Second of three iterations of the standalone loop/recur milestone
(plan 5ac57fe). Replaces the iter-1 synth CheckError::Internal stub
for Term::Loop/Term::Recur with real binder typing + positional
recur arity/type checking via a new loop_stack: &mut Vec<Vec<Type>>
frame threaded as mut.2's mut_scope_stack, a new private
verify_loop_body tail-position pass (sibling of the byte-frozen
verify_tail_positions — 0 deletions there), and the four Recur*
diagnostics firing point-exactly on four negative fixtures. The
iter-1 loop_sum_to.ail fixture now also typechecks clean; an
infinite loop typechecks (no termination claim). NO codegen (the
iter-1 lower_term stub stays — iter 3); NO Diverge/guardedness
(spec boundary).
Three Boss design calls implemented verbatim and journalled:
RecurTypeMismatch is an Assign-style structural pre-check (not a
unify-propagate); loop_stack is positional Vec<Type> (binder names
via ordinary locals); diagnostic-code precedence is by pass
ordering (no explicit logic).
Two DONE_WITH_CONCERNS, both journalled: a plan-ordering defect
(Task 2's compile gate forced the check_fn threading the plan
deferred to Task 4 — resolved byte-identically, only resequenced)
and the recurring mut.2-class recon-undercount of cross-module
synth callers (resolved via the plan's compile-sweep oracle).
Boss systemic fix folded in: planner SKILL.md Step-5 gains item 7
(compile-gate vs. deferred-caller ordering) so the plan-ordering
defect class is scrubbed at plan time. cargo test --workspace
608 -> 616 / 0 red (Boss-reran independently).
One forward iteration; main never rewound. 1ff7e81 (the pre-9973546
commit) is the per-region byte oracle — every reverted source/test
file is byte-identical to it; crates/ailang-check/src/lib.rs fully so.
Root cause being corrected: the Iteration-discipline milestone was an
over-escalation of fieldtest finding F1 (a [friction] item whose own
minimal recommendation was a DESIGN.md note). Its totality dichotomy
made the maximally-LLM-natural build(d:Int)=Node(1,build(d-1),
build(d-1)) inexpressible (it.3 BLOCKED); the only in-thesis escape
(A1/it.2b) conceded the language's first documented-unenforced
totality precondition — a purity-pillar dilution the user rejected in
favour of a full revert + rebuild.
Removed: Term::Loop/Term::Recur/LoopBinder; the verify_structural_
recursion guardedness pass + term_contains_loop + Diverge-injection +
the transitively-it.2 module_fns plumbing; the five Recur*/
NonStructuralRecursion CheckError variants (+ code() + the 3 dedicated
ctx() arms); the it.1 codegen loop-header/phi/back-edge + parallel
block_terminated setter; all Loop/Recur walker arms; 16 it.1/it.2
fixtures; 2 pin files; bench/it3-oracle/. Restored: 2 RC fixtures to
1ff7e81 content.
Surgically kept (not in 1ff7e81, landed with the milestone but
independently sound): feature-acceptance clause 3 in DESIGN.md and
skills/brainstorm/SKILL.md, with its worked example de-claimed from
"shipped" to hypothetical-illustration form; the F3 P2 todo.
bench/orchestrator-stats/2026-05-15-iter-it.{1,2,3}.json kept as
historical record (like journals/plans).
Sole net addition: an honest F1/F4 documented-idiom note in DESIGN.md
(the tail-recursive accumulator fallback; examples/mut_counter.ail),
guarded by a doc-presence test — "a documentation note is not a
reshape", asserts nothing at the typecheck level.
Roadmap: the Iteration-discipline block + blocking-fork section
removed; the genuine total-Int-recursion ambition preserved as a
deferred P2 milestone sequenced behind a future Nat/refinement-types
milestone (not abandoned — correctly sequenced after the type
machinery it needs). 2026-05-15-iteration-discipline.md carries a
superseded header; it.1/it.2/it.3 journals + plans stay as history.
Correctness gate PRISTINE: 164 surviving 1ff7e81-era fixtures
ail check/ail run byte-identical to pre-milestone behaviour (verified
against a 1ff7e81 worktree reference compiler, zero drift);
cargo test --workspace 600/0; zero residual it.1/it.2 production
surface.
Spec docs/specs/2026-05-16-iteration-discipline-revert.md (b3853bf),
plan docs/plans/2026-05-16-iter-revert.md (abf0013).
Iteration-discipline milestone, 1 of 3. Adds named loop + recur as
strictly-additive first-class AST nodes: parse/print/prose/serde/
round-trip/schema lockstep, typecheck (binder typing + recur
arity/type unification via loop_stack threaded as mut.2's
mut_scope_stack; recur-tail-position via verify_loop_body), codegen
(loop-header + one phi per binder; recur back-edge br with a NEW
parallel block_terminated setter; lambda-boundary loop_frames
save/restore). Four Recur* CheckError variants. Strictly additive:
zero deletions touch tail-app/tail-do or the seven existing
block_terminated sites — this is what makes the destructive it.3
safe. recur synth = fresh metavar (resolves the plan's flagged
Type::unit() risk). loop_counter->55, loop_in_lambda->49, four
negatives fire, tail-app byte-identical, cargo test --workspace
green. Spec fda9b78, plan 7381a42.
Brummel