iter 22b.4a: journal entry

2026-05-09 22:30:17 +02:00
parent 0709e319ab
commit 692899867b
1 changed files with 105 additions and 0 deletions
@@ -11603,3 +11603,108 @@ Prelude declares `Show`, `Eq`, `Ord` over `Int`, `Bool`, `Str`
 through `Show.show`, Form-B class/instance prose lands, round-trip
 filter retires. End-to-end gate: any prior `print 42`-style fixture
 must keep working through `Show.show#Int`.
+
+## 2026-05-09 — Iteration 22b.4a: Form-A parser+printer arms for ClassDef/InstanceDef (and forall-constraints gap fix)
+
+Closes the round-trip gap that 22b.1 deliberately deferred: every
+`examples/*.ail.json` fixture now round-trips through
+`parse(print(M))` with canonical-equal JSON, including the
+`test_22b1_*`, `test_22b2_*`, `test_22b3_*` typeclass fixtures that
+the skip-list excluded. 106 fixtures green (up from 70). Bench gates
+all 0/0/0.
+
+**Per-task subjects (mirror commit messages):**
+
+- 22b.4a.1: form-a parser arm for ClassDef
+- 22b.4a.2: form-a parser arm for InstanceDef
+- 22b.4a.3: form-a printer arm for ClassDef
+- 22b.4a.4: form-a printer arm for InstanceDef
+- 22b.4a.4.5: form-a printer+parser arms for Type::Forall constraints (gap fix)
+- 22b.4a.5: retire round-trip skip-list for class/instance fixtures
+- 22b.4a.6: spec + DESIGN amendments — 22b.4 split, terminology fix, '__' separator, forall-constraints gap
+
+**S-expression form locked:**
+
+ClassDef:
+
+    (class <Name>
+      (param <ident>)
+      [(superclass (class <Name>) (type <ident>))]
+      [(doc "...")]
+      (method <name> (type <fn-type>) [(default <body>)])*)
+
+InstanceDef:
+
+    (instance
+      (class <Name>)
+      (type <type-expr>)
+      [(doc "...")]
+      (method <name> (body <term>))*)
+
+Type::Forall constraints (extension to existing forall-type form):
+
+    (forall (vars …)
+            [(constraints (constraint <Class> <type>)+)]
+            <body>)
+
+**Iteration split rationale:** the brainstorm-original 22b.4 bundled
+surface arms with the Prelude module + `int_to_str` C-runtime
+primitive + end-to-end `show 42` fixture. Surface arms touch one
+crate with no runtime risk; the Prelude work touches `runtime/`,
+`ailang-codegen`, `ailang-check::builtins`, plus codegen wiring for
+the new primitive. Different review surface, different risk profile,
+different bench-gate exposure. The split (22b.4a / 22b.4b) is
+recorded in the spec amendments section and is the substantive
+follow-up for 22b.4b.
+
+**Terminology fix:** the original spec called the surface arms
+"Form-B parser/printer arms". `crates/ailang-surface` is in fact
+**Form-A** (parseable s-expression); `crates/ailang-prose` is Form-B
+(one-way prose, no parser by design). The 22b.1 round-trip-skip-list
+comment carried the same conflation. Both corrected in the spec
+amendment.
+
+**Mid-iter gap fix:** Task 5's pre-flight surfaced that the existing
+Form-A arms dropped `Type::Forall.constraints` (the field added in
+22b.2). Four `test_22b2_*` fixtures regressed when the filter was
+lifted. Fixed inline via 22b.4a.4.5 by extending `parse_forall_type`
+and the `Type::Forall` arm of `write_type` to round-trip the
+constraints clause. The skip-list had silently masked this gap
+alongside the ClassDef/InstanceDef gap; retiring it required closing
+both in the same iter.
+
+**Quality-review carry-overs:**
+
+- Strict duplicate-clause detection in the new parser arms
+  (`(param ...)`, `(superclass ...)`, `(doc ...)`, `(method (type
+  ...))`, `(method (body ...))`) — sibling parsers (`parse_fn`,
+  `parse_data`, `parse_const`) silently overwrite earlier clauses
+  with later ones. The new strict pattern is correct; the silent
+  pattern is the wart. Promoting siblings to the strict pattern is
+  out of scope for 22b.4a (it would expand to all existing fixtures
+  and require their own RED tests). Filed as known debt.
+- `pos: 0` fallback in missing-required-clause errors — pre-existing
+  pattern across all def parsers; mirroring it in the new code
+  preserves consistency. Targeted fix would be cross-crate and
+  belongs in a separate iter.
+
+**Known debt (deferred to 22b.4b or later):**
+
+- Form-B (prose) printer arms for ClassDef / InstanceDef. One-way,
+  not gating; queued for the audit cycle or 22b.4b cleanup.
+- DESIGN.md line 1749 ("the exact textual form is fixed in 22b
+  alongside the existing mangling scheme") still does not name
+  `__` directly. The load-bearing rationale was added at line 1607
+  (the `show__Int` example paragraph); line 1749 is a forward
+  reference whose update is audit-cycle work.
+- Strict duplicate-clause detection in `parse_fn` / `parse_data`
+  / `parse_const` — file as known asymmetry, do not retrofit in
+  22b.4a.
+
+**Bench gates:** all three (`bench/check.py`, `bench/compile_check.py`,
+`bench/cross_lang.py`) exited 0/0/0 (matches 22b.3 close).
+
+**Next iter (queued):** 22b.4b — Prelude module with `class Show
+a where show : (a borrow) -> Str`, `instance Show Int`, the
+`int_to_str` C-runtime primitive, codegen wiring, and an end-to-end
+`show 42` fixture printing `42` through the mono pass.