docs: feature status at v3-step4 (87/87)

docs/features.md

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+# m2compiler-V3 — feature status (at `v3-step4`, 87/87 green)
+
+Pipeline: Coco/R `M2.atg` (1748 lines, 73 productions) → `gm2`-built
+`M2` → QBE `.ssa` → `qbe` → `cc` → run. `SymTab.mod` 1623 lines,
+`QbeGen.mod` 2193 lines. Regenerate with
+`cd compiler && ./build.sh && ./run_tests.sh`.
+
+Legend: ✅ done · 🔄 partial · ⏸ not started / deferred.
+
+## Lexical / syntax
+- ✅ Classic idents (no `_`), `0x`/`0X` hex (no `H`), reals with `E`
+  exponents, `#` `<` `<=` `>` `>=` `=`, `//` + nested `(* *)`,
+  strings `'…'`/`"…"`, `0x` array bounds.
+- ✅ `NOT`/`AND`/`OR` (no `~`/`&`), unary minus at expr start,
+  no octal `B`/`C` suffixes.
+
+## Types
+- ✅ `INTEGER`/`CARDINAL`/`SHORTINT`/`LONGINT` (one family, QBE `w`),
+  `REAL`/`LONGREAL` (`d`, widened), `BOOLEAN`, `CHAR`.
+- ✅ Named types, aliases, integer/char subranges (folded bounds),
+  enumerations declared (literal *use* is 230).
+- ✅ `ARRAY [lo..hi,…]` (multi-dim) and open `ARRAY OF` formals.
+- ✅ `RECORD` (flat blobs, nested inline, array fields as pointers).
+- ✅ `SET OF` bool/char/subrange (multi-word masks).
+- ✅ `POINTER TO`, `NIL` as a real type.
+- ✅ Opaque `TYPE T;` + completion in the implementation.
+- ⏸ Enums in expressions/CASE labels, variant records, procedure
+  types, `LONGINT` quads.
+
+## Declarations
+- ✅ `CONST` (integer/char/real literals, folded), `VAR`, `TYPE`,
+  `PROCEDURE` headings + bodies, `FORWARD`.
+- ✅ `DEFINITION`/`IMPLEMENTATION` modules, `IMPORT`/`FROM … IMPORT`,
+  `EXPORT` (parsed), nested local `MODULE` (parsed; lowering pending).
+- ✅ Opaque completion; module `BEGIN` init bodies.
+- ⏸ Strict 231 impl-vs-def signature checks (arity checked, types not).
+
+## Statements
+- ✅ Assignment, `IF/ELSIF/ELSE`, `CASE` (labels, ranges, `ELSE`),
+  `WHILE`, `REPEAT/UNTIL`, `LOOP/EXIT`, `FOR/TO/BY` (static sign),
+  `WITH` (single/multi/nested), `RETURN` (232-checked),
+  `NEW`/`DISPOSE` (builtins), bare and parenthesized calls.
+- ⏸ `HIGH`/`LEN`, `GOTO`/labels.
+
+## Expressions
+- ✅ Full precedence, `+ - * / DIV MOD`, comparisons, eager
+  `AND`/`OR`/`NOT`, `IN`, set ops (`+ - * /` = union/diff/inter/symdiff),
+  pointer `=`/`#`, int→real conversion, `^` deref, indexing, field
+  access, qualified `L.x`/`L.P`.
+- ✅ `NIL` comparisons/assignment.
+- ⏸ String `=`/`+`, `VAL`/`ADR`/`TSIZE`/`SIZE` builtins, result
+  suffixes (`F()^`).
+
+## Procedures & modules
+- ✅ Value + `VAR` params, function results, recursion, mutual
+  recursion (`FORWARD`), nested procedures with static-link display
+  (any depth), array/record/set/pointer params, open-array `VAR`
+  formals.
+- ✅ Separate compilation: `lib.def lib.mod prog.mod` → one image;
+  module init functions; opaque completion.
+- ⏸ Procedure-type variables / indirect calls, per-file object
+  emission, import cycles.
+
+## Backend (QBE)
+- ✅ Length-prefixed arrays (count + elements), deep record copy,
+  count-checked whole-array assign, runtime bounds/span traps
+  (`$abort`, rc 134), multi-word sets, `alloc8` heap
+  (`malloc`/`free`), static-link frames, deterministic `%tN`/`@LN`,
+  whole-image buffering.
+- ✅ `REAL` runtime const flush, string literals as descriptors.
+- ⏸ `runtime/syslib/Trap` (traps are `$abort` for now), recursive
+  `DISPOSE`.
+
+## Error codes
+- ✅ 200/201/202, 210–222, 223 (declared), 230, 231, 232,
+  **233 `invalid call`**, plus `file:line:col` console format.
+
+## Not started
+- ⏸ Clarion `CLASS` lowering (declared + checked only), Unicode
+  `UCHAR`/`UString` (locked design, no lexer/backing), `stdlib` /
+  `runtime/syslib` libraries, self-hosting fixpoint. The TopSpeed
+  legacy grammar (`TopSpeed-V3-M2.atg`) is a separate sidecar, not
+  merged.
+
+Next: step 5 — Benjamin stdlib (first real use of separate
+compilation). Roadmap: `docs/plan.md`, `docs/blaise-phases-map.md`.