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.
First iteration of the mut-local milestone (foundation step on the
Stateful-islands roadmap path). Lands the schema + surface tier:
Term::Mut, Term::Assign, and the nested MutVar struct become
first-class AST nodes that round-trip cleanly through Form A.
Typecheck and codegen recognition are deferred to mut.2 and mut.3
per the spec's out-of-iteration boundary; reaching either dispatch
entry point with these variants produces CheckError::Internal /
CodegenError::Internal with a 'deferred to iter mut.{2,3}' message.
Concretely:
- crates/ailang-core/src/ast.rs: two new Term variants behind
#[serde(tag = 't')]; pub struct MutVar { name, ty, init } adjacent
to Arm. Two canonical-bytes pin tests for the explicit-empty-vars
serialisation and the assign round-trip.
- ~25 substantive Term-walker arms across ailang-core/desugar,
ailang-core/workspace, ailang-check (lib + lift + linearity + mono
+ pre_desugar_validation + reuse_shape + uniqueness),
ailang-codegen (escape + lambda + lib), ailang-prose, and
crates/ail/src/main.rs. Universal policy: substantive recurse-into-
children at every site; only the two dispatch entry points
(synth in ailang-check, lower_term in ailang-codegen) stub with
Internal-error. One test-side walker arm in
crates/ail/tests/codegen_import_map_fallback_pin.rs not
enumerated by the plan was added as well (defensive recursion).
- ailang-surface: parse_mut + parse_assign helpers; Term::Mut
body desugared from a flat statement sequence into a right-folded
Term::Seq chain inside the JSON-AST. Print arms in print.rs match
the parser convention. EBNF prologue + crates/ailang-core/specs/
form_a.md productions updated. Four new parser pin tests cover
the empty-mut, single-var, body-required, and vars-only-no-body
cases.
- Drift + coverage tests extended: design_schema_drift.rs adds two
exemplars + match arms; schema_coverage.rs adds two VariantTag
entries + EXPECTED_VARIANTS + visit_term arms; spec_drift.rs adds
two exemplars + match arms. DESIGN.md §'Term (expression)' gets
jsonc-blocked schemas for the two new variants.
- examples/mut.ail: six-fn round-trip fixture exercising empty mut,
single-var, two-var, nested-shadow, and the four supported scalar
return types (Int, Float, Bool, Unit). The round_trip auto-glob
and schema_coverage corpus walker both pick it up.
Plan deviation: the plan named lib.rs:2572 as the typecheck
dispatch stub site, but that line is actually verify_tail_positions
(substantive walker). The real dispatch is synth (3403-area, stub
at 3489); the orchestrator routed correctly.
Tests: 564 → 579 green; cargo build green; round-trip green for
the new fixture; all drift + coverage tests green.
Journal: docs/journals/2026-05-15-iter-mut.1.md.
Refs: docs/specs/2026-05-15-mut-local.md, docs/plans/2026-05-15-iter-mut.1.md.
Three new reader-only tests pin the .ail.json / .ailx bijection
plus AST-variant coverage. All three passed first observation
across the current corpus — no roundtrip, schema-coverage, or
CLI-drift gaps surfaced.
- every_ailx_fixture_matches_its_json_counterpart (replaces the
3-pair handwritten exhibits): 57 paired .ailx fixtures pass.
- every_ast_variant_is_observed_in_the_fixture_corpus (new): 34/34
AST variants exercised across 136 fixtures; exhaustive matches
without _ wildcard so AST drift fails the build.
- cli_render_then_parse_preserves_canonical_bytes_on_every_fixture
(new): 136 fixtures round-trip through ail render → tempfile →
ail parse with BLAKE3 identity on canonical bytes.
No production code, no DESIGN.md changes (those follow in later
iterations). Tests are pure readers of the repo per spec
acceptance #7 — tempfile crate added as workspace dep for the CLI
roundtrip's intermediate file outside the repo.
Brummel