Brummel
76b21c00eb
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
48 lines
2.1 KiB
Plaintext
48 lines
2.1 KiB
Plaintext
; RED fixture (refs #55, Implicit-cutover double-drop).
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;
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; Property under test: a ctor arm with a literal sub-pattern in a
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; non-tail field — `(Cons (pat-lit K) _)` — must drop the matched
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; value's owned children EXACTLY ONCE on the head!=K path.
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;
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; The 16c lit-sub-pattern desugar (crates/ailang-core/src/desugar.rs
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; `desugar_one_arm` / `wrap_sub`) lowers `(Cons (pat-lit K) _)` into an
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; outer Cons-match that binds the Cons fields, then an
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; `if (== head K) body else fall_k`. `fall_k` is the rest of the arm
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; chain, which RE-MATCHES the same owned scrutinee (re-binding its
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; children). Once the param mode is `Own` (post-#55 cutover, was
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; `Implicit`), the arm-close Iter-A drop in
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; crates/ailang-codegen/src/match_lower.rs (gated on
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; `scrutinee_is_owned`) fires on the tail child in BOTH the re-match arm
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; AND the enclosing lit-arm's join — the same heap pointer (`arg_xs+16`)
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; is dropped twice → double-free → SIGSEGV on the head!=K path.
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;
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; Pre-cutover this leaked instead of crashing (Implicit suppressed the
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; drop entirely). The fixture pins single-drop, not merely exit-0:
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; `cat` consumes its owned IntList arg, so a leak-free run frees every
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; cell exactly once. `main` drives both the head==K (0) and head!=K (7)
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; paths so the regression is visible on whichever path the fix touches.
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(module lit_pat_ctor_tail_drop
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(data IntList
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(ctor Nil)
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(ctor Cons (con Int) (con IntList)))
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(fn cat
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(doc "Empty -> -1; first element 0 -> 0; otherwise the head.")
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(type (fn-type (params (borrow (con IntList))) (ret (own (con Int)))))
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(params xs)
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(body
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(match xs
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(case (pat-ctor Nil) -1)
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(case (pat-ctor Cons (pat-lit 0) _) 0)
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(case (pat-ctor Cons h _) h))))
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(fn main
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(doc "Drive head==0 then head!=0. Expected (per line): 0, 7.")
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(type (fn-type (params) (ret (own (con Unit))) (effects IO)))
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(params)
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(body
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(seq (seq (app print (app cat (term-ctor IntList Cons 0 (term-ctor IntList Nil)))) (do io/print_str "\n"))
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(seq (app print (app cat (term-ctor IntList Cons 7 (term-ctor IntList Nil)))) (do io/print_str "\n"))))))
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