diff --git a/docs/plans/0120-harden-ownership-analysis.md b/docs/plans/0120-harden-ownership-analysis.md new file mode 100644 index 0000000..9b9842c --- /dev/null +++ b/docs/plans/0120-harden-ownership-analysis.md @@ -0,0 +1,752 @@ +# Harden the ownership analysis for universal activation — Implementation Plan + +> **Parent spec:** `docs/specs/0063-harden-ownership-analysis.md` +> +> **For agentic workers:** REQUIRED SUB-SKILL: use the +> `implement` skill to run this plan. Steps use `- [ ]` +> checkboxes for tracking. + +**Goal:** Make the linearity analysis (`crates/ailang-check/src/linearity.rs`) correct under universal activation by exempting value-type binders from consume-tracking and treating function application as a borrow, plus a new `is_value_type` predicate. + +**Architecture:** Two orthogonal additive changes inside `linearity.rs` (a value-type exemption gated on a per-binder `is_value` flag, and switching the `Term::App` callee walk from `Consume` to `Borrow`), plus one new shared predicate in `ailang-core::primitives`. No schema change, no hash reset, no codegen change. The analysis stays a pure diagnostic pass; the two existing diagnostic codes simply fire on a smaller, more correct set. + +**Tech Stack:** `ailang-core` (primitives predicate), `ailang-check` (linearity pass + in-source unit tests + on-disk fixture tests), `examples/` (`.ail` fixtures). + +--- + +**Files this plan creates or modifies:** + +- Modify: `crates/ailang-core/src/primitives.rs` — add `is_value_type`; extend the `#[cfg(test)] mod tests` block. +- Modify: `crates/ailang-check/src/linearity.rs` — `BinderState.is_value`; `Checker.ctors`; `type_is_value` + `collect_value_pattern_binders` helpers; param/pattern/lam seeding; `use_var` short-circuit; `Term::App` callee borrow; `merge_states` carry; in-source tests. +- Create: `examples/fp_value.ail` — Class-1 value-type RED→GREEN fixture. +- Create: `examples/fp_hof.ail` — Class-2a own-fn-param RED→GREEN fixture. +- Create: `examples/fp_map.ail` — Class-2b borrow-fn-param RED→GREEN fixture. +- Create: `examples/real_consume.ail` — must-stay-RED heap double-consume fixture. +- Modify: `crates/ailang-check/tests/workspace.rs` — on-disk linearity assertions for the four fixtures. + +--- + +## Task 1: `is_value_type` predicate + +**Files:** +- Modify: `crates/ailang-core/src/primitives.rs` + +- [ ] **Step 1: Write the failing test** + +In `crates/ailang-core/src/primitives.rs`, inside the existing `#[cfg(test)] mod tests` block, add this test after `predicate_and_surface_name_agree`: + +```rust + /// `is_value_type` is the unboxed/no-RC subset of the primitives: + /// it agrees with `is_primitive_name` on every name EXCEPT `Str`, + /// which is a primitive zero-arity ctor but is heap-allocated + /// (`ptr`, RC'd) — see drop.rs:490-492. + #[test] + fn value_type_is_primitive_minus_str() { + for name in ["Int", "Bool", "Float", "Unit"] { + assert!(is_value_type(name), "{name} must be a value type"); + assert!(is_primitive_name(name), "{name} must be a primitive"); + } + // The sole divergence: Str is a primitive but NOT a value type. + assert!(!is_value_type("Str"), "Str is heap-allocated, not a value type"); + assert!(is_primitive_name("Str"), "Str is still a primitive zero-arity ctor"); + // Non-primitives are neither. + for name in ["List", "Foo", ""] { + assert!(!is_value_type(name)); + assert!(!is_primitive_name(name)); + } + } +``` + +- [ ] **Step 2: Run test to verify it fails** + +Run: `cargo test -p ailang-core value_type_is_primitive_minus_str` +Expected: FAIL to compile — `cannot find function `is_value_type` in this scope`. + +- [ ] **Step 3: Write minimal implementation** + +In `crates/ailang-core/src/primitives.rs`, immediately after the closing `}` of `pub fn is_primitive_name`, insert: + +```rust +/// Returns `true` iff `name` is an **unboxed value type** — no RC, no +/// heap slab, copied by value. This is the `Str`-excluding subset of +/// [`is_primitive_name`]: `Str` is a primitive zero-arity ctor but is +/// heap-allocated (`ptr`, RC-`dec`'d — codegen `drop.rs:490-492` lowers +/// only `Int`/`Bool`/`Float`/`Unit` to non-`ptr`). Used by the +/// linearity analysis to exempt value-type binders from +/// consume-tracking: a value type is never consumed, so multi-use is +/// always legal. +pub fn is_value_type(name: &str) -> bool { + matches!(name, "Int" | "Bool" | "Float" | "Unit") +} +``` + +- [ ] **Step 4: Run test to verify it passes** + +Run: `cargo test -p ailang-core value_type_is_primitive_minus_str` +Expected: PASS. + +--- + +## Task 2: Application is a borrow + +**Files:** +- Modify: `crates/ailang-check/src/linearity.rs` (`Term::App` arm at `:430-433`; in-source tests) + +- [ ] **Step 1: Write the failing test** + +In `crates/ailang-check/src/linearity.rs`, inside `#[cfg(test)] mod tests`, add a helper (after `fn_with_modes`, near `:1315`) and a test. The helper builds a fn with a single function-typed param `p0 : (mode (Int -> Int))` returning Int: + +```rust + /// A fn with one function-typed param `p0 : (mode (Int -> Int))`, + /// returning Int. Used to exercise HOF application linearity. + fn fn_with_fn_param(name: &str, mode: ParamMode, body: Term) -> Def { + Def::Fn(FnDef { + name: name.into(), + ty: Type::Fn { + params: vec![Type::Fn { + params: vec![Type::int()], + param_modes: vec![ParamMode::Own], + ret: Box::new(Type::int()), + ret_mode: ParamMode::Own, + effects: vec![], + }], + param_modes: vec![mode], + ret: Box::new(Type::int()), + ret_mode: ParamMode::Implicit, + effects: vec![], + }, + params: vec!["p0".into()], + body, + suppress: vec![], + doc: None, + export: None, + }) + } + + /// Applying a function param more than once is a borrow each time, + /// not a consume: `(app p0 (app p0 0))` must NOT fire + /// use-after-consume. (Today the App callee is walked Consume, so + /// the first application consumes `p0` and the second fires + /// use-after-consume — this test is RED until Fix 2.) + #[test] + fn own_fn_param_applied_twice_is_clean() { + let body = Term::App { + callee: Box::new(Term::Var { name: "p0".into() }), + args: vec![Term::App { + callee: Box::new(Term::Var { name: "p0".into() }), + args: vec![Term::Lit { lit: Literal::Int { value: 0 } }], + tail: false, + }], + tail: false, + }; + let m = Module { + schema: ailang_core::SCHEMA.into(), + name: "t".into(), + kernel: false, + imports: vec![], + defs: vec![fn_with_fn_param("f", ParamMode::Own, body)], + }; + let diags = check_module(&m); + assert!( + !diags.iter().any(|d| d.code == "use-after-consume"), + "applying a function param is a borrow, not a consume; got {diags:?}" + ); + } +``` + +- [ ] **Step 2: Run test to verify it fails** + +Run: `cargo test -p ailang-check own_fn_param_applied_twice_is_clean` +Expected: FAIL — assertion fires; a `use-after-consume` diagnostic is present (the App callee is walked in `Position::Consume` today). + +- [ ] **Step 3: Write minimal implementation** + +In `crates/ailang-check/src/linearity.rs`, in the `Term::App { callee, args, .. }` arm (`:430-433`), change the callee walk. Replace: + +```rust + Term::App { callee, args, .. } => { + // The callee itself is consumed (it's "the function value"); + // for var-callees this is typically a global fn ref. + self.walk(callee, Position::Consume); +``` + +with: + +```rust + Term::App { callee, args, .. } => { + // Applying a function value READS it (a borrow): the value + // stays live for further applications and is dropped at + // scope close like any other binder. For a global fn-ref + // callee this is a no-op (globals are untracked, so + // `use_var` returns early either way); for a tracked + // function-typed binder (a HOF param) it stops application + // from consuming the binder. The `consumed` check still + // runs in Borrow position, so applying an already-consumed + // function value still fires use-after-consume. + self.walk(callee, Position::Borrow); +``` + +- [ ] **Step 4: Run test to verify it passes** + +Run: `cargo test -p ailang-check own_fn_param_applied_twice_is_clean` +Expected: PASS. + +--- + +## Task 3: Value-type exemption + +**Files:** +- Modify: `crates/ailang-check/src/linearity.rs` (`BinderState` `:181-192`; `Checker` `:408-420`; `Checker` literal `:351-356`; param install `:361-370`; `walk_arm` `:638-652`; `Term::Lam` `:541-560`; `use_var` `:683-690`; `merge_states` `:781-787`; new helpers; in-source tests) + +- [ ] **Step 1: Write the failing tests** + +In `crates/ailang-check/src/linearity.rs`, inside `#[cfg(test)] mod tests`, add a helper and three tests: + +```rust + /// A fn with one `(own (con Int))` value-type param `p0`, returning + /// Int. Used to exercise the value-type exemption. + fn fn_with_int_own(name: &str, body: Term) -> Def { + Def::Fn(FnDef { + name: name.into(), + ty: Type::Fn { + params: vec![Type::Con { name: "Int".into(), args: vec![] }], + param_modes: vec![ParamMode::Own], + ret: Box::new(Type::int()), + ret_mode: ParamMode::Implicit, + effects: vec![], + }, + params: vec!["p0".into()], + body, + suppress: vec![], + doc: None, + export: None, + }) + } + + /// A value-type param read in two consume positions + /// (`(seq p0 p0)`) must NOT fire use-after-consume: an `Int` has no + /// refcount and is never consumed. RED until Fix 1. + #[test] + fn value_param_multi_read_is_clean() { + let body = Term::Seq { + lhs: Box::new(Term::Var { name: "p0".into() }), + rhs: Box::new(Term::Var { name: "p0".into() }), + }; + let m = Module { + schema: ailang_core::SCHEMA.into(), + name: "t".into(), + kernel: false, + imports: vec![], + defs: vec![fn_with_int_own("f", body)], + }; + let diags = check_module(&m); + assert!( + !diags.iter().any(|d| d.code == "use-after-consume"), + "a value-type param is never consumed; multi-read is legal; got {diags:?}" + ); + } + + /// Type-gating guard: a HEAP param (`List`) consumed twice in a ctor + /// (`(term-ctor Pair Pair p0 p0)`) MUST still fire use-after-consume + /// after the fix — the exemption is value-type-only, not blanket. + /// (Green today and after the fix; a regression guard, not RED-first.) + #[test] + fn heap_param_multi_consume_still_errors() { + let body = Term::Ctor { + type_name: "Pair".into(), + ctor: "Pair".into(), + args: vec![ + Term::Var { name: "p0".into() }, + Term::Var { name: "p0".into() }, + ], + }; + let m = Module { + schema: ailang_core::SCHEMA.into(), + name: "t".into(), + kernel: false, + imports: vec![], + defs: vec![fn_with_modes("f", vec![ParamMode::Own], body)], + }; + let diags = check_module(&m); + assert!( + diags.iter().any(|d| d.code == "use-after-consume"), + "a heap param consumed twice must still error; got {diags:?}" + ); + } + + /// A borrow function param applied AND passed (the recursive-HOF + /// shape `map_int`) must be clean: application is a borrow, and the + /// param starts borrowed, so neither use-after-consume nor + /// consume-while-borrowed should fire. Covered by Fix 2 (App + /// borrow); this asserts the borrow-param variant. RED until Fix 2. + #[test] + fn borrow_fn_param_applied_is_clean() { + let body = Term::App { + callee: Box::new(Term::Var { name: "p0".into() }), + args: vec![Term::Lit { lit: Literal::Int { value: 0 } }], + tail: false, + }; + let m = Module { + schema: ailang_core::SCHEMA.into(), + name: "t".into(), + kernel: false, + imports: vec![], + defs: vec![fn_with_fn_param("f", ParamMode::Borrow, body)], + }; + let diags = check_module(&m); + assert!( + !diags.iter().any(|d| { + d.code == "use-after-consume" || d.code == "consume-while-borrowed" + }), + "applying a borrow function param is a clean read; got {diags:?}" + ); + } +``` + +- [ ] **Step 2: Run tests to verify they fail (the RED ones) / pass (the guard)** + +Run: `cargo test -p ailang-check value_param_multi_read_is_clean heap_param_multi_consume_still_errors borrow_fn_param_applied_is_clean` +Expected: `value_param_multi_read_is_clean` FAILS (use-after-consume fires today); `borrow_fn_param_applied_is_clean` PASSES (already fixed by Task 2's App-borrow change); `heap_param_multi_consume_still_errors` PASSES (regression guard, green today). + +- [ ] **Step 3a: Add the `is_value` field to `BinderState`** + +Replace the `BinderState` struct (`:181-192`): + +```rust +#[derive(Debug, Default, Clone)] +struct BinderState { + /// `true` once the binder has been used in a Consume position. + /// Subsequent uses (in any position) trigger `use-after-consume`. + consumed: bool, + /// Number of currently-live borrows of this binder. ... + borrow_count: u32, +} +``` + +with (keep the existing doc comments on `consumed`/`borrow_count` verbatim; only the field is added): + +```rust +#[derive(Debug, Default, Clone)] +struct BinderState { + /// `true` once the binder has been used in a Consume position. + /// Subsequent uses (in any position) trigger `use-after-consume`. + consumed: bool, + /// Number of currently-live borrows of this binder. Incremented + /// when a Borrow-position use starts (in a fn-call arg slot or as + /// the initial state of a `Borrow` parameter); decremented when + /// the borrow ends. Consume while `> 0` triggers + /// `consume-while-borrowed`. + borrow_count: u32, + /// `true` if this binder has an unboxed value type + /// (`Int`/`Bool`/`Float`/`Unit`). A value type has no refcount and + /// is never consumed, so `use_var` skips all consume bookkeeping + /// for it. Invariant per binder; set at the introduction site + /// (param / pattern / lam) where the type is locally available. + is_value: bool, +} +``` + +- [ ] **Step 3b: Add the type-is-value helper** + +In `crates/ailang-check/src/linearity.rs`, immediately after the `is_heap_type` function (`:164`), add: + +```rust +/// `true` iff `t` is an unboxed value type (`Int`/`Bool`/`Float`/`Unit`). +/// The `Str`-excluding counterpart of `is_heap_type`'s primitive check — +/// see `ailang_core::primitives::is_value_type`. +fn type_is_value(t: &Type) -> bool { + matches!(t, Type::Con { name, .. } if ailang_core::primitives::is_value_type(name)) +} +``` + +- [ ] **Step 3c: Add the `ctors` field to `Checker` and the value-binder pattern helper** + +Replace the `Checker` struct field list (`:408-420`) — add the `ctors` field after `def_name`: + +```rust +struct Checker<'a> { + /// Top-level symbol → type. Used to look up the param_modes of an + /// `App` callee that resolves to a global fn def. + globals: &'a HashMap, + /// Diagnostic accumulator (shared with the module-level walk). + diags: &'a mut Vec, + /// Name of the fn currently being checked (becomes + /// [`Diagnostic::def`]). + def_name: &'a str, + /// ctor name → field types. Used to type pattern binders so a + /// value-typed sub-binder (`Cons(h, t)` with `h: Int`) is exempted + /// from consume-tracking. Mirrors the `ctors` map built in + /// `check_module_with_visible`. + ctors: &'a HashMap>, + /// Live binder state, keyed by name. Modified in place; lexical + /// scoping is restored by [`Checker::with_binder`]. + binders: HashMap, +} +``` + +Then add this free function after `collect_pattern_binders` (`:775`): + +```rust +/// Collect the names of pattern binders that have an unboxed value +/// type, by walking the pattern alongside the ctor field types. +/// Mirrors `pattern_has_consumed_heap_binder_at`'s descent: a +/// `Pattern::Var` directly under a ctor field of value type is added; +/// a top-level `Pattern::Var` (whole-scrutinee binder, `declared_ty == +/// None`) is conservatively treated as heap and never added. +fn collect_value_pattern_binders( + pat: &Pattern, + declared_ty: Option<&Type>, + ctors: &HashMap>, + out: &mut Vec, +) { + match pat { + Pattern::Wild | Pattern::Lit { .. } => {} + Pattern::Var { name } => { + if let Some(t) = declared_ty { + if type_is_value(t) { + out.push(name.clone()); + } + } + } + Pattern::Ctor { ctor, fields } => { + let field_tys: &[Type] = ctors.get(ctor).map(|v| v.as_slice()).unwrap_or(&[]); + for (i, f) in fields.iter().enumerate() { + collect_value_pattern_binders(f, field_tys.get(i), ctors, out); + } + } + } +} +``` + +- [ ] **Step 3d: Wire `ctors` into the `Checker` literal and seed param `is_value`** + +Replace the `Checker` construction + param install loop in `check_fn` (`:351-370`): + +```rust + let mut checker = Checker { + globals, + diags, + def_name: &f.name, + binders: HashMap::new(), + }; + + // Install fn parameters as binders, with initial `borrow_count = 1` + // for `Borrow` params (the caller's outer borrow stays live for the + // body's whole duration) and `0` for `Own` params. + for (name, mode) in f.params.iter().zip(param_modes.iter()) { + let initial = BinderState { + consumed: false, + borrow_count: match mode { + ParamMode::Borrow => 1, + ParamMode::Own | ParamMode::Implicit => 0, + }, + }; + checker.binders.insert(name.clone(), initial); + } +``` + +with: + +```rust + let mut checker = Checker { + globals, + diags, + def_name: &f.name, + ctors, + binders: HashMap::new(), + }; + + // Install fn parameters as binders, with initial `borrow_count = 1` + // for `Borrow` params (the caller's outer borrow stays live for the + // body's whole duration) and `0` for `Own` params. A value-type + // param starts `is_value = true` and is exempt from consume-tracking. + for (i, (name, mode)) in f.params.iter().zip(param_modes.iter()).enumerate() { + let initial = BinderState { + consumed: false, + borrow_count: match mode { + ParamMode::Borrow => 1, + ParamMode::Own | ParamMode::Implicit => 0, + }, + is_value: param_tys.get(i).map(type_is_value).unwrap_or(false), + }; + checker.binders.insert(name.clone(), initial); + } +``` + +- [ ] **Step 3e: Seed `is_value` for pattern binders in `walk_arm`** + +Replace the binder-install loop in `walk_arm` (`:638-644`): + +```rust + fn walk_arm(&mut self, arm: &Arm, pos: Position) { + let names = collect_pattern_binders(&arm.pat); + let mut saved: HashMap> = HashMap::new(); + for n in &names { + saved.insert(n.clone(), self.binders.remove(n)); + self.binders.insert(n.clone(), BinderState::default()); + } +``` + +with: + +```rust + fn walk_arm(&mut self, arm: &Arm, pos: Position) { + let names = collect_pattern_binders(&arm.pat); + let mut value_names: Vec = Vec::new(); + collect_value_pattern_binders(&arm.pat, None, self.ctors, &mut value_names); + let mut saved: HashMap> = HashMap::new(); + for n in &names { + saved.insert(n.clone(), self.binders.remove(n)); + let st = BinderState { + is_value: value_names.contains(n), + ..BinderState::default() + }; + self.binders.insert(n.clone(), st); + } +``` + +- [ ] **Step 3f: Seed `is_value` for lam params in `Term::Lam`** + +Replace the `Term::Lam` arm's destructure and param-install loop (`:541-552`): + +```rust + Term::Lam { params, body, .. } => { + // Lam captures cross the linearity boundary: any free + // var of the body is implicitly consumed by closure + // construction (we don't yet model captured-borrow + // discipline; that is 18c.3 territory). For 18c.2 we + // walk the body with the lam's own params as fresh + // binders. + let mut saved_for_params: HashMap> = HashMap::new(); + for p in params { + saved_for_params.insert(p.clone(), self.binders.remove(p)); + self.binders.insert(p.clone(), BinderState::default()); + } +``` + +with: + +```rust + Term::Lam { params, param_tys, body, .. } => { + // Lam captures cross the linearity boundary: any free + // var of the body is implicitly consumed by closure + // construction (we don't yet model captured-borrow + // discipline; that is 18c.3 territory). For 18c.2 we + // walk the body with the lam's own params as fresh + // binders; a value-typed lam param is exempt from + // consume-tracking. + let mut saved_for_params: HashMap> = HashMap::new(); + for (i, p) in params.iter().enumerate() { + saved_for_params.insert(p.clone(), self.binders.remove(p)); + let st = BinderState { + is_value: param_tys.get(i).map(type_is_value).unwrap_or(false), + ..BinderState::default() + }; + self.binders.insert(p.clone(), st); + } +``` + +- [ ] **Step 3g: Short-circuit the consume arm in `use_var`** + +Replace the `Position::Consume` arm in `use_var` (`:683-690`): + +```rust + Position::Consume => { + if state.borrow_count > 0 { + self.diags + .push(make_consume_while_borrowed(self.def_name, name)); + return; + } + state.consumed = true; + } +``` + +with: + +```rust + Position::Consume => { + // A value type has no refcount and is never consumed; + // multi-use in any position is legal. + if state.is_value { + return; + } + if state.borrow_count > 0 { + self.diags + .push(make_consume_while_borrowed(self.def_name, name)); + return; + } + state.consumed = true; + } +``` + +- [ ] **Step 3h: Carry `is_value` through `merge_states`** + +Replace `merge_states` (`:781-787`): + +```rust +fn merge_states(into: &mut HashMap, other: &HashMap) { + for (name, s) in other { + let entry = into.entry(name.clone()).or_default(); + entry.consumed = entry.consumed || s.consumed; + entry.borrow_count = entry.borrow_count.max(s.borrow_count); + } +} +``` + +with (add the `is_value` carry — invariant per binder, but `or_default()` would otherwise reset a value binder present only in `other` to `false`): + +```rust +fn merge_states(into: &mut HashMap, other: &HashMap) { + for (name, s) in other { + let entry = into.entry(name.clone()).or_default(); + entry.consumed = entry.consumed || s.consumed; + entry.borrow_count = entry.borrow_count.max(s.borrow_count); + // is_value is invariant per binder; the OR recovers it when the + // binder reached `into` via a fresh `or_default()`. + entry.is_value = entry.is_value || s.is_value; + } +} +``` + +- [ ] **Step 4: Build and run the linearity tests** + +Run: `cargo build -p ailang-check` +Expected: 0 errors (every `BinderState` / `Checker` literal compiles; the `..Default::default()` tail and the explicit `is_value` field cover all sites). + +Run: `cargo test -p ailang-check value_param_multi_read_is_clean heap_param_multi_consume_still_errors borrow_fn_param_applied_is_clean own_fn_param_applied_twice_is_clean` +Expected: all PASS. + +--- + +## Task 4: On-disk fixtures and assertions + +**Files:** +- Create: `examples/fp_value.ail`, `examples/fp_hof.ail`, `examples/fp_map.ail`, `examples/real_consume.ail` +- Modify: `crates/ailang-check/tests/workspace.rs` + +- [ ] **Step 1: Create the four fixtures** + +Create `examples/fp_value.ail`: + +```ail +(module fp_value + (fn sum_explicit + (doc "value-type param read multiple times") + (type (fn-type (params (own (con Int))) (ret (own (con Int))))) + (params n) + (body (if (app eq n 0) 0 (app + n (app sum_explicit (app - n 1)))))) + (fn main + (type (fn-type (params) (ret (own (con Unit))) (effects IO))) + (params) + (body (app print (app sum_explicit 10))))) +``` + +Create `examples/fp_hof.ail`: + +```ail +(module fp_hof + (fn apply_thrice + (doc "apply a function param three times") + (type (fn-type + (params (own (fn-type (params (own (con Int))) (ret (own (con Int))))) (own (con Int))) + (ret (own (con Int))))) + (params f x) + (body (app f (app f (app f x))))) + (fn main + (type (fn-type (params) (ret (own (con Unit))) (effects IO))) + (params) + (body (app print (app apply_thrice (lam (params (typed y (con Int))) (ret (con Int)) (body (app + y 1))) 0))))) +``` + +Create `examples/fp_map.ail`: + +```ail +(module fp_map + (data IntList + (doc "boxed list") + (ctor Nil) + (ctor Cons (con Int) (con IntList))) + (fn map_int + (doc "recursive HOF: f applied AND passed to the recursive call") + (type (fn-type + (params (borrow (fn-type (params (own (con Int))) (ret (own (con Int))))) (own (con IntList))) + (ret (own (con IntList))))) + (params f xs) + (body (match xs + (case (pat-ctor Nil) (term-ctor IntList Nil)) + (case (pat-ctor Cons h t) (term-ctor IntList Cons (app f h) (app map_int f t))))))) +``` + +Create `examples/real_consume.ail`: + +```ail +(module real_consume + (data Box + (doc "heap cell") + (ctor Box (con Int))) + (data Pair + (doc "two boxes") + (ctor Pair (con Box) (con Box))) + (fn dup + (doc "MUST STAY an error: a heap param consumed twice without clone") + (type (fn-type (params (own (con Box))) (ret (own (con Pair))))) + (params b) + (body (term-ctor Pair Pair b b)))) +``` + +- [ ] **Step 2: Verify the fixtures check clean / error as designed** + +Run: `cargo build -p ail && for f in fp_value fp_hof fp_map real_consume; do echo "== $f =="; ./target/debug/ail check examples/$f.ail; echo "exit=$?"; done` +Expected: `fp_value`, `fp_hof`, `fp_map` each exit 0 (clean, post-fix); `real_consume` exits 1 with `[use-after-consume] dup: \`b\` is used after it was already consumed`. + +- [ ] **Step 3: Add the on-disk assertions** + +In `crates/ailang-check/tests/workspace.rs`, append after `borrow_own_demo_is_linearity_clean` (`:720`): + +```rust +/// #56 Fix 1+2: under universal activation the linearity analysis must +/// not false-fire on value-type params or on applied function params. +/// These three fixtures use explicit-mode signatures (so the analysis +/// is active today) and were RED before the hardening (docs/specs/0063). +#[test] +fn harden_ownership_false_positives_are_clean() { + for name in ["fp_value", "fp_hof", "fp_map"] { + let entry = examples_dir().join(format!("{name}.ail")); + let ws = load_workspace(&entry).unwrap_or_else(|e| panic!("load {name}: {e:?}")); + let diags = check_workspace(&ws); + let lin: Vec<&ailang_check::Diagnostic> = diags + .iter() + .filter(|d| d.code == "use-after-consume" || d.code == "consume-while-borrowed") + .collect(); + assert!(lin.is_empty(), "{name} must be linearity-clean; got: {lin:#?}"); + } +} + +/// #56 type-gating: the exemption is value-type-only. A heap param +/// consumed twice (`real_consume.dup`, `(term-ctor Pair Pair b b)`) MUST +/// still fire use-after-consume — proving the fix did not blanket-silence +/// genuine multi-consume. +#[test] +fn harden_ownership_heap_double_consume_still_errors() { + let entry = examples_dir().join("real_consume.ail"); + let ws = load_workspace(&entry).expect("load real_consume"); + let diags = check_workspace(&ws); + assert!( + diags.iter().any(|d| d.code == "use-after-consume"), + "real_consume.dup must still fire use-after-consume; got: {diags:#?}" + ); +} +``` + +- [ ] **Step 4: Run the on-disk assertions** + +Run: `cargo test -p ailang-check --test workspace harden_ownership` +Expected: both `harden_ownership_false_positives_are_clean` and `harden_ownership_heap_double_consume_still_errors` PASS. + +- [ ] **Step 5: Full workspace regression** + +Run: `cargo test --workspace` +Expected: PASS (no regressions; per the typed-MIR re-synth strictness memory, the whole suite is the net, not just e2e). + +Run: `python3 bench/check.py && python3 bench/compile_check.py` +Expected: both report clean (the analysis is diagnostic-only; no compile-baseline shift expected).