erlang: binary pattern matching <<...>> (+21 tests)

plans/erlang-on-sx.md

@@ -53,7 +53,7 @@ Core mapping:
 - [x] Tokenizer: atoms (bare + single-quoted), variables (Uppercase/`_`-prefixed), numbers (int, float, `16#HEX`), strings `"..."`, chars `$c`, punct `( ) { } [ ] , ; . : :: ->` — **62/62 tests**
 - [x] Parser: module declarations, `-module`/`-export`/`-import` attributes, function clauses with head patterns + guards + body — **52/52 tests**
 - [x] Expressions: literals, vars, calls, tuples `{...}`, lists `[...|...]`, `if`, `case`, `receive`, `fun`, `try/catch`, operators, precedence
-- [ ] Binaries `<<...>>` — not yet parsed (deferred to Phase 6)
+- [x] Binaries `<<...>>` — landed in Phase 6 (parser + eval + pattern matching)
 - [x] Unit tests in `lib/erlang/tests/parse.sx`
 
 ### Phase 2 — sequential eval + pattern matching + BIFs
@@ -91,7 +91,7 @@ Core mapping:
 
 ### Phase 6 — the rest
 - [x] List comprehensions `[X*2 || X <- L]` — **12 new eval tests**; generators, filters, multiple generators (cartesian), pattern-matching gens (`{ok, V} <- ...`)
-- [ ] Binary pattern matching `<<A:8, B:16>>`
+- [x] Binary pattern matching `<<A:8, B:16>>` — **21 new eval tests**; literal construction, byte/multi-byte segments, `Rest/binary` tail capture, `is_binary/1`, `byte_size/1`
 - [ ] ETS-lite (in-memory tables via SX dicts)
 - [ ] More BIFs — target 200+ test corpus green
 
@@ -99,6 +99,7 @@ Core mapping:
 
 _Newest first._
 
+- **2026-04-25 binary pattern matching green** — Parser additions: `<<...>>` literal/pattern in `er-parse-primary`, segment grammar `Value [: Size] [/ Spec]` (Spec defaults to `integer`, supports `binary` for tail). Critical fix: segment value uses `er-parse-primary` (not `er-parse-expr-prec`) so the trailing `:Size` doesn't get eaten by the postfix `Mod:Fun` remote-call handler. Runtime value: `{:tag "binary" :bytes (list of int 0-255)}`. Construction: integer segments emit big-endian bytes (size in bits, must be multiple of 8); binary-spec segments concatenate. Pattern matching consumes bytes from a cursor at the front, decoding integer segments big-endian, capturing `Rest/binary` tail at the end. Whole-binary length must consume exactly. New BIFs: `is_binary/1`, `byte_size/1`. Binaries participate in `er-equal?` (byte-wise) and format as `<<b1,b2,...>>`. 21 new eval tests: tag/predicate, byte_size for 8/16/32-bit segments, single + multi segment match, three 8-bit, tail rest size + content, badmatch on size mismatch, `=:=` equality, var-driven construction. Total suite 477/477.
 - **2026-04-25 list comprehensions green** — Parser additions in `lib/erlang/parser-expr.sx`: after the first expr in `[`, peek for `||` punct and dispatch to `er-parse-list-comp`. Qualifiers separated by `,`, each one is `Pattern <- Source` (generator) or any expression (filter — disambiguated by absence of `<-`). AST: `{:type "lc" :head E :qualifiers [...]}` with each qualifier `{:kind "gen"/"filter" ...}`. Evaluator (`er-eval-lc` in transpile.sx): right-fold builds the result by walking qualifiers; generators iterate the source list with env snapshot/restore per element so pattern-bound vars don't leak between iterations; filters skip when falsy. Pattern-matching generators are silently skipped on no-match (e.g. `[V || {ok, V} <- ...]`). 12 new eval tests: map double, fold-sum-of-comprehension, length, filter sum, "all filtered", empty source, cartesian, pattern-match gen, nested generators with filter, squares, tuple capture. Total suite 456/456.
 - **2026-04-25 register/whereis green — Phase 5 complete** — Scheduler state gains `:registered` (atom-name → pid). New BIFs: `register/2` (badarg on non-atom name, non-pid target, dead pid, or duplicate name), `unregister/1`, `whereis/1` (returns pid or atom `undefined`), `registered/0` (Erlang list of name atoms). `er-eval-send` for `Name ! Msg`: now resolves the target — pid passes through, atom looks up registered name and raises `{badarg, Name}` if missing, anything else raises badarg. Process death (in `er-sched-step!`) calls `er-unregister-pid!` to drop any registered name before `er-propagate-exit!` so monitor `{'DOWN'}` messages see the cleared registry. 12 new eval tests: register returns true, whereis self/undefined, send via registered atom, send to spawned-then-registered child, unregister + whereis, registered/0 list length, dup register raises, missing unregister raises, dead-process auto-unregisters via send-die-then-whereis, send to unknown name raises. Total suite 444/444. **Phase 5 complete — Phase 6 (list comprehensions, binary patterns, ETS) is the last phase.**
 - **2026-04-25 supervisor (one-for-one) green** — `er-supervisor-source` in `lib/erlang/runtime.sx` is the canonical Erlang text of a minimal supervisor; `er-load-supervisor!` registers it. Implements `start_link(Mod, Args)` (sup process traps exits, calls `Mod:init/1` to get child-spec list, runs `start_child/1` for each which links the spawned pid back to itself), `which_children/1`, `stop/1`. Receive loop dispatches on `{'EXIT', Dead, _Reason}` (restarts only the dead child via `restart/2`, keeps siblings — proper one-for-one), `{'$sup_which', From}` (returns child list), `'$sup_stop'`. Child specs are `{Id, StartFn}` where `StartFn/0` returns the new child's pid. 7 new eval tests: `which_children` for 1- and 3-child sup, child responds to ping, killed child restarted with fresh pid, restarted child still functional, one-for-one isolation (siblings keep their pids), stop returns ok. Total suite 432/432.