haskell: classic program fib.hs + source-order top-level binding (+2 tests, 388/388)

plans/haskell-on-sx.md

@@ -82,7 +82,7 @@ Key mappings:
 - [x] `seq`, `deepseq` from Prelude
 - [x] Do-notation for a stub `IO` monad (just threading, no real side effects yet)
 - [ ] Classic programs in `lib/haskell/tests/programs/`:
-  - [ ] `fib.hs` — infinite Fibonacci stream
+  - [x] `fib.hs` — infinite Fibonacci stream
   - [ ] `sieve.hs` — lazy sieve of Eratosthenes
   - [ ] `quicksort.hs` — naive QS
   - [ ] `nqueens.hs`
@@ -114,6 +114,23 @@ Key mappings:
 
 _Newest first._
 
+- **2026-04-25** — First classic program: `fib.hs`. Canonical Haskell
+  source lives at `lib/haskell/tests/programs/fib.hs` (the
+  two-cons-cell self-referential fibs definition plus a hand-rolled
+  `zipPlus`). The runner at `lib/haskell/tests/program-fib.sx`
+  mirrors the source as an SX string (the OCaml server's
+  `read-file` lives in the page-helpers env, not the default load
+  env, so direct file reads from inside `eval` aren't available).
+  Tests: `take 15 myFibs == [0,1,1,2,3,5,8,13,21,34,55,89,144,233,377]`,
+  plus a spot-check that the user-defined `zipPlus` is also
+  reachable. Found and fixed an ordering bug in `hk-bind-decls!`:
+  pass 3 (0-arity body evaluation) iterated `(keys groups)` whose
+  order is implementation-defined, so a top-down program where
+  `result = take 15 myFibs` came after `myFibs = …` could see
+  `myFibs` still bound to its `nil` placeholder. Now group names
+  are tracked in source order via a parallel list and pass 3 walks
+  that. 388/388 green.
+
 - **2026-04-25** — Phase 3 do-notation + stub IO monad. Added a
   `hk-desugar-do` pass that follows Haskell 98 §3.14 verbatim:
   `do { e } = e`, `do { e ; ss } = e >> do { ss }`,