# Two-phase refactor — slice 4 (calls, NOT, builtins → AST)

Branch `ast-stage-c`.  Suite **178/178**; self-hosting fixpoint **OK**
(**2,987,484 bytes**; slice 3 was 2,970,007).

## What landed

`Fact` now covers calls, logical `NOT`, and the builtin pseudo-calls
(they build an `NkCall` whose callee is an `NkIdent` naming the builtin).

| Construct | AST |
| --- | --- |
| `P(a, b, …)` | `NkCall` — child 0 = designator `P`, children 1.. = actuals |
| bare `F` / designator | unchanged (`NkDesignator`) |
| `NOT x` / `~ x` | `NkUnary(OpNot, x)` (`OpNot = 14` added to `AST.def`) |
| `CHR` `ORD`/`ORDL` `CAP` `UCHR` `CHR8` `UORD` `ABS` | `NkCall(NkIdent "…", arg)` |
| `ADR` `SIZE`/`TSIZE` `HIGH`/`LEN` `MIN`/`MAX` | `NkCall(NkIdent "…", designator)` |
| `SHIFT`/`ROTATE` | `NkCall(NkIdent "…", target, amount)` |
| `VAL(T, x)` | `NkCall(NkIdent "VAL", NkIdent "T", x)` |

Actual arguments are collected by `ActParam` (each `Expr`'s node into
`astArgs`), and `Fact` folds them into the `NkCall` after `ArgList`.
Node-building actions are inserted *before* each builtin's existing emit
action, so they read the argument node still sitting in `astCur` and then
let the emit code run unchanged.

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

- `P(2,3)` → `NkCall(Ident P, 2, 3)`
- `ABS(-3)` → `NkCall(Ident ABS, Unary(Sub,3))`
- `CHR(65)+1` → `Add(NkCall(Ident CHR,65), 1)`
- `HIGH(a)` → `NkCall(Ident HIGH, NkDesignator a)`
- `VAL(INTEGER, x)` → `NkCall(Ident VAL, Ident INTEGER, NkDesignator x)`
- `SHIFT(s,1)` → `NkCall(Ident SHIFT, NkDesignator s, 1)`
- `x + MIN(x)` → `Add(NkDesignator x, NkCall(Ident MIN, NkDesignator x))`

## Deliberately deferred

- **Brace literals** (`T{…}`) and **set literals** (`{…}`) still leave
  `astCur := NoNode`.
- **`ResultComp` suffixes** after a call (`F()[i]`, `F().f`, `F()^`) are
  not yet nodes (the call itself is).
- `Lower` + `.ssa` byte-compare still not started.

## Next

Statements (`Block`/`Stat`: `NkAssign`/`NkIf`/`NkWhile`/`NkRepeat`/
`NkFor`/`NkCase`/`NkCall`/…), then brace/set literals and `ResultComp`,
then declarations and the `Lower` walk.