haskell: top-level decls (fn-clause, type-sig, data, type, newtype, fixity) + type parser (+24 tests, 162/162)

plans/haskell-on-sx.md

@@ -60,7 +60,7 @@ Key mappings:
   - [x] Expressions: atoms, parens, tuples, lists, ranges, application, infix with full Haskell-98 precedence table, unary `-`, backtick operators, lambdas, `if`, `let`
   - [x] `case … of` and `do`-notation expressions (plus minimal patterns needed for arms/binds: var, wildcard, literal, 0-arity and applied constructor, tuple, list)
   - [x] Patterns — full: `as` patterns, nested, negative literal, `~` lazy, infix constructor (`:` / consym), extend lambdas/let with non-var patterns
-  - [ ] Top-level decls: function clauses, type signatures, `data`, `type`, `newtype`, fixity decls
+  - [x] Top-level decls: function clauses (simple — no guards/where yet), pattern bindings, multi-name type signatures, `data` with type vars and recursive constructors, `type` synonyms, `newtype`, fixity (`infix`/`infixl`/`infixr` with optional precedence, comma-separated ops, backtick names). Types: vars / constructors / application / `->` (right-assoc) / tuples / lists. `hk-parse-top` entry.
   - [ ] `where` clauses + guards
   - [ ] Module header + imports (stub)
   - [ ] List comprehensions + operator sections
@@ -114,6 +114,31 @@ Key mappings:
 
 _Newest first._
 
+- **2026-04-24** — Phase 1: top-level decls. Refactored `hk-parse-expr` into a
+  `hk-parser tokens mode` with `:expr` / `:module` dispatch so the big lexical
+  state is shared (peek/advance/pat/expr helpers all reachable); added public
+  wrappers `hk-parse-expr`, `hk-parse-module`, and source-level entry
+  `hk-parse-top`. New type parser (`hk-parse-type` / `hk-parse-btype` /
+  `hk-parse-atype`): type variables (`:t-var`), type constructors (`:t-con`),
+  type application (`:t-app`, left-assoc), right-associative function arrow
+  (`:t-fun`), unit/tuples (`:t-tuple`), and lists (`:t-list`). New decl parser
+  (`hk-parse-decl` / `hk-parse-program`) producing a `(:program DECLS)` shell:
+  - `:type-sig NAMES TYPE` — comma-separated multi-name support
+  - `:fun-clause NAME APATS BODY` — patterns for args, body via existing expr
+  - `:pat-bind PAT BODY` — top-level pattern bindings like `(a, b) = pair`
+  - `:data NAME TVARS CONS` with `:con-def CNAME FIELDS` for nullary and
+    multi-arg constructors, including recursive references
+  - `:type-syn NAME TVARS TYPE`, `:newtype NAME TVARS CNAME FIELD`
+  - `:fixity ASSOC PREC OPS` — assoc one of `"l"`/`"r"`/`"n"`, default prec 9,
+    comma-separated operator names, including backtick-quoted varids.
+  Sig vs fun-clause disambiguated by a paren-balanced top-level scan for
+  `::` before the next `;`/`}` (`hk-has-top-dcolon?`). 24 new tests in
+  `lib/haskell/tests/parser-decls.sx` cover all decl forms, signatures with
+  application / tuples / lists / right-assoc arrows, nullary and recursive
+  data types, multi-clause functions, and a mixed program with data + type-
+  synonym + signature + two function clauses. Not yet: guards, where
+  clauses, module header, imports, deriving, contexts, GADTs. 162/162 green.
+
 - **2026-04-24** — Phase 1: full patterns. Added `as` patterns
   (`name@apat` → `(:p-as NAME PAT)`), lazy patterns (`~apat` →
   `(:p-lazy PAT)`), negative literal patterns (`-N` / `-F` resolving