# Session summary — 2026-10-04 (c): L3 attempted to completion; parked green

Branch **`ast-stage-c`**.  HEAD **`e8956b2`**.  Suite **182/182**;
self-hosting fixpoint **OK** (**3,147,849 bytes**).  Working tree clean
except the user's `compiler/toto.mod`.

**L3 (procedures) is not enabled** — `Lower.CanLower` still rejects
procedure-bodied units, so the tree stays green.  L0–L2 remain
byte-verified.

## What was achieved (then reverted, because it broke self-hosting)

The L3 *physics* were solved during this session and **did** byte-compare:

- **Durable symbol resolution.**  `SymTab.PopScope` keeps symbol nodes
  allocated (they just become unreachable), so a new read-only
  `LookupAny`/`FindAny` plus `ProcNParAny`/`ParamTypeAny`/
  `ParamIsVarAny`/`ProcUidAny`/`ProcDepthOfAny`/`ProcResAny`/
  `ParamNameAny`/`IsExternalAny` could resolve a name (and a procedure's
  formals) **after its scope closed** — exactly what an end-of-unit
  `Lower` needs.
- **Two real bugs fixed** (also reverted with the rest):
  - `NkProcDecl` op defaulted to `-1`; `CanProc` requires `0` for a
    normal body → every `PROCEDURE` was rejected.  (Fix: set `0` at node
    creation.)
  - `NkCall` child 0 is an `NkDesignator`, not a bare `NkIdent`; calls
    were mangling as `$_0`.  (Fix: `CalleeName` unwraps it.)
- With those, `candiag` and `t_lower3` **byte-compared MATCH** and the
  suite reached **183/183**.

## Why it was parked

The `SymTab` additions **broke self-hosting** and could not be
stabilized within the session:

- `NthParam` was used before its declaration (line ~2258) by the new
  accessors → `invalid call` / `not a RECORD type` cascades under the
  V3-built compiler.  Inlining the plink walk fixed *that* error, but:
- stage 3 of the fixpoint still failed (`M2S.mod:46 not supported yet`).
- Compounding this, an **`ASTDUMP` debug statement was accidentally
  committed** into `M2.atg` in `v3-lower3-wip`, corrupting later builds
  and wasting diagnosis time (now removed on HEAD).

Option 1 (concurrent legacy+`L` emit) is also ruled out: `QbeGen` shares
one buffer and one counter set, so interleaved emitters corrupt the
legacy path (`docs/summary_two-phase-lower3-finding.md`).

## The path forward (recommended)

L3 does **not** need `SymTab` changes.  Do **option 2 via grammar hooks
with zero `SymTab` surface**:

- while each scope is open, have the grammar stash `(name, kind, ty)`
  for locals/params (and procedure signature info) into a **`Lower`-owned
  table**;
- `Lower` resolves through that table, so it works at unit end without
  touching `SymTab` and without concurrent emit.

This reuses all the AST/call/header work already committed in
`v3-lower3-wip` and avoids the self-host fragility that the `SymTab`
additions triggered.

## State / tags

- Tags: `v3-lower0`, `v3-lower1`, `v3-lower2`, `v3-lower3-wip`,
  `v3-lower-eod-2026-10-04`, and this summary's tag.
- L0–L2 byte-compare tests: `t_exit`, `t_arith`, `t_lower1`, `t_lower2`.

## Resume

```sh
cd ~/Projets/Projets-Modula2/MyWork/m2compiler-V3
git checkout ast-stage-c
cd compiler && ./build.sh && ./run_tests.sh   # 182/182
cd .. && ./bootstrap/fixpoint.sh              # FIXPOINT OK
```