# V3 step 3.7 — hardening pass over composites (done 2026-09-22)

Blaise v0.12.0 lesson applied: thin-on-features, fuzz the
bounds/copies/traps/narrowing paths across the suite before
step 4 calls. Suite 68/68 (32 run — incl. 4 trap-aborts — +
36 reject). No new syntax, no new lowering.

## Real bug found and fixed

- **BoundPair outer `IF` missing `END`** (`M2.atg`): the
  `IF invalid THEN ok := FALSE ELSE ... inner IF ... END;`
  action never closed the outer `IF`. gm2 only warned
  (`syntax warning, «END» missing`) and still built, so every
  green tag since 3.1 carried it. Fixed with one `END`; build
  is now warning-free (apart from the known-benign Coco
  TypeBlock LL(1) advisory). Lesson: treat gm2 warnings as
  errors from here on — add a `grep -i warning` gate before
  step 4.

## New coverage (4 tests, all previously unexercised paths)

- `t_charbounds` → 3: `ARRAY ['a'..'c']` bounds + `CHAR`
  variable indexing (BoundPair char path, char index checks).
- `t_bad_varbound` → 230: non-foldable `ARRAY [lo..hi]`
  bounds (ConstInt-fail path).
- `t_bad_manydims` → 230: 9 dimensions (BoundAdd 8-limit,
  pins the bound as specified behavior).
- `t_trap_emptystr` → abort: `s := ""` into a 3-char array
  (pins the equal-count rule for strings — no silent
  truncation, consistent with `t_trap_count`).

## Verified already-covered (no duplicates added)

Set narrowing trap (`t_trap_setspan`), static 222s, deep-copy
independence, `WITH` stacking, cross-span copies, opaque
pointers — all present; audit confirmed no gaps there.

## Incidental

- Removed stray `compiler/src/essai` + `essai.mod` (scratch
  experiment + linked binary, untracked). Note for its author:
  the snippet fails only on the trailing `;` before `END`
  (strict Wirth `StatSeq`, no trailing separator — same rule
  as step 1); otherwise the two string assigns are fine.
- Regenerated `src/M2.lst` committed with the fix.

Deferred (unchanged): enum lowering, `HIGH`/`LEN`, recursive
`DISPOSE`, nil-deref trap, class lowering. Next: step 4 calls.