haskell: Phase 14 — record patterns Foo { f = b } in case + fun-clauses

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

plans/haskell-completeness.md

@@ -259,7 +259,7 @@ No OCaml changes are needed. The view type is fully representable as an SX dict.
   tagged list. Field → index mapping stored in `hk-constructors` at registration.
   _Field map lives in `hk-record-fields` (desugar.sx) for load-order reasons,
   not `hk-constructors`._
-- [ ] Exhaustive record patterns: `Foo { bar = b }` in case binds `b`,
+- [x] Exhaustive record patterns: `Foo { bar = b }` in case binds `b`,
   wildcards remaining fields.
 - [ ] Tests in `lib/haskell/tests/records.sx` (≥ 12 tests: creation, accessor,
   update one field, update two fields, record pattern, `deriving Show` on
@@ -315,6 +315,18 @@ No OCaml changes are needed. The view type is fully representable as an SX dict.
 
 _Newest first._
 
+**2026-05-07** — Phase 14 record patterns `Foo { bar = b }`:
+- Parser: `hk-parse-pat-lhs` now peeks for `{` after a conid; if found, calls
+  `hk-parse-rec-pat` which collects `(fname pat)` pairs and emits `:p-rec`.
+- Desugar: `:p-rec` → `:p-con` with positional pattern args; missing fields
+  become `:p-wild`s. The `:alt` desugar case now also recurses into the
+  pattern (was only desugaring the body); the `:fun-clause` case maps
+  desugar over its param patterns. Both needed for the field-name → index
+  lookup to fire on `:p-rec` nodes inside case alts and function clauses.
+- Verified end-to-end: case-alt record patterns, multi-field bindings, and
+  function-LHS record patterns all work. No regressions in match (31/31),
+  eval (66/66), desugar (15/15), deriving (15/15), quicksort (5/5).
+
 **2026-05-07** — Phase 14 record-update syntax `r { field = v }`:
 - Parser: `varid {` after a primary expression now triggers
   `hk-parse-rec-update` returning `(:rec-update record-expr [(fname expr) …])`.