# Two-phase refactor — slice 8 (CASE + WITH statements)

Branch `ast-stage-c`.  Suite **178/178**; self-hosting fixpoint **OK**
(**3,021,285 bytes**; slice 7 was 3,016,802).

## What landed

| Statement | AST |
| --- | --- |
| `CASE e OF … END` | `NkCase(selector, arm…)` |
| case alternative | `NkCaseArm(label…, body)` |
| range label `a..b` | `NkSubrange(a, b)` |
| `ELSE` arm | `NkCaseArm` with `op = 1`, child 0 = body |
| `WITH d, … DO … END` | `NkWith(designator…, body)` |

`CASE` and `WITH` build their node **incrementally**, so no local arrays
are needed (and per-invocation state is preserved across nested forms):
`CaseAlt`, `CaseLabel` and `WithItem` take the enclosing node as a value
parameter and append to it.  A body-less alternative resets `astStmt`
first so it never appends a stale node.

## Verified (temporary `AST.Dump` of `astUnit`, then removed)

```modula2
CASE x OF
  1 : x := 1
| 2, 3..5 : x := 2
ELSE x := 9
END;
WITH r DO x := f END
```

produced

- `NkCase(x, [ NkCaseArm(1, Block[x:=1]),
  NkCaseArm(2, Subrange(3,5), Block[x:=2]),
  NkCaseArm(op=1, Block[x:=9]) ])`
- `NkWith(NkDesignator r, Block[ NkAssign(x, f) ])`

## Deliberately deferred

- Imports, `CLASS`, nested modules in the unit AST.
- Brace/set literals and `ResultComp` call suffixes.
- `Lower` + `.ssa` byte-compare.

## Next

Brace/set literals and `ResultComp`; imports/`CLASS`; then the `Lower`
walk.