First implementation contact surfaced a plan defect: the
borrow-over-value reject cannot land green as a standalone pre-cutover
task. The prelude's polymorphic comparison builtins are
`(params (borrow a) …)` (eq/compare/lt/…); the mono pass
(apply_subst_to_type, subst.rs:165) specialises `a := Int/Bool/Float`
into `compare__Int(borrow Int, …)` — the language's OWN generated code
in the forbidden `(borrow value-type)` shape. The standalone check
broke compare_{int,bool}_mono_symbol_emits_branch_ladder.
Spec 0062's "value types always own" rule is universal, so generated
code must honour it too: the principled fix is a mono-pass coercion
`(borrow value-type) -> (own value-type)` (a no-op — value types carry
no RC, so own vs borrow emits no inc/dec and the branch-ladder IR is
unchanged). The check and the coercion are a matched pair and now live
together in Task 4 (Steps B1-B2), which touches the mono path anyway.
Pre-cutover green tasks are now Task 1 (borrow-return reject) + Task 3
(throwaway migration tool). Task 1's check_def destructure binds only
ret_mode (param_modes stays under `..`); Task 4 Step B2 widens it.
Spec gap to record at the next 0062 brainstorm touch: the
borrow-over-value rule needs its mono-coercion clause spelled out — the
spec tested only the authored case.
refs #55
Executable projection of spec 0062 (#55) into four tasks: (1) the
borrow-return reject, (2) the borrow-over-value reject, (3) a throwaway
`ail migrate-modes` pass (parse -> Implicit->Own, keep explicit
own/borrow -> print explicit), (4) the atomic cutover (run the
migration over the corpus + hand-fix the read-only-heap params the
now-universal linearity check flags, delete the variant + all
compile sites compiler-driven, parser bare-slot reject, reset the hash
pins, flip the leak pin, update both contracts, drop the throwaway).
Placeholder-free; all seven surface fixtures parse-gated against HEAD.
Spec 0062 marked approved (user, 2026-06-01) and its soundness
re-validated against post-#56 HEAD: the three own-return-provenance /
regime-A fixtures still exit 1 under [consume-while-borrowed]; #56's
application-is-a-borrow change does not weaken them (none is an
application of a borrowed binder).
plan-recon folded four spec-enumeration corrections into the plan:
- kernel migration target is raw_buf/source.ail, not the retired
kernel_stub/source.ail the spec cited;
- FIVE hash pins shift, not the two the spec named (embed_export_hash,
eq_ord_e2e, mono_hash_stability are the missed twins);
- design/contracts/0002-data-model.md also documents the "implicit"
JSON form and is drift-anchored -> updates alongside 0008;
- real counts are 261 fn-type fixtures (spec ~208) and 17 fn_implicit
references (spec 16); the compiler is the authoritative enumerator.
refs #55
Brummel