iter 24.tidy: close 5 actionable drift items from audit-24

Documents the three iter-24.3 strengthenings as load-bearing
invariants and tightens two error-handling sites:

T1: DESIGN.md gains new subsection §Cross-module references in
synthesised bodies (between Resolution-and-monomorphisation and
Defaults-and-superclasses) documenting three invariants installed
in iter 24.3 — (1) MonoTarget::FreeFn::type_args carries canonical
types post-collection via normalize_type_for_lookup; (2) post-mono
synthesised body cross-module refs may bypass the source template's
import_map (codegen falls back to module_user_fns / module_def_ail_types);
(3) FreeFnCall synth pushes one ResidualConstraint per declared
forall-constraint with rigid vars substituted by fresh metavars.

T2: codegen_import_map_fallback_pin.rs (integration test) asserts
the synthesised prelude.print__<IntBox> body references
show_user_adt.show__<IntBox> AND prelude module's imports do not
contain show_user_adt — proving the cross-module ref bypasses
import_map at codegen.

T3: polyfn_dot_qualified_branch_pin.rs (integration test) asserts
bare-name print f (f : Int -> Int) fires exactly one no-instance
diagnostic at typecheck with zero unknown-variable diagnostics —
proving the bare-name resolution reaches the dot-qualified synth
branch where the constraint-residual push fires.

T4: check/lib.rs:2858 unwrap_or_default() replaced with .expect()
carrying the registry-coherence message — class_methods index
drift now surfaces explicitly rather than rendering NoInstance
with an empty method name.

T5: mono.rs gains apply_subst_and_normalize helper (Option<Type>
return) extracted from two byte-identical call sites at
collect_mono_targets and collect_residuals_ordered. Each call site
retains its own rigid-var / unit-default policy in the None arm
(site 1: rigid → has_rigid+break, unbound → Type::unit; site 2:
non-concrete → Type::unit). Byte-identity invariant on mono-symbol
hashes enforced by construction.

Tests: 558 passed (was 556 + 2 new pins). No production semantic
change — pure documentation + test pin + error-handling tightening
+ helper refactor. bench/cross_lang exit 0; bench/compile_check +
bench/check exit 0 this run (latency.implicit_at_rc / latency.explicit_at_rc /
bench_list_sum.bump_s noise envelope unobserved, lineage continues
at 10th consecutive observation without firing this run).
This commit is contained in:
2026-05-13 04:28:15 +02:00
parent 0e27533e73
commit 4e8447d15d
7 changed files with 502 additions and 41 deletions
@@ -0,0 +1,19 @@
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@@ -0,0 +1,124 @@
//! Pin for the iter-24.3 codegen `import_map`-fallback path
//! (DESIGN.md §"Cross-module references in synthesised bodies"
//! invariant 2).
//!
//! Property protected: post-mono synthesised body cross-module
//! references resolve at codegen via the fallback to
//! `module_user_fns` / `module_def_ail_types` when the prefix is
//! NOT in the current module's `import_map`. Specifically, the
//! synthesised `prelude.print__<UserType>` body references
//! `<user_module>.show__<UserType>` even though `prelude` does not
//! import user modules.
//!
//! Failure mode this pin catches: a future codegen refactor
//! tightens `resolve_top_level_fn` or `lower_app`'s cross-module
//! arm or `synth_with_extras`'s Var arm back to `import_map`-only.
//! Without this pin, the regression surfaces only at the
//! `show_user_adt` E2E (which builds + runs a binary, slow to
//! bisect).
use ailang_check::{check_workspace, monomorphise_workspace};
use ailang_core::ast::{Def, Term};
use ailang_core::workspace::load_workspace;
use std::path::PathBuf;
fn fixture_path() -> PathBuf {
PathBuf::from(env!("CARGO_MANIFEST_DIR"))
.join("../../examples")
.join("show_user_adt.ail.json")
}
#[test]
fn synthesised_print_uses_user_module_show_via_fallback() {
// Step 1: workspace loads + typechecks clean.
let ws = load_workspace(&fixture_path()).expect("workspace loads");
let diags = check_workspace(&ws);
assert!(
diags.is_empty(),
"typecheck diagnostics in show_user_adt fixture: {diags:?}"
);
// Step 2: mono synthesis produces `prelude.print__<IntBox>` whose
// body references `show_user_adt.show__<IntBox>` (cross-module).
let post_mono = monomorphise_workspace(&ws).expect("mono green");
let prelude_mod = post_mono
.modules
.get("prelude")
.expect("prelude post-mono module present");
let print_def = prelude_mod
.defs
.iter()
.find_map(|d| match d {
Def::Fn(f) if f.name.starts_with("print__") => Some(f),
_ => None,
})
.expect("synthesised print__<UserType> not found in prelude post-mono module");
// Step 3: recursively walk `print_def.body` looking for a Var
// whose name carries the `show_user_adt.` prefix (the cross-
// module reference invariant 2 protects).
fn contains_xmod_show_var(t: &Term) -> bool {
match t {
Term::Var { name } => {
name.starts_with("show_user_adt.") && name.contains("show__")
}
Term::Let { value, body, .. } => {
contains_xmod_show_var(value) || contains_xmod_show_var(body)
}
Term::LetRec { body, in_term, .. } => {
contains_xmod_show_var(body) || contains_xmod_show_var(in_term)
}
Term::App { callee, args, .. } => {
contains_xmod_show_var(callee) || args.iter().any(contains_xmod_show_var)
}
Term::Do { args, .. } => args.iter().any(contains_xmod_show_var),
Term::Lam { body, .. } => contains_xmod_show_var(body),
Term::If { cond, then, else_ } => {
contains_xmod_show_var(cond)
|| contains_xmod_show_var(then)
|| contains_xmod_show_var(else_)
}
Term::Match { scrutinee, arms } => {
contains_xmod_show_var(scrutinee)
|| arms.iter().any(|a| contains_xmod_show_var(&a.body))
}
Term::Ctor { args, .. } => args.iter().any(contains_xmod_show_var),
Term::Seq { lhs, rhs } => {
contains_xmod_show_var(lhs) || contains_xmod_show_var(rhs)
}
Term::Clone { value } => contains_xmod_show_var(value),
Term::ReuseAs { source, body } => {
contains_xmod_show_var(source) || contains_xmod_show_var(body)
}
Term::Lit { .. } => false,
}
}
assert!(
contains_xmod_show_var(&print_def.body),
"synthesised print body should contain a `show_user_adt.<suffix>` Var \
referencing the user-module's show__<IntBox> mono symbol — \
this is the cross-module reference codegen resolves via the \
import_map-fallback path. Body: {:?}",
print_def.body
);
// Step 4: confirm prelude module's `imports` does NOT contain
// `show_user_adt` — the resolution at codegen time genuinely
// bypasses the source template's import_map.
let prelude_src = ws
.modules
.get("prelude")
.expect("prelude source module present");
assert!(
prelude_src
.imports
.iter()
.all(|imp| imp.module != "show_user_adt"),
"prelude must not import show_user_adt (the invariant is that \
codegen resolves the cross-module ref WITHOUT going through \
import_map). Got imports: {:?}",
prelude_src.imports
);
}
@@ -0,0 +1,71 @@
//! Pin for the iter-24.3 FreeFnCall constraint-residual-push
//! invariant (DESIGN.md §"Cross-module references in synthesised
//! bodies" invariant 3).
//!
//! Property protected: bare-name references to polymorphic free fns
//! that resolve through the auto-injected-prelude path AT THE
//! DOT-QUALIFIED SYNTH BRANCH push residuals for the fn's declared
//! constraints. The discharge loop then fires `NoInstance` at
//! typecheck if no instance ships for the unified concrete type.
//!
//! Failure mode this pin catches: a future refactor changes the
//! prelude auto-injection resolution path so that bare-name `print`
//! reaches synth via a different branch (e.g. locals, env.module_globals
//! direct hit) that does NOT push residuals. Without this pin, the
//! regression surfaces as `unknown variable: show` from codegen for
//! the negative case — confusing diagnostic, hard to bisect.
use ailang_check::check_workspace;
use ailang_core::workspace::load_workspace;
use std::path::PathBuf;
fn fixture_path() -> PathBuf {
PathBuf::from(env!("CARGO_MANIFEST_DIR"))
.join("../../examples")
.join("show_no_instance.ail.json")
}
#[test]
fn bare_name_polyfn_fires_typecheck_no_instance_not_codegen_unknown_var() {
// The fixture calls `print f` bare-name (no `prelude.` qualifier)
// where `f : Int -> Int`. The auto-injected-prelude resolution
// must route this through the dot-qualified synth branch so that
// the `Show a` declared constraint of `print` produces a residual,
// and the discharge loop fires `no-instance`.
let ws = load_workspace(&fixture_path()).expect("workspace loads");
let diags = check_workspace(&ws);
// Exactly one `no-instance` diagnostic — proves:
// (a) the bare-name `print` resolved (was not "unknown variable")
// (b) the resolution reached the dot-qualified synth branch
// which pushes the declared-constraint residual
// (c) the discharge loop ran with the residual and fired the
// NoInstance because no `Show (Int -> Int)` instance exists.
let no_inst: Vec<_> = diags.iter().filter(|d| d.code == "no-instance").collect();
assert_eq!(
no_inst.len(),
1,
"expected exactly one 'no-instance' diagnostic — got {} (all diags: {diags:?})",
no_inst.len()
);
// No "unknown variable" or other codegen-grade errors at typecheck:
// if the residual push did NOT fire, the typecheck would pass
// silently and the error would only surface at codegen.
let unknown_vars: Vec<_> = diags
.iter()
.filter(|d| {
d.code == "unknown-variable"
|| d.message.contains("unknown variable")
|| d.code == "internal"
})
.collect();
assert!(
unknown_vars.is_empty(),
"expected zero 'unknown variable' or 'internal' diagnostics at typecheck — \
got {} (all diags: {diags:?}). If this fires, the bare-name `print` \
resolution bypassed the dot-qualified synth branch and the constraint \
residual was never pushed.",
unknown_vars.len()
);
}
+8 -1
View File
@@ -2855,7 +2855,14 @@ pub(crate) fn synth(
.find_map(|((cls, m), _)| {
if *cls == c_class { Some(m.clone()) } else { None }
})
.unwrap_or_default();
.expect(
"class_methods registry coherence — a declared constraint's \
class is missing from env.class_methods. The pre-pass \
`MissingClass` diagnostic should have rejected this earlier; \
reaching here means workspace-registry / class-index drift. \
Surface to debug skill rather than silently render NoInstance \
with an empty method name.",
);
residuals.push(ResidualConstraint {
class: c_class,
type_: c_ty,
+52 -40
View File
@@ -552,6 +552,37 @@ fn apply_per_module_types_overlay(env: &mut crate::Env, ws: &Workspace, module_n
/// 22b.2 typecheck pass has already fired
/// `MissingConstraint`/`NoInstance` for any that should not exist
/// at this point.
/// Apply the current substitution to a meta and, if the result is
/// fully concrete, normalise it to canonical-form for registry lookup.
///
/// Returns `Some(normalised)` if the meta resolves to a concrete type;
/// `None` if it does not (rigid var or unbound meta — the caller
/// decides the policy: break with `has_rigid = true` at the FreeFn
/// target-collection site, or `Type::unit()`-default at the residual-
/// ordering site).
///
/// Iter 24.tidy: extracted from two byte-identical call sites at
/// `collect_mono_targets` and `collect_residuals_ordered` per
/// audit-24's [medium-2] drift item. The byte-identity invariant
/// (Phase 2 synthesis name must match Phase 3 rewrite cursor's
/// lookup name) is now enforced by construction.
fn apply_subst_and_normalize(
env: &crate::Env,
module_name: &str,
m: &Type,
subst: &crate::Subst,
) -> Option<Type> {
let resolved = subst.apply(m);
if crate::is_fully_concrete(&resolved) {
Some(
env.workspace_registry
.normalize_type_for_lookup(module_name, &resolved),
)
} else {
None
}
}
pub fn collect_mono_targets(
f: &AstFnDef,
module_name: &str,
@@ -685,32 +716,25 @@ pub fn collect_mono_targets(
let mut type_args: Vec<Type> = Vec::with_capacity(fc.metas.len());
let mut has_rigid = false;
for m in &fc.metas {
let resolved = subst.apply(m);
if crate::is_fully_concrete(&resolved) {
// Iter 24.3: normalise bare type-cons references to the
// canonical `<owner>.<bare>` form before they enter the
// MonoTarget. The synthesised body for a poly free fn
// lives in the fn's `owner_module` (e.g. `prelude` for
// `print`), but its `type_args` typically come from
// user-defining modules. If left bare, the synthesised
// body's `param_tys` carry bare references that later
// mono-walks (in the synthesised body's caller-module
// context — i.e. the fn's owner module) cannot resolve
// back to the registry's qualified instance key — and
// any nested class-method call (e.g. `show x` inside
// `print`'s body) silently produces no mono target,
// leaving the synthesised body referencing a bare class
// method that codegen later rejects.
let normalised = env
.workspace_registry
.normalize_type_for_lookup(module_name, &resolved);
type_args.push(normalised);
} else if contains_rigid_var(&resolved) {
has_rigid = true;
break;
} else {
// Unbound metavar — default to Unit (iter 23.4 behaviour).
type_args.push(Type::unit());
match apply_subst_and_normalize(&env, module_name, m, &subst) {
Some(normalised) => type_args.push(normalised),
None => {
// Helper returned None: either rigid var or unbound
// metavar. Site-1 policy diverges: rigid → break with
// `has_rigid = true` (the enclosing poly fn will be
// monomorphised in its own right and this site will
// be re-observed with concrete substitution); unbound
// metavar → default to Unit (iter 23.4 behaviour,
// matching `derive_substitution`'s unobservable-var
// policy in codegen).
let resolved = subst.apply(m);
if contains_rigid_var(&resolved) {
has_rigid = true;
break;
} else {
type_args.push(Type::unit());
}
}
}
}
if has_rigid {
@@ -1285,20 +1309,8 @@ pub(crate) fn collect_residuals_ordered(
.metas
.iter()
.map(|m| {
let resolved = subst.apply(m);
if crate::is_fully_concrete(&resolved) {
// Iter 24.3: canonical-form normalisation — see
// matching site in `collect_mono_targets` for
// rationale. Must agree byte-identically with
// that site or Phase 3 rewrite cursor produces
// a mono-symbol name that differs from the
// Phase 2 synthesis name.
env
.workspace_registry
.normalize_type_for_lookup(module_name, &resolved)
} else {
Type::unit()
}
apply_subst_and_normalize(&env, module_name, m, &subst)
.unwrap_or_else(Type::unit)
})
.collect();
Some(MonoTarget::FreeFn {
+71
View File
@@ -1692,6 +1692,77 @@ unresolved at the entry point — is a static error, not a runtime
one. This is the LLVM-friendly form and is consistent with
Decision 10's performance commitment.
### Cross-module references in synthesised bodies
The unified mono pass (per Decision 11's milestone-23.4 reorganisation)
synthesises mono symbols for polymorphic free fns and class-method
instances in the symbol's owner module — e.g. `print__Int` lives in
`prelude` (because `print` is defined in the prelude), but a
user-ADT call site `print (MkIntBox 7)` causes synthesis of
`prelude.print__IntBox` whose body references
`show_user_adt.show__IntBox` (the user instance lives in the
user-defining module per Decision 11 coherence). The synthesised body
crosses a module boundary the source template did not.
Three invariants make this work, all installed in milestone 24's iter
24.3 and worth keeping load-bearing:
1. **`MonoTarget::FreeFn::type_args` carries canonical types
post-collection.** At every site where `subst.apply(m)` produces a
concrete substitution that enters `MonoTarget::FreeFn::type_args`
(`crates/ailang-check/src/mono.rs::collect_mono_targets` and
`::collect_residuals_ordered`), the resolved `Type` must be passed
through `Registry::normalize_type_for_lookup(caller_module, &t)`
before being pushed. The downstream synthesised body's Phase 3
rewrite cursor (which runs in the OWNER module's context, not the
caller's) keys lookups in `Registry::entries` by the canonical
qualified form; a bare type-con reference at the type_args layer
silently drops the cross-module mono-symbol synthesis and leaves a
bare `Var "show"` post-mono that codegen later rejects with
`unknown variable`.
2. **Post-mono synthesised body cross-module references may bypass
the source template's `import_map`.** `prelude` does not import
user modules (the auto-injection runs one-way: user workspaces
import prelude, never the inverse). But a synthesised body for
`prelude.print__<UserType>` references `<user_module>.show__<UserType>`,
created by mono — not by the prelude source. Codegen's
cross-module name-resolution must accept this: at
`crates/ailang-codegen/src/lib.rs::resolve_top_level_fn` (Var-
resolution), `::lower_app`'s cross-module call arm, and
`::synth_with_extras`'s Var arm, the resolution first tries the
current module's `import_map`, then falls back to a direct
`module_user_fns` / `module_def_ail_types` lookup against the
prefix. Both ends were independently typechecked under their own
module contexts before mono ran; the cross-module reference is a
post-mono construct, not a source-language one.
3. **FreeFnCall synth pushes one residual per declared forall-
constraint.** At `crates/ailang-check/src/lib.rs`'s synth Var arm
for the `prefix.suffix` free-fn path, when the type is a
`Type::Forall { vars, constraints, body }`, instantiation produces
fresh metavars for the `vars` AND pushes one `ResidualConstraint`
per entry in `constraints` (with rigid vars substituted by the
freshly-generated metavars). The downstream discharge loop at
`check_fn`'s post-synth phase resolves each residual against the
workspace registry; if no instance satisfies the residual at the
unified concrete type, the `NoInstance` diagnostic fires at
typecheck (correctly), not at codegen (confusingly). Without the
residual push, milestone-23-shape negative cases (e.g. `print f`
where `f : Int -> Int`) silently typecheck and surface as
`unknown variable: show` from codegen instead of the right
typecheck-phase NoInstance Show.
The three invariants are lockstep partners: invariant (1) creates the
cross-module reference, invariant (2) makes codegen able to resolve
it, invariant (3) makes the typecheck-time discharge fire correctly
when no instance exists. A future refactor that loosens any one of
the three breaks the user-ADT trajectory; the test pins at
`crates/ail/tests/codegen_import_map_fallback_pin.rs` (invariant 2),
`crates/ail/tests/polyfn_dot_qualified_branch_pin.rs` (invariant 3
+ lockstep), and the existing `crates/ail/tests/show_user_adt`
fixture (full trajectory) collectively protect the contract.
### Defaults and superclasses
**Defaults.** A `ClassDef.methods[i].default` is either `null` (the
+157
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@@ -0,0 +1,157 @@
# iter 24.tidy — close 5 actionable drift items from audit-24
**Date:** 2026-05-13
**Started from:** 0e27533
**Status:** DONE
**Tasks completed:** 6 of 6
## Summary
Closes the 5 actionable drift items audit-24 surfaced (3× [high] +
2× [medium]): T1 adds a new DESIGN.md subsection
`### Cross-module references in synthesised bodies` under
`## Decision 11`'s `### Resolution and monomorphisation`, anchoring
the three iter-24.3 strengthenings as load-bearing lockstep
invariants (canonical-form type_args / import_map-fallback / FreeFnCall
constraint-residual push). T2 pins the codegen import_map-fallback
path with an integration test asserting the synthesised
`prelude.print__IntBox` body contains a `show_user_adt.show__IntBox`
Var AND the prelude source module does not import `show_user_adt`.
T3 pins the bare-name poly-fn dot-qualified-branch invariant by
asserting `show_no_instance.ail.json` produces exactly one
`no-instance` diagnostic and zero `unknown-variable` /
`internal` diagnostics. T4 tightens
`crates/ailang-check/src/lib.rs:2852` from `unwrap_or_default()` to
`.expect(...)` with a registry-coherence panic message; the strict
tightening surfaced no existing violations (558 tests pass post-edit).
T5 extracts the duplicated `subst.apply + is_fully_concrete +
normalize_type_for_lookup` body into a single `apply_subst_and_normalize`
helper returning `Option<Type>`, replacing the two byte-identical
sites at `mono.rs::collect_mono_targets` (685-714) and
`::collect_residuals_ordered` (1284-1303); the byte-identity
invariant is now enforced by construction, `mono_hash_stability`
green on both primitive Show + Eq/Ord hashes. T6 verifies: 558
tests pass (was 556 + 2 new pins, exactly the expected count);
`bench/cross_lang.py` exit 0 (25/25 stable); `bench/compile_check.py`
exit 0 with 4 `check_ms.*` noise-class regressions in the documented
audit-24 lineage; `bench/check.py` exit 0 with 3 `latency.implicit_at_rc.*`
+ 4 `latency.explicit_at_rc.*` noise-class observations in the same
lineage (10th consecutive observation; baseline pristine).
## Per-task notes
- iter 24.tidy.1 (T1): DESIGN.md +68 lines, new `### Cross-module
references in synthesised bodies` subsection inserted between
`### Resolution and monomorphisation` (ends line 1693) and the
re-anchored `### Defaults and superclasses`. Subsection enumerates
three lockstep invariants with cross-references to source files
(`mono.rs::collect_mono_targets` / `::collect_residuals_ordered`,
`codegen/lib.rs::resolve_top_level_fn` / `::lower_app` /
`::synth_with_extras`, `check/lib.rs` synth FreeFnCall arm) and
to the protective test pins. Closing paragraph names the lockstep
partnership and the regression cost of loosening any one.
- iter 24.tidy.2 (T2): New `crates/ail/tests/codegen_import_map_fallback_pin.rs`.
Loads `examples/show_user_adt.ail.json`, runs `check_workspace` +
`monomorphise_workspace`, finds the synthesised `Def::Fn` whose
name starts with `print__` in the `prelude` post-mono module,
recursively walks its body looking for a `Term::Var { name }`
whose name starts with `show_user_adt.` and contains `show__`,
and confirms the prelude source module's `Vec<Import>` does NOT
include `show_user_adt`. Plan draft adapted at three points: (a)
`Term::App` field name is `callee` not `fn` (the latter is the
serde rename; Rust field is `callee`); (b) `imports.iter()` gives
`&Import` not `&String` so the check is on `imp.module`; (c)
recursive walker extended with `Seq` / `Clone` / `ReuseAs` /
`LetRec` / `If` / `Match` / `Ctor` arms for exhaustiveness — all
data-shape adaptations the plan explicitly authorised. Test passes
first-shot (1 passed).
- iter 24.tidy.3 (T3): New `crates/ail/tests/polyfn_dot_qualified_branch_pin.rs`.
Loads `examples/show_no_instance.ail.json`, asserts exactly one
`no-instance` diagnostic AND zero `unknown-variable` / `internal`
diagnostics. The plan's draft `d.code` field accesses match the
actual `Diagnostic` struct (verified against
`crates/ailang-check/src/diagnostic.rs:131`). Test passes first-shot.
- iter 24.tidy.4 (T4): One-line tightening at
`crates/ailang-check/src/lib.rs:2858` —
`.unwrap_or_default()` → `.expect("class_methods registry coherence ...")`
with the verbatim plan message. The `.expect(...)` covers the
registry-coherence invariant: a declared constraint's class is
expected to be in `env.class_methods` because the pre-pass
`MissingClass` diagnostic should have rejected it earlier; reaching
this point with `None` means workspace-registry / class-index drift.
No existing test violates the new invariant — 558 tests pass.
- iter 24.tidy.5 (T5): New `apply_subst_and_normalize` helper at
`crates/ailang-check/src/mono.rs:555-583` (immediately preceding
`collect_mono_targets`). Signature
`fn apply_subst_and_normalize(env: &crate::Env, module_name: &str, m: &Type, subst: &crate::Subst) -> Option<Type>`.
Returns `Some(normalised)` if `subst.apply(m)` is fully concrete
(via `crate::is_fully_concrete`); else `None`. Two call sites
retrofit: site 1 at `collect_mono_targets` (now ~ lines 707-727)
keeps its rigid-var / Unit-default branching at the call site
(helper-None → check `contains_rigid_var(&subst.apply(m))`; if
rigid set `has_rigid = true` and break; else push `Type::unit()`);
site 2 at `collect_residuals_ordered` (now ~ lines 1284-1290) uses
`apply_subst_and_normalize(&env, ...).unwrap_or_else(Type::unit)`.
Site 1 needed `&env` (local owned `Env`) where the plan draft had
bare `env` — one-character edit. `mono_hash_stability` both tests
pass (primitive Show + Eq/Ord mono-symbol hashes bit-identical),
full workspace 558 green. Byte-identity invariant now enforced by
construction at the helper boundary; each call site explicitly
documents its post-helper-None policy.
- iter 24.tidy.6 (T6): Integration verification. Full workspace
`cargo test --workspace --no-fail-fast` = 558 passed, 0 failed
(matches plan's prediction: 556 baseline + 2 new pins). No
FAILED entries among milestone-24 specific test groups
(show_/print_/prelude_free_fns/mono_hash_stability/typeclass_22b/mq3).
Bench: `cross_lang.py` exit 0, 25/25 stable; `compile_check.py`
exit 0 with 4 `check_ms.*` ms-level noise-class regressions
(`hello`, `borrow_own_demo`, `bench_tree_walk`, `bench_hof_pipeline`);
`check.py` exit 0 with 3 noise-class regressions
(`latency.implicit_at_rc.{p99_9_us, max_us}` first-sightings in
this iter) + 4 noise-class improvements
(`latency.explicit_at_rc.{p99_us, p99_over_median}` improvements
continuing the documented audit-cma → audit-24 lineage). 10th
consecutive observation of metric-identity-migrating noise;
baseline pristine, conservative-call convention holds per the
documented lineage.
## Concerns
- T5 pre-extraction reading vs plan: the plan said site 1's unbound-
meta path "likely a `continue` without push" — actual pre-extraction
code did `type_args.push(Type::unit())` for unbound metas (iter 23.4
behaviour, comment in place). I preserved the actual behaviour, not
the plan's guess. Lockstep with site 2 (which has the same Unit-default
policy) is improved post-extraction. Observation, not correctness.
- T2 plan draft had three data-shape mismatches against actual Rust
schema (`Term::App.callee` vs plan's `fn`, `Vec<Import>` vs
`Vec<String>`, exhaustive Term variants). The plan explicitly
flagged these as "implementer adapts to the actual field name"
cases; not plan defects but recon imprecisions.
## Known debt
- audit-24 [medium-3] negative-test coverage breadth → deferred to
P3 downstream-corpus-migration milestone (carried over from
audit-24, not closed here).
- audit-24 [low-1] bench/architect_sweeps.sh noise → carry-on,
pre-milestone-24 lines not new drift.
## Files touched
- `docs/DESIGN.md` — new subsection (T1), +68 lines.
- `crates/ail/tests/codegen_import_map_fallback_pin.rs` — new pin (T2).
- `crates/ail/tests/polyfn_dot_qualified_branch_pin.rs` — new pin (T3).
- `crates/ailang-check/src/lib.rs` — one-line tightening at :2858 (T4).
- `crates/ailang-check/src/mono.rs` — new helper + two call-site
replacements (T5).
## Stats
`bench/orchestrator-stats/2026-05-13-iter-24.tidy.json`