# V3 step 8.2 — self-compile gaps fixed for `SymTab` (104/104)

Closing the measured step-8.1 gaps so V3 can compile its own sources.
Suite 104/104 (new `t_constfold`), build warning-free.

## What landed

1. **Named-CONST constant folding.** `SymTab` now stores a CONST's
   literal value text (`SetSymVal`/`GetSymVal`, new `val` field);
   the grammar folds a CONST reference to its literal and folds
   integer `+ - * DIV MOD` on two literals (`QbeGen.Fold2`). So
   `ARRAY [0 .. MaxPend - 1]` and friends fold, in bounds,
   subranges, sets, `FOR` limits and expressions. New test
   `tests/t_constfold.mod` (42).

2. **Forward type references in a `TYPE` block.** `POINTER TO X`
   where `X` is declared later now resolves: `SymTab.ForwardType`
   enters an unresolved alias inside a type block, completed by the
   later `TypeItem` via the existing opaque `SetTarget` path
   (`BeginTypeBlock`/`EndTypeBlock` gate it). `TypeIdent` uses it on
   lookup failure instead of erroring 201.

3. **Trailing `;` before a record's `END`.** `RecordType` accepts
   `RECORD fieldlist [;] END` (grammar now `{ ";" [ RecField ] }`).

4. **Qualified type names** (`FileIO.File`). `TypeIdent` accepts
   `Module.Type` via `SymTab.QualType`; a bare module name as a type
   still reports 221.

5. **Capacity.** `MaxTypes` 256→4096, `MaxPend` 64→256,
   `MaxMods` 32→64. The compiler's own sources exceed 256 type
   descriptors (this alone caused ~465 spurious 230s).

6. **Compact zero-filled array data.** `ArrData` emits QBE
   `{ l n, z n*esz }` instead of one `w 0` per element. Emitting a
   million-element `sessBuf`/`nestBufs` element-by-element was the
   apparent "hang" once the type table stopped truncating them.

7. **Source hygiene.** `Resolve` moved ahead of `PushClassScope` in
   `SymTab.mod` (declaration-before-use; ISO-clean).

## Result

`SymTab.def` + `SymTab.mod` now compile **clean** under V3 (0 errors;
verified with a stub program module). `QbeGen` is close:
down from 205/465 errors to **85 `invalid call` + 38 undeclared + 1
`invalid Statement`**, dominated by two remaining gaps:

- **Within-module forward procedure calls** (10 distinct callees:
  `Revive`, `LocAdd`, `ResClass`, `HApp`, `LocFindUp`, `UpAddrOf`,
  `AllocLocal`, `FlushStrings`, `HeapSize`, `ArrData`). gm2 hoists
  these; ISO wants declaration-before-use or `FORWARD`.
- **Single-character string literals** (`"0"`, `"$"`, `"-"`) are
  typed `CHAR`, so passing them to `ARRAY OF CHAR` formals
  (`Cpy(d, "0")`) reports "invalid call". V3 needs context-sensitive
  CHAR/string coercion.

## Files

`compiler/src/{M2.atg,SymTab.def,SymTab.mod,QbeGen.def,QbeGen.mod}`,
`compiler/tests/t_constfold.mod`, `compiler/run_tests.sh`.