B. Cons-husk leak on non-tail arm bodies — the lit-sub-pattern
     desugar rebound the owned scrutinee via `Let $mp = xs`, which
     bumped consume_count and suppressed the existing fn-return
     partial_drop. Fixed by not rebinding a bare-Var scrutinee
     (one husk-freeing mechanism, not two).
  C. polymorphic `drop_<T>` rc_dec'd monomorphised value fields —
     the per-ADT drop fn was emitted once from the polymorphic
     TypeDef, defaulting type-var fields to ptr and rc_dec'ing
     inline Ints (segfault). Fixed with per-monomorph drop
     functions (new ailang-codegen::dropmono): the drop set is
     collected from the lowered MIR, value-type fields are skipped,
     heap fields still freed once; monomorphic-concrete ADTs keep
     their byte-identical un-suffixed drop symbol.
  D. static Str literal passed to an `(own Str)` param — the
     literal lowers to a header-less rodata constant; the callee's
     now-active rc_dec read its length field as a refcount and
     freed a static address (segfault). Fixed with the missing
     fourth StrRep::Static→Heap promotion in lower_to_mir's App arm,
     gated on Own mode (borrow args stay static, no regression).

over-strict-mode lint over-fired: it suggested `(borrow V)` for
value-typed params (which `borrow-over-value` rejects — own is the
only legal mode there) and fired on `(intrinsic)` bodies (whose
consumption the linearity walk cannot observe). Tightened to skip
both; contract 0008 updated to the narrowed firing scope.

Irreversible step — canonical-form hash reset (model 0008 §6,
acceptance criterion 6). Every signature now carries explicit modes,
so the hashable canonical JSON changed for every module. RATIFY:
the corpus-wide hash-pin reset (hash_pin, prelude_module_hash_pin,
mono_hash_stability, eq_ord_e2e, embed_export_hash_stable, the
ct4/iter*/loop_recur schema-extension pins) and the list ir_snapshot
golden were regenerated once, deliberately, as the intended one-time
consequence of removing the mode elision from the canonical form —
not a regression. Each regenerated hash verified deterministic across
two runs.

Also fixes a pre-existing latent failure surfaced by the verification
gate, unrelated to this cutover: the `every_contract_names_a_resolvable_
ratifying_test` resolver (design_index_pin) could not resolve the
" + " dual-link ratifying-test form (`uniqueness.rs + linearity.rs`)
that the #57 audit-close (dfdc65f) introduced — it shipped red on that
commit. Resolver taught the dual-link form, mirroring its sibling.

Verification: cargo test --workspace = 731 passed, 0 failed (twice,
stable); e2e 102 passed, no binary exits non-zero (corpus crash-free);
grep-clean for Implicit/fn_implicit/mode_eq across crates; every drop
fix confirmed via emitted IR + AILANG_RC_STATS balance on the head==K,
head!=K, and Nil paths. Three BLOCKEDs en route (the unsound first
husk-dec attempt, the over-strict derivation premise, the leg-B fix
direction) were each treated as a real design/spec gap and rediagnosed,
not patched over.

Supersedes #54 (return-position-only leak patch). Precondition #57
(linearity hardening) was already met. Spec docs/specs/0062, plan
docs/plans/0121.

closes #55
2026-06-02 00:03:46 +02:00

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; Fieldtest raw-buf comprehensive .2 (Axes 1+2+3 — Bool element width
; through a fill loop, then counted via a borrow helper).
;
; Task an LLM author is naturally given: "mark which of the numbers
; 0..N are even in a flag buffer, then count how many flags are set."
; A flat Bool RawBuf is the natural storage for a flag/bitset array.
;
; The prior field test only stored a single Bool at a literal index
; (rawbuf_3_sensor_pair). This drives the i1/i8 Bool packing edge
; through a (loop ...)/recur FILL of runtime length N (one RawBuf.set
; per slot, the stored value being a *computed* Bool — the result of
; `eq (i % 2) 0`), and reads the flags back through a `borrow` helper
; (`count_set`) that drives off RawBuf.size and accumulates an Int.
;
; This stresses:
; - Bool stored/loaded across a loop, not a literal set — does the
; i1/i8 round-trip hold when the value is computed, not a `true`
; literal?
; - A borrow-receiver helper over a Bool buffer (the #46 fix on the
; Bool width).
; - `RawBuf.get` of a Bool used directly as an `if` condition inside
; the count loop.
;
; N = 6 -> flags for 0,1,2,3,4,5 -> even at 0,2,4 -> 3 set.
; Expected stdout: "3".
(module rbx_2_bool_sieve
(fn mark_even
(doc "Set slot i to (i is even) for i in 0..n. Linear own->own.")
(type (fn-type (params (own (con RawBuf (con Bool))) (own (con Int))) (ret (own (con RawBuf (con Bool))))))
(params buf n)
(body
(loop (b (con RawBuf (con Bool)) buf) (i (con Int) 0)
(if (app ge i n)
b
(recur (app RawBuf.set b i (app eq (app % i 2) 0))
(app + i 1))))))
(fn count_set
(doc "Count the set flags, reading the Bool buffer through a borrow.")
(type (fn-type (params (borrow (con RawBuf (con Bool)))) (ret (own (con Int)))))
(params buf)
(body
(loop (acc (con Int) 0) (i (con Int) 0)
(if (app ge i (app RawBuf.size buf))
acc
(recur (if (app RawBuf.get buf i) (app + acc 1) acc)
(app + i 1))))))
(fn main
(type (fn-type (params) (ret (own (con Unit))) (effects IO)))
(params)
(body
(let buf (new RawBuf (con Bool) 6)
(let buf (app mark_even buf 6)
(app print (app count_set buf)))))))