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+# Session summary — 2026-10-16: two-phase parse, milestones 2a–2c
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+
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+Branch **`resolve-check`**, HEAD `f500a12`, tags `v3-two-phase-m2a`,
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+`v3-two-phase-m2b`, `v3-two-phase-m2c`. Suite **199/199**; fixpoint
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+**OK (3,620,461 bytes)**; tree clean. Design/record:
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+`docs/plan-two-phase-parse.md`.
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+
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+## Goal
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+
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+Delete `SymTab.FwdVarRef`/`FwdVarName`/`FwdVarResolve`,
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+`Check.NoteForward`/`FlushForward`, the `Design` forward branch and the
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+`Op=1` marker — by parsing a unit's declarations before its procedure
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+bodies, so forward references bind normally.
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+
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+## What landed (all behind `-twophase`, default off)
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+
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+| Step | Commit | What |
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+| --- | --- | --- |
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+| 2a | `dce67fc` | `scanner.SeekTo(p)`: replay `NextCh` over the in-memory buffer (O(p), no I/O); body-span table + a `SeekTo` round-trip fidelity check in the probe. |
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+| 2b | `cdb6436` | `SymTab.DeferReset`/`DeferBody`/`ReenterDeferred`/`ParamName`; `Lower.ReenterScopeProc`/`CurScopeProc`; span table carries the deferral index. |
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+| 2c | `f500a12` | Real deferral: phase-1 `DeferSkip` (leave scanner at the matching `END`, close like `FORWARD`), phase-2 re-parse loop at module ends. |
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+
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+## Mechanism (2c)
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+
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+- **Phase 1** — `DeferSkip` (reached from `Block`, only for plain
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+ `ProcDecl` bodies; methods stay inline) consumes the body tokens for
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+ real, verifies `END <name>`, leaves the scanner at that `END` so
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+ `Block`'s trailing `END ident` consumes it, records the span; then
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+ `ProcDecl` closes the proc like `FORWARD` (`AbortFunc`, no body node).
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+- **Phase 2** — an inlined loop at both module ends
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+ (`ProgModule`/`ImplUnit`) does, per span: `SeekTo`+`Adv`,
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+ `SymTab.ReenterDeferred`, `Lower.ReenterScopeProc`, `QbeGen.BeginFunc`,
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+ `Block(nm)`, attach body + block decls to the proc node,
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+ `ScopeLeave`/`CloseProc`/`EndFunc`. Scanner/parser state and the
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+ unit's own `astDecl`/`astStmt` are saved and restored around the loop.
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+- Opens/closes pair **within each pass**; **registrations run once**
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+ (skip pass); the re-parse uses the resume paths.
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+
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+## Two real bugs found and fixed while landing it
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+
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+1. The re-parse loop **clobbered the unit's `astDecl`/`astStmt`** before
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+ `ProgModule` built the unit (main got a proc's statements). Fixed by
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+ saving/restoring them around the loop.
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+2. `PopPos` restores the scanner's **`errors` counter** (deliberate for
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+ the shadow probe), so it **wiped every diagnostic recorded during the
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+ re-parse** — `210`/`232` etc. inside deferred bodies were silently
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+ dropped (`t_bad_fwd` was wrongly accepted). Fixed by re-instating
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+ the post-loop count after `PopPos`.
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+
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+## Findings worth keeping
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+
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+- **No forward procedure tolerance exists.** A call to a proc declared
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+ later in the same module is `233` (+ a knock-on `201` at EOF); a bare
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+ `P;` two lines early is `233`. The compiler's own sources self-compile
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+ only because each `.mod` is paired with its `.def`, parsed first (so
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+ e.g. `SemError` is declared before `NoteLabel`'s body compiles), plus
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+ strict declaration-before-use inside modules. Consequence for the
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+ grammar: **atg helpers must be declared before use** (`NoteSpan` had to
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+ move above `ProbeBody`); the `FwdVar` tolerance covers module-level
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+ *variables* only.
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+- **Suppressed inline emit = emission only.** Under `SetNoEmit` every
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+ `QbeGen` counter still advances and is discarded per unit by
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+ `RestoreSession`; `Lower`'s tables are permanent session state.
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+- **Byte-identity vs the old default is the wrong gate for forward
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+ code.** Deferral makes a forward variable ordinary, so it compiles
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+ like a normally-ordered one; the legacy `FwdVar` path is the divergent
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+ one (it drops a `loadw`). Deferred output matches the *normal*
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+ codegen and runs correctly.
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+
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+## Measured (2c)
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+
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+- Suite **199/199** — 193 core + gates: `twophase_same`
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+ (`t_nestedproc`, `t_classmethod`) identity; `twophase_run`
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+ (`t_fwdvar`/`t_fwdsel`/`t_fwdprop`) `-> 42`; `twophase_fail`
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+ (`t_bad_fwd`) `incompatible assignment`.
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+- All **142 single-file tests** under `-twophase`: **0 signals**,
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+ **138 byte-identical**. The 4 differing files are exactly the
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+ forward-reference tests.
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+- Sessions `DBasicProg`/`TString`/`Showcase12` byte-identical.
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+- Fixpoint OK (flag off).
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+
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+## Known gap (why it is not flipped)
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+
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+On some multi-module **implementation** sessions (repro:
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+`convtypes.def/.mod conversions.def/.mod`, i.e. `Conversions.mod` inside
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+the Library1 session) `-twophase` records a **spurious `ident expected`**
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+positioned inside a repassed body — while the emitted `.ssa` is
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+**identical** to the default. The repass reaches the correct AST but
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+trips one extra `SynError`. Candidate causes (to pin next): the
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+`pos`/`len` "previous token" model interacting with `SeekTo`, or a
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+construct where the repass consumes one token too many. Reproduction is
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+small and self-contained, so this is the immediate next step; the flip
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+and the `FwdVar*` deletion follow it.
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+
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+## Resume
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+
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+```sh
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+cd .../m2compiler-V3/compiler
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+./build.sh && ./run_tests.sh # 199/199
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+./M2 -twophase ../stdlib/convtypes.def ../stdlib/convtypes.mod \
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+ ../stdlib/conversions.def ../stdlib/conversions.mod
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+# -> spurious ".../conversions.mod:148:3: ident expected"
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+cd .. && ./bootstrap/fixpoint.sh # FIXPOINT OK
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+```
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