Decision 8 ships. Term::App and Term::Do gain tail: bool with
serde-default false and skip-when-false serialisation. New
typecheck pass verify_tail_positions enforces tail-position rules
(Scheme-style propagation through match arms, seq.rhs, let body,
lam body). Codegen emits musttail call for marked App calls.
Hash invariance verified: only the two migrated print_list defs
(list_map_poly.print_list, sort.print_list) changed hashes; all
other defs across all 18 fixtures kept bit-identical hashes —
confirms the skip-when-false serialisation rule works.
Tests 76 -> 79: tail_call_in_non_tail_position_is_rejected,
tail_call_in_tail_position_is_accepted, plus an IR-grep e2e test
asserting that print_list's recursive call site emits musttail
in the lowered IR. Existing 25 e2e tests unchanged in behaviour
(map -> [2,3,4], sort -> sorted list).
IR evidence at the recursive site:
%v7 = musttail call i8 @ail_list_map_poly_print_list(ptr %v6)
ret i8 %v7
Two deviations called out in the implementer report and JOURNAL:
1. tail-do uses tail call, not musttail. Cross-type return
(runtime helpers return i32, AILang Unit is i8) would have
LLVM reject musttail. Path is implemented but not exercised
by any current fixture; proper fix is runtime-helper signature
change, punted.
2. block_terminated flag in codegen so tail-call emit
(musttail call + ret) doesn't get a duplicate trailing ret
from surrounding code (match-arm phi, fn-body, lambda thunk).
Internal plumbing; required for IR well-formedness.
Form (A) productions now at ~30, exactly the constraint-1
budget. Future surface additions need to retire something or
explicit-budget-rebalance in DESIGN.md.
GC notes from implementer survey land in JOURNAL:
- Allocations cluster in lower_ctor; every term-ctor does
malloc(8+8n).
- Tail recursion does not reduce alloc pressure, only stack.
For map-style ctor-blocked recursions, allocation IS the
bottleneck.
- Per-fn arena is sound only when fn return type contains no
boxed ADT. Most current fixtures violate this.
Plan 14f: Boehm conservative GC (GC_malloc, -lgc) as a first
cut. Single-iter integration, no AST/schema change. Stress
test: build a 100k Cons list, observe RSS doesn't blow up.
After 14f the language is feature-complete enough for stdlib
work (15a).
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
Term::If was semantically a subset of Term::Match on Bool. Per
CLAUDE.md the language must contain no redundancies; two AST nodes
for the same operation produces an authoring decision with no
semantic content and a duplicate codegen path. Removed.
Migration shape (applied to sum, sort, max3 fixtures):
(if c a b) -> (match c (case (lit-bool true) a) (case _ b))
No schema version bump (per user direction): no third-party consumes
ailang/v0, so version ceremony is pure overhead. Edited AST and
fixtures in place; pinned hashes in hash.rs updated.
Implementer deviation, called out and justified: a tightly-scoped
lower_bool_match helper (~95 LOC) was needed in codegen because
the existing match path rejects i1 scrutinees and Pattern::Lit.
Helper accepts only the canonical two-arm migration shape, errors
on anything else, emits the same br/phi IR Term::If used to. No
generalisation of the ADT-match codegen.
Diff: 13 files, +286/-221 (net +65 LOC). AST got smaller
(one variant gone), form-(A) got smaller (one production gone),
typecheck got smaller (one branch gone). Codegen got slightly
larger by the bool-match helper.
Hash deltas: sum.sum, sort.insert, max3.max, max3.max3 changed.
All other defs (e.g. sum.main, sort.IntList, sort.sort,
sort.print_list, max3.main) kept bit-identical hashes — confirms
canonical-JSON byte format intact.
Verification: 76/76 tests green; sum->55, max3->17, sort->[1,1,2,
3,3,4,5,5,5,6,9] (identical to pre-migration). cargo doc 0 warnings.
Tail-call survey by implementer (informs 14e): print_list
recursions are already in tail position (rhs of seq inside match
arm); map/sort/insert recursions are NOT (constructor-blocked
inside Cons applications). 14e annotation will benefit terminal
recursions; ctor-blocked ones need accumulator-form rewrites in
source, not a compiler-side transform.
Decision 7 added to DESIGN.md. JOURNAL entry has the language-
completion sequence (14d done, 14e tail-calls, 14f GC, 15a stdlib).
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
Strictly additive new crate per Decision 6 architectural pin.
JSON-AST stays the source of truth; ailang-surface is one
producer/consumer of ailang_core::ast::Module values. ailang-check
and ailang-codegen unchanged.
Crate contents:
- src/lex.rs (~264 LOC): 3-rule lexical core. Whitespace and parens
delimit tokens; semicolon to EOL is comment; first-character
classifier (digit -> int, " -> string, else -> ident).
- src/parse.rs (~1041 LOC): hand-written recursive descent. One Rust
fn per EBNF production. No parser-combinator dep.
- src/print.rs (~371 LOC): deterministic pretty-printer. Round-trip
contract with parse() is the surface's correctness gate.
- tests/round_trip.rs (~128 LOC): integration test runs every
examples/*.ail.json fixture through print -> parse -> canonical
JSON, asserts canonical-byte equality with the original.
Two AST-driven form widenings beyond the 14b sketch (both folded
into DESIGN.md Decision 6):
- lam-term carries (typed name type) params, ret type, and
optional effects (Term::Lam has parallel param_tys/ret_ty/
effects fields).
- import-clause admits (import name (as alias)?) (Import.alias
is Option<String>).
Production count ~28, under 30-rule budget. Constraint 1
(formalisable for foreign LLM) intact.
Verification:
- cargo build --workspace green.
- cargo test --workspace: 76 tests green (was 64; +9 surface unit,
+2 round-trip integration). All 17 fixtures round-trip
byte-identical at canonical level. 3 hand-written .ailx
exhibits parse to canonical JSON identical to their .ail.json
siblings.
- cargo doc --no-deps zero warnings (DESIGN.md item 6 invariant).
Manual smoke test (ail parse → ail run): hello, box,
list_map_poly all produce expected output through the form-(A)
authoring lane end-to-end.
CLI: ail parse <file.ailx> [-o <file.ail.json>]. .ail.json
remains a first-class input to every existing subcommand.
Plan 14d: stdlib (std_list.ailx with length/filter/fold/concat/
reverse/head/tail), authored in form (A) from day one.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
Brummel